Running head: The seduction of easiness
The seduction of easiness: How science depictions influence laypeople’s
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reliance on their own evaluation of scientific information 1
Lisa Scharrera*, Rainer Brommea, M. Anne Brittb & Marc Stadtlera
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a
Department of Psychology, University of Muenster, Fliednerstrasse 21, 48149 Muenster,
Germany, Email: lisa.scharrer@uni-muenster.de; bromme@uni-muenster.de; stadtlm@unimuenster.de
b
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Psychology Department, Northern Illinois University, 363 Psychology-Math Building,
Dekalb, IL60115, USA, Email: britt@niu.edu
* Corresponding author: Westfälische Wilhelms-University, Department of Psychology,
Fliednerstrasse 21, 48149 Muenster, Germany. Email: lisa.scharrer@uni-muenster.de; Tel.:
+49 251 8339379; Fax: +49 251 8339105
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1
Part of this work has been published as a contribution to the 33rd annual meeting of the Cognitive Science
Society, 2011, Boston, USA.
Acknowledgments
This research was supported by the Deutsche Forschungsgemeinschaft (DFG), grant
BR1126/6-1.
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Abstract
The present research investigated whether laypeople are inclined to rely on their own
evaluations of the acceptability of scientific claims despite their knowledge limitations.
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Specifically, we tested whether laypeople are more prone to discount their actual dependence
on expert knowledge when they are presented with simplified science texts. In two
experiments, participants read scientific arguments that varied in comprehensibility and type
of argument support and therefore in apparent easiness. We assessed participants’ inclination
to rely on their own evaluation rather than deferring to expert advice when judging argument
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persuasiveness. The results showed that laypeople were more strongly persuaded by
apparently easy arguments than by difficult ones. Furthermore, they were more confident in
their own evaluation of the information and less inclined to turn to an expert for decisionmaking support after reading easy compared to difficult arguments.
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Keywords: knowledge evaluation; expertise; argument comprehensibility; causal
explanations; evidence
1.
Introduction
Laypeople frequently encounter situations where they must make decisions about science45
related issues. Whether making up one’s mind about undergoing a particular medical
treatment or deciding whether certain behaviors are detrimental to the environment, laypeople
must judge scientific claims and the arguments provided to support such claims. While the
Internet has reduced problems of access to scientific information, a major challenge remains
in the evaluation of this information, regarding its acceptability, usefulness and sufficiency
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for solving a problem at hand (Blair & Johnson, 1987; Brand-Gruwel & Stadtler, 2011;
Bromme, Kienhues & Porsch, 2010; Goldman, 2011; Kienhues, Stadtler & Bromme, 2011;
Mason, Ariasi & Boldrin, 2011; Wiley et al., 2009). One reason why evaluation presents such
a challenge lies in the specific nature of science knowledge. Advances in science and
technology have led to enormous growth of scientific knowledge, accompanied by
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specialization and differentiation. To manage this complexity, scientific knowledge is
organized into different disciplines that are represented by specialized experts (Keil, Stein,
Webb, Billings & Rozenblit, 2008), constituting a ‘division of cognitive labor’ (Keil et al.,
2008, Putnam, 1975; Stehr, 1994).
Due to such division of cognitive labor in modern societies, we remain laypeople throughout
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our whole lifetime regarding most topics and domains of science. Laypeople generally lack
the high level of background knowledge and specialized training required to come to a wellfounded decision about the veracity and thus the appropriate persuasiveness of scientific
claims. This is what sets laypeople apart from ‘experts’, who are specifically trained and
experienced in a domain, and from ‘novices’, who are not yet experts, but strive to become
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experts through relevant training and will already have acquired basic domain knowledge and
a certain discipline-based perspective (Bromme, Rambow & Nückles, 2001).
Hence, when laypeople are in a situation which requires them to decide about a complex
science-related issue, they are confronted with a paradox: On the one hand they need to come
to a decision but on the other hand they lack the expert knowledge necessary for making well-
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founded decisions. This problem has been discussed predominately in health and medical
research focusing on patient decision-making. In this context, the ideal of ‘informed decisionmaking’ has been proposed, according to which individuals make their own judgment (for
example about a certain treatment option) only if they have acquired sufficient knowledge and
information about the issue at hand to do so (Bekker et al., 1999; Charles, Gafni & Whelan,
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1997). Such information might be delivered by the expert (the doctor in charge) or the
layperson might find it elsewhere, nowadays mostly on the Internet (Fox, 2005). Even if this
ideal of ‘informed decision-making’ is realized, laypeople must judge if their understanding
of the issue is sufficient, or if it is still necessary to defer to an expert. Judging which of these
two strategies is the appropriate course of action logically requires that the individual can
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correctly assess the sufficiency of their own knowledge for the decision task at hand. In other
words, they have to successfully engage in metacognitive calibration by forming an accurate
awareness of what they know and what they do not know (Glenberg & Epstein, 1985; Pieschl,
2009).
Unfortunately, as Keil (Keil et al., 2010) and his group have shown, laypersons tend to
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overestimate their understanding of complex science- and technology-based issues. If
laypeople fail to recognize their own knowledge limitations they might falsely assume that
their understanding of the gathered information related to a certain knowledge claim enables
them to evaluate the persuasiveness of the claim. As a consequence, they might underestimate
their actual need to defer to an expert to reach a truly informed decision. Conversely, only if
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individuals feel they lack sufficient understanding of the matter should they refrain from
relying on their own evaluations. Ascertaining the conditions under which laypeople become
aware of their own epistemic limitations when they process science-based text information
remains an open empirical question. In this investigation, we are interested in the
characteristics of science texts that might affect the development of such awareness.
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Judging scientific claims is no simple and straightforward act. Persuasiveness itself is a
graded concept. Persuasiveness of arguments can be indicated by intensity of claim
agreement and evaluation of argument strength, two measures that feature prominently in
persuasion research (O’Keefe, 2002). Both can be expected to be closely related but are
nevertheless not equivalent. While lay recipients may perceive the evaluation of argument
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strength as a more abstract, comparably ‘safe’ task without any major consequences,
expressing agreement with a claim must be approached more cautiously, since claim
agreement might be regarded as closely connected to actual behavioral consequences.
To summarize, laypeople’s reliance on their own evaluations should manifest itself in their
inclination to be easily persuaded by provided information. In contrast, if recipients do not
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feel competent to decide about information quality, they should be more hesitant in their
judgments and refrain from indicating a strong opinion. Furthermore, an inclination to rely on
their own evaluations should be reflected even more directly by laypersons’ confidence in
their own decision about a claim. Strong confidence in a decision should manifest itself in
high levels of trust in the own judgment and conversely in a weak desire to turn to an expert
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for decision support. This pattern is consistent with the concept of informed decision-making
(Bekker et al., 1999), which implies that only if recipients feel that they are sufficiently
informed and competent to form an opinion about the subject matter should they let
themselves be persuaded by a given argument.
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1.1 Characteristics of science information
It may be particularly difficult for laypeople to recognize that they should not rely on their
own judgment when they encounter scientific information written in a way that makes the
subject matter appear less complex and easier to evaluate than it actually is. Such is the case
when laypeople read scientific information especially prepared for their consumption, i.e.
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presented in a simplified way in order to make it superficially comprehensible for the lay
public (Kajanne & Pirttilä-Backman, 1999; Wagner, Elejabarrieta & Lahnsteiner, 1995;
Zimmerman, Bisanz, Bisanz, Klein & Klein, 2001). When laypeople encounter simplified
texts, their sense of understanding may mislead them to consider the subject matter easy and
uncomplicated and to judge their mental representations of the described phenomena as more
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complete and accurate than they actually are (cf. Goldman & Bisanz, 2002). Such an
impression may manifest itself in the conviction that their knowledge and skills do not differ
meaningfully from that of an expert in the field. In this case, laypeople would fail to
differentiate between the background knowledge required to comprehend presented
information and the background knowledge required to evaluate the acceptability of the
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information for justifying a given claim. Comprehending simplified information might thus
lead laypeople to regard the described phenomena and mechanisms to be so transparent and
self-evident that they themselves are able to evaluate the information (cf. Keehner & Fischer,
2011) and that deferring to an expert is an unnecessary waste of time and energy. Therefore, if
presented with a simple account, laypeople should be inclined to rely on their own content
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evaluation. If, however, the information is presented in a way that does not conceal the
inherent difficulty of the subject matter, then laypeople should refrain from relying solely on
their own judgement about information persuasiveness (cf. Reber & Schwarz, 1999;
Schwartz, 2004).
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1.2 Influences on perceived easiness of scientific contents
The assumption, that easy information causes recipients to rely more strongly on their own
evaluation of scientific claims, raises the question as to what characteristics make scientific
information appear easy to laypeople. We presume that perceived easiness is influenced by at
least two message characteristics: (1) comprehensibility of the depicted information and (2)
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type of argument support which is presented to back a claim. Our assumption is based on
theoretical considerations from previous literature and empirical findings which show both
characteristics to have an impact on the persuasiveness of arguments (e.g. Brem & Rips,
2000; Eagly, 1974; Slusher & Anderson, 1996).
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1.2.1 Information comprehensibility
Previous findings have shown that people agree more strongly with claims presented as part
of comprehensible arguments than with those that are difficult or impossible to comprehend
(e.g. Bradley & Meeds, 2004; Murphy, Long, Hollerana & Esterly, 2003). However, research
on this issue has mainly dealt with arguments supporting moral claims and arguments
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advertising the usefulness of consumer products. Due to this focus on moral claims and
advertisement, it remains unclear whether the observed comprehensibility effect also applies
to scientific arguments. In fact, the question of whether it generalizes is not trivial. In the case
of moral arguments or arguments intended to advertise everyday products, recipients may
perceive their own values and personal experiences as a sufficient basis for argument
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evaluation. However, in the case of scientific information laypeople might be aware that its
evaluation is usually beyond their capabilities—regardless of whether they feel that they
understand a piece of information. If this is the case, laypeople should not be inclined to agree
more strongly with a scientific claim supported by comprehensible than by incomprehensible
information.
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Two studies did in fact investigate the persuasive effect of comprehensibility for scientific
arguments. While Miller et al. (1976) detected no difference in persuasiveness between
comprehensibility conditions, Eagly (1974) found incomprehensible arguments to cause
weaker claim agreement than comprehensible arguments. However, neither study adequately
answers the question of whether laypeople are more persuaded by arguments they perceive as
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easy. In Miller et al.’s (1976) study, it remains unclear whether the manipulation of
comprehensibility was indeed successful, as no manipulation check was conducted.
Furthermore, Eagly’s (1974) study investigated a situation of expert–novice communication
rather than of expert–layperson communication. Participants (psychology students) were
required to evaluate contents from their own field of study and, due to their prior training,
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may have perceived themselves as principally able to evaluate the given message.
In sum, previous findings on moral issues and advertisement support the notion that
comprehensibility has an influence on argument persuasiveness. However, it is not clear
whether comprehensibility also affects the persuasiveness of scientific arguments and whether
any persuasiveness effects of comprehensibility extend to laypeople’s confidence in their own
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judgments of the provided information.
1.2.2 Type of argument support
Previous research has differentiated between two types of argument support that can back a
causal claim: causal support and empirical support. Causal support explains the mechanism
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underlying the claimed causal connection (e.g. ‘Beta blockers decrease high blood pressure,
because they inhibit the activity of hormones which cause blood pressure-raising stress
reactions in the body.’). In contrast, empirical support backs the claim by referring to relevant
statistical data (e.g. ‘Beta blockers decrease high blood pressure, because blood pressure was
decreased by 20-28% among patients who regularly took beta blockers.’) (for comparable
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distinctions see Brem & Rips, 2000; Koslowski, 1996; Sandoval & Cam, 2011; Slusher &
Anderson, 1996). In other words, whereas causal support answers the question ‘Why are two
concepts causally related?’, empirical support answers the question ‘How do we know that
two concepts are related?’ (Glassner, Weinstock & Neuman, 2005). Kuhn (1991) considers
only evidence (i.e. empirical support) as ‘genuine evidence’ while discounting explanations
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(i.e. causal support) which are not complemented by additional data as ‘pseudoevidence’.
According to Kuhn, explanations serve to establish the plausibility of a claim, which is neither
necessary nor sufficient to supporting its believability. Rather, it is only evidence that
provides direct support for the correctness of a causal claim. This notion is also prevalent in
the empirical sciences, where the most highly regarded justification for claims is empirical
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evidence.
However, despite the prominent role that evidence plays in empirical science, previous
literature regards explanations as a particularly persuasive form of argument support (Gopnik,
2000; Lombrozo, 2006; Trout, 2002) and suggests that laypeople prefer causal support as
claim justifications, possibly because its evaluation is perceived as easier. According to Keil
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(2006, 2010), individuals have a sophisticated sense for causal relations and structure and
seek out explanations. These activities form the essence of individuals’ folk science. Thus,
laypeople may consider causal support as easier to evaluate than empirical support, since
causal support more closely reflects the kinds of claim justifications they consider in everyday
life. This assumption is also in line with Brem and Rips’ (2000) reasoning that explanations
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provide a method for vetting claims by allowing individuals to judge the described
mechanisms for internal coherence and consistency with prior knowledge. Due to allowing
this kind of vetting, laypeople may perceive explanations as adequate subjects for their own
evaluation. Laypeople should therefore be more easily and confidently persuaded by
arguments containing causal support than by arguments containing empirical support.
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The persuasive effect of causal support compared to empirical support has been investigated
in several studies. However, while findings by Slusher and Anderson (1996) indeed confirm
that arguments containing causal support cause greater claim agreement than arguments
containing empirical support, Brem and Rips (2000) conversely found recipients to prefer
evidence over explanations. Similarly, in a study by Sandoval and Cam (2011), 8 to 10 year
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old children were shown to slightly prefer empirical over causal support. Overall, findings on
the persuasive impact of scientific causal and empirical support indicate that there is indeed a
difference in persuasiveness between the two support types. Although theoretical
considerations suggest a persuasive advantage of causal over empirical support from a
layperson’s point of view, results are mixed as to the direction of the persuasive difference. A
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possible explanation for the inconsistency of findings is that type of argument support and
comprehensibility might have been confounded in at least some studies. In cases where
empirical support had been more comprehensible than its causal counterpart, the perceived
easiness of comprehensible support might have outweighed the easiness ascribed to causal
support. Moreover, and similar to the state of affairs regarding comprehensibility, the effect of
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support type on recipients’ confidence in their decision about information persuasiveness has
not been investigated directly. Thus there is a need to assess whether and how support type
influences laypeople’s readiness to rely on their own evaluations.
1.3 The present research
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In two experiments we investigated how features of science depictions influence lay
recipients’ inclination to rely on their own evaluations of scientific information. Therefore, we
investigated how scientific argumentative texts with different levels of comprehensibility and
argument support influence argument persuasiveness and laypeople’s confidence of their
claim agreement decision.
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We expect that if scientific information is presented in a way that makes it difficult for
laypeople to process, they will be more likely to realize that as non-experts they are in fact
unable to decide whether the information poses a sound argument to support a given claim.
Specifically, we hypothesized that recipients would be more intensely persuaded by
comprehensible than incomprehensible arguments. Therefore, reading comprehensible
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arguments should lead to greater agreement with the claim than reading incomprehensible
arguments (hypothesis 1a) and laypeople should evaluate comprehensible arguments as
stronger (i.e. more supportive of the claim) than incomprehensible arguments (hypothesis 1b).
Analogously, based on the assumption that causal support is perceived as easier by laypeople,
arguments containing causal support should be more persuasive than arguments containing
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empirical support. Therefore, we expect that reading causal support will lead to stronger claim
agreement than empirical support (hypothesis 2a) and moreover, that laypeople will evaluate
arguments containing causal support as stronger than those containing empirical support
(hypothesis 2b).
We also expect that laypeople would be more confident in their own decision about the
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acceptability of provided scientific information when information processing is easy than
when it is difficult. Therefore, comprehensible arguments should cause laypeople to have
greater trust in their own decision about the claim (hypothesis 3a) and conversely a weaker
desire to consult an expert for further decision-making support than they would have with
incomprehensible arguments (hypothesis 3b). Similarly, receiving arguments with causal
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support should lead lay recipients to trust more strongly in their own decision about the claim
(hypothesis 4a) and to have a weaker desire to consult an expert than when they receive
arguments with empirical support (hypothesis 4b).
2.
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Experiment I
To investigate our hypotheses, we conducted a first experiment in which participants read
texts about scientific topics which provided support for a claim. The extent to which
laypeople were persuaded by the provided information and their confidence in the claim
agreement decision were assessed.
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2.1 Method
2.1.1 Design and Participants
The experiment was conducted with a 2x2 repeated measures design, the independent
variables being argument comprehensibility (comprehensible vs. incomprehensible) and type
of argument support (causal vs. empirical). Each participant was assigned to all four
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experimental conditions. In each condition, participants were asked to read an argument about
a medical topic. Thus, every recipient read four arguments in total: one comprehensible
argument containing causal support, one comprehensible argument containing empirical
support, one incomprehensible argument containing causal support and one incomprehensible
argument containing empirical support. The order of exposure to experimental conditions was
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counterbalanced among participants by using a Latin square design. Hence, across the sample,
arguments from each condition were equally often presented in each position.
Eighty-eight undergraduates (52 female, 36 male, mean age = 25.66 years, SD = 5.13) of
various majors at a German university took part in the study and received 8 Euros for their
participation. Thus, the sample consisted of adult participants who had undergone at least
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some academic training and who should therefore have developed a generally sophisticated
understanding of the nature of knowledge, making them principally able to appropriately
handle scientific knowledge questions (e.g. King & Kitchener, 1994). To ensure participants’
lay status, students of medicine, biology or related subjects and students of empirical sciences
(including psychology), who can be assumed to be particularly familiar with empirical
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argument support, were excluded from participation.
2.1.2 Materials
Expository texts about four medical issues were created (mean text length = 80.5 words, SD =
16.46). The texts contained concepts and relations that were derived from real-world concepts
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but were by themselves imaginary. The use of imaginary contents was aimed to keep readers’
prior knowledge as low as possible. Furthermore, it should reduce the likelihood that
participants had already formed a strong prior attitude about the specific issues, as prior
attitude has been shown to have an influence on individuals’ agreement with an argument
(Erb, Bohner, Rank & Einwiller, 2002). All texts were written by the first author of this paper,
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with the help of authentic online texts of different types and from various sources that dealt
with related medical issues, for example texts from scientific journals such as European
Journal of Lipid Science and Technology, popularized science texts intended for lay
audiences such as information from www.netdoctor.de (a German website offering
information on various health topics), and websites offering a mixture of simplified contents
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and more specialized in-depth information such as Wikipedia.
Each text consisted of an argument that supported an issue-related causal claim (claim 1:’The
intake of Eratomin leads to a decrease of the blood cholesterol level.’, claim 2: ‘The BurkittVirus causes the development of the Devic Syndrome in the body.’, claim 3: ‘A side-effect of
Rethoxat is that it brings about asthma attacks.’, claim 4: ‘The intake of Lisinorase helps
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against high blood pressure.’). The claim was always stated at the beginning of the argument,
followed by information that acted as claim support. For every text, four variations were
created, analogous to the experimental conditions: In the causal support conditions, the claim
was supported by an explanation of the underlying mechanism and in the empirical support
conditions by statistical data. For example, presented below is the English translation of the
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following four argument versions that support the claim ‘The intake of Eratomin leads to a
decrease of the blood cholesterol level’:
(1) Comprehensible argument containing causal support:
‘The intake of Eratomin leads to a decrease of the blood cholesterol level.
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This is because the body is provided with cholesterol through absorbing it from food.
During the absorption process in the small intestine, specialized proteins split fats that are
contained in the food into cholesterol. Eratomin binds these proteins and by this means,
the proteins lose their ability to split fat molecules. As consequentially the amount of
cholesterol that is absorbed from food is decreased, the amount of cholesterol in the body
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is lowered.’
(2) Incomprehensible argument containing causal support:
‘The intake of Eratomin leads to a decrease of the blood cholesterol level.
This is because cholesterol absorption in the intestinum tenue is controlled by PKA330
regulated lipases. In this process, triacylglycerol from food is split into mono- and
diglycerid as well as cholesterol. Eratomin acts as ligand of carboxylesterase and thus as
competitive inhibitor, because the carboxylesterase-ligand-complex has no hydrolytic
effect. This leads to a reduction of the cholesterol absorption rate and consequentially to a
decrease of the amount of high- and low-density lipoprotein in the sanguis.’
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(3) Comprehensible argument containing empirical support:
‘The intake of Eratomin leads to a decrease of the blood cholesterol level.
This is because studies have shown that after a daily intake of 30mg Eratomin over a
period of six months, blood cholesterol levels are decreased by 20-28%. In contrast,
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among a comparison group of patients who in the same period of time did not take
Eratomin, there was no lowering of cholesterol levels. This was attested by measurements
of the amount of cholesterol in the blood of both patient groups at the beginning and at
the end of the six months period. For this purpose, cholesterol particles were chemically
separated from the other component parts of the blood. The amount of cholesterol in the
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blood could by this means be determined at both times of measurement.’
(4) Incomprehensible argument containing empirical support:
‘The intake of Eratomin leads to a decrease of the blood cholesterol level.
This is because studies among patients have shown a reduction of the amount of large350
bouyant and intermediate-dense as well as triglyceride-rich lipoproteins in the haima after
daily application of 30mg Eratomin over a period of six months by 20-28%. In a verum
free group there was c.p. no decrescence. This resulted from pre and post interventionally
applied capillary electrophoresis on all patients’ sanguis during which the sample
injection of CE (48 nl) was executed hydrodynamically.’
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Comprehensibility of both argument support types was manipulated in three ways. First,
incomprehensible arguments contained unexplained technical terms, whereas in the
comprehensible condition these terms were translated into more familiar words (Nagy, 1988)
(e.g. ‘lipase’ in the incomprehensible condition was replaced by ‘specialized proteins’ in the
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comprehensible condition). Second, incomprehensible support comprised unnecessary,
distracting details, which were not required to support the argument claim (Trabasso, Secco &
van den Broek, 1984) (e.g. the fact that lipase is PKA-regulated). Third, in comprehensible
argument support, important information was repeated. According to Tyler (1994), repetition
contributes to discourse comprehensibility by signaling recipients how to incorporate new
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information into the progressing discourse, thus facilitating perceptions of text coherence (e.g.
‘This is because the body is provided with cholesterol through absorbing it from food. During
the absorption process [...]’; NB repeated information was not underlined in the original
material). However, comprehensibility manipulations were only applied to the argument
support while the claim was stated in the same wording in all conditions.
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Participants were provided with one argument from each experimental condition, whereby
each argument addressed a different medical topic. Before reading each argument,
participants were presented a framing story to provide a context for reading (Stadtler &
Bromme, 2008). In this framing story, the participant was asked to imagine that a good friend
who had a particular medical problem was unsure whether a certain problem-related claim
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was true or false and asked the participant about their opinion. After reading the framing
scenario, participants were asked to imagine that they had researched the Internet for
information to find an answer to the friend’s question. Participants were then presented with
an argument text which dealt with the medical topic described in the scenario, and which they
had allegedly found during their search.
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In each experimental condition, participants were presented with a separate framing scenario,
fitting to the respective medical topic of the argument. In order to keep the social role ascribed
to the online source from which the argument stemmed constant between conditions, each
argument was described as being authored by a medical expert but without providing a name
or any further information about the author. No indication was given to participants that the
385
texts they read in the different conditions were authored by the same source. Rather,
participants should have been deterred from assuming the same author behind every text,
since they were required to imagine themselves in completely different scenarios in every
condition.
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2.1.3 Dependent measures
Manipulation check. To assess whether comprehensibility had been manipulated as intended
between the argument versions, participants evaluated each argument for perceived
comprehensibility on a scale from 1 (‘very incomprehensible’) to 7 (‘very comprehensible’).
Since comprehensibility might be interpreted differently by different readers (Wiley, Griffin
395
& Thiede, 2005), participants were provided with a short definition of what the experimenters
meant by comprehensibility to ensure that each participant judged the arguments by
comparable standards. This definition was formulated as follows, by drawing on components
of Jucks’ (2001) questionnaire to assess laypeople’s perspective on text comprehensibility
(translated from German): ‘By comprehensible we mean that you perceive the text as vivid,
400
that you feel you can distinguish essential from rather unimportant information, that you think
you can judge whether the single statements are consistent and not in conflict with one
another, and that you feel you can clearly and comprehensively understand and connect the
single statements made by the author.’
405
Argument persuasiveness. The extent to which participants were persuaded by the information
contained in the argument texts was measured by two variables:
(1) Claim agreement. Participants’ agreement with each claim was assessed prior and
subsequent to reading the claim-supporting argument. Participants were asked to indicate their
agreement on a 1 (‘I don’t agree at all’) to 7 (‘I totally agree’) scale; the scale did not
410
comprise a separate ‘I don’t know’ option. The pre-measure of claim agreement was
administered to ensure that laypeople’s prior opinion about the claims did not coincidentally
differ between experimental conditions.
(2) Argument strength. Participants were asked to evaluate the strength of each argument on a
1 to 7 scale, where 1 meant ‘the argument provides no support for the claim’ and 7 meant ‘the
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argument provides strong support for the claim’.
Confidence in the claim agreement decision. Participants’ confidence in their own capability
to make a claim agreement decision was indicated by two measures:
(1) Trust in one’s own judgment of the claim correctness. After reading each argument,
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participants indicated on a 1 to 7 scale how strongly they agreed with the statement ‘I am
confident in my own decision about whether it is true that [claim statement inserted]’ (1:
‘don’t agree’, 7: ‘strongly agree’).
(2) Desire to consult an expert for additional decision support. After reading the argument ,
participants were asked how strongly they agreed with the statement ‘Before I decide about
425
whether it is true that [claim statement inserted], I would like to seek further advice from an
expert’ on a 1 to 7 scale (1: ‘don’t agree’, 7: ‘strongly agree’).
2.1.4 Procedure
Data collection took place in group sessions with a maximum of eight participants who
430
worked individually on a booklet containing the arguments and scales for collecting the
dependent measures. The booklet first presented participants with a scenario in which the
fictitious friend’s problem was described and therefore the frame story for the participants’
task to read the argument. The pre-measure of participants’ claim agreement was collected
and then participants read the argument, which they had allegedly found while doing Internet
435
research to find information regarding their friend’s problem. Afterwards, they provided their
post-measure of claim agreement as well as their trust in their own judgment and desire to
consult an expert. This was repeated four times, so that each participant read four arguments,
one of each experimental condition. After the described measures were collected for all four
arguments, readers were presented again with each argument and were asked to evaluate its
440
strength and comprehensibility. Participants then completed a demographic questionnaire and
were finally debriefed about the fictitious nature of the presented arguments. On average, the
session lasted about 45 minutes.
2.2 Results
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Means and standard deviations of the dependent measures as a function of comprehensibility
and argument support type are shown in Table 1; in the text we will additionally refer to
pooled data (estimated marginal means and standard errors) that was used for statistical
analyses. To determine the statistical power achieved when analyzing the data with repeated
measures F-Tests, a post hoc power analyses using G*Power (Faul, Erdfelder, Lang &
450
Buchner, 2007) was conducted. The analysis with alpha error probability set at .05 and
correlations between levels of the repeated measures factors set at zero showed that the design
and sample size of the experiment yielded a power of .91 for detecting medium sized effects (f
= .25 according to Cohen, 1988).
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--- Insert Table 1 about here ---
2.2.1 Test for order effects
First, we tested whether order of argument presentation had any effects on the dependent
measures. By this means we intended to rule out the possibility that the reading of earlier
460
presented arguments supported readers’ understanding of later presented arguments due to
their structural similarity, which might have interfered with our manipulation of argument
comprehensibility. For this purpose, we conducted repeated measures ANOVAs with
argument order (position 1 to 4) as within-participant-factor on scores of comprehensibility,
argument strength, pre- and post-measures of claim agreement, trust in own agreement
465
decision and desire to consult an expert. The results revealed no significant effects of
argument order on any of the dependent variables (all F < 1.96, ns).
2.2.2 Manipulation check: Perceived argument comprehensibility
A repeated measures ANOVA on comprehensibility ratings with the within-participant470
factors comprehensibility (comprehensible vs. incomprehensible) and type of argument
support (causal vs. empirical) yielded a significant main effect of argument
comprehensibility, F(1,87) = 744.053, p < .001, part. η2 = .895. An inspection of group means
revealed that as intended, arguments designed as comprehensible were considered as more
comprehensible (estimated marginal means (EMM) = 6.102, SE = .097) than arguments
475
designed to be incomprehensible (EMM = 2.028, SE = .112). Neither the main effect of
support type nor the support type*comprehensibility interaction was significant (both F(1,87) <
1.9, ns). Thus, the manipulation check confirmed comprehensibility to vary orthogonally to
type of argument support.
480
2.2.3. Argument persuasiveness
We had expected laypeople to be more intensely persuaded after they had read
comprehensible compared to incomprehensible arguments and after they had read causal
argument support compared to empirical support. This should be indicated by greater claim
agreement (hypothesis 1a) and higher ratings of argument strength (hypothesis 1b). Moreover,
485
we had hypothesized that causal argument support leads to greater claim agreement
(hypothesis 2a) and higher ratings of argument strength (hypothesis 2b) compared to
empirical support.
(1) Claim agreement. Our hypotheses with regards to participants’ claim agreement were
tested by subjecting pre-and post-measures of claim agreement to a repeated measures
490
ANOVA. Comprehensibility, argument support type and time of measurement (prior vs.
subsequent to reading the argument) acted as within-participant-factors. Results showed a
significant main effect of time of measurement, F(1,87) = 119.048, p < .001, part. η2 = .578,
which was due to participants agreeing more to the claim after (EMM = 4.969, SE = .092)
than prior to reading the argument (EMM = 3.989, SE = .075). With regards to the influence
495
of comprehensibility on claim agreement, no significant main effect of comprehensibility was
found, F(1,87) = 1.338, ns, but a significant comprehensibility*time of measurement
interaction, F(1,87) = 7.482, p < .01, part. η2 = .079. As a follow-up, separate repeated measures
ANOVAs on the pre- and post-measures of claim agreement were conducted. Results showed
that whereas claim agreement did not differ between comprehensibility conditions prior to
500
argument reception, F(1,87) =.269, ns, there was a significant difference between
comprehensible and incomprehensible arguments after participants had read the argument,
F(1,87) = 5.659, p < .05, part. η2 = .061. In line with our expectations (hypothesis 1a), group
means revealed that agreement with the claim was higher after reading comprehensible
(EMM = 5.08, SE = .101) compared to incomprehensible arguments (EMM = 4.858, SE =
505
.105). In contrast to our expectations regarding the influence of support type (hypotheses 2a),
we found neither a significant main effect of support type, nor a significant interaction of
support type and time of measurement, both F(1, 87) < 2.625, ns. The three-way interaction of
comprehensibility, support type and time of measurement was also not significant, F(1, 87) =
.795, ns.
510
(2) Perceived argument strength. To test our hypotheses regarding argument strength, we
conducted a repeated measures ANOVA on argument strength ratings with comprehensibility
and support type as within-participant-factors. Results revealed a significant main effect of
comprehensibility, F(1,87) = 11.41, p < .001, part. η2 = .562. Descriptive statistics showed that
as expected (hypothesis 1b), lay recipients judged comprehensible arguments as stronger
515
(EMM = 5.506, SE = .107) than incomprehensible arguments (EMM = 3.733, SE = .147).
Furthermore, we found a main effect of support type, F(1,87) = 13.067, p < .001, part. η2 =
.131, which confirmed hypothesis 2b: Arguments containing causal support were rated as
stronger (EMM = 4.892, SE = .125) than arguments containing empirical support (EMM =
4.347, SE = .121). The interaction of comprehensibility and support type did not reach
520
significance, F(1,87) = 1.232, ns.
2.2.4 Confidence in the claim agreement decision
We had furthermore hypothesized laypeople to be more confident in their own decision about
the claim after they had read comprehensible compared to incomprehensible arguments,
525
indicated by a higher trust in their own decision (hypothesis 3a) and a weaker desire to
consult an expert (hypothesis 3b). In addition, we expected causal argument support to lead to
higher levels of trust in one’s own decision (hypothesis 4a) and to a weaker desire to consult
an expert (hypothesis 4b) compared to empirical support.
Pearson’s correlation of both confidence measures showed that trust in the own agreement
530
decision and desire to consult an expert were negatively associated in all experimental
conditions (comprehensible causal: r = -.529, incomprehensible causal: r = -.406,
comprehensible empirical: r = -.418 and incomprehensible empirical: r = -.421; all
correlations were significant at a .01 level).
(1) Trust in own agreement decision. To test our hypotheses about the influence of
535
comprehensibility and support type, we conducted a repeated measures ANOVA on trust
scores with comprehensibility and support type as within-participant-factors.
As to the influence of argument comprehensibility on trust scores, we found that after
argument reception, trust was higher in the comprehensible (EMM = 4.125, SE = .162) than in
the incomprehensible conditions (EMM = 3.483, SE = .177), F(1,87) = 19.424, p < .001, part.
540
η2 = .183, which supports hypothesis 3a. With regards to the influence of support type on trust
in own decision, no significant main effect of support type was yielded, F(1,87) < 1.682, ns,
which is in contrast to our expectations (hypothesis 4a). Finally, the interaction of
comprehensibility, and support type was not significant, F(1, 87) = .127, ns.
(2) Desire to consult an expert. Our hypotheses regarding the desire to consult an expert were
545
tested by conducting a repeated measures ANOVA on desire ratings with comprehensibility
and support type as within-participant-factors. Concerning our expectations for argument
comprehensibility, results showed that, in line with hypothesis 3b, desire to seek out expert
advice was significantly higher after reading incomprehensible (EMM = 6.205, SE = .116)
than comprehensible arguments (EMM = 5.858, SE = .141), F(1, 87) = 7.527, p < .01, part. η2 =
550
.080. However, results revealed no significant differences in desire scores between both
support types, F(1,87) < 3.379, ns. Hypothesis 4b was therefore not confirmed. Finally, no
significant interaction of comprehensibility and support type was found, F(1, 87) = .841, ns.
2.3 Discussion
555
The results obtained in Experiment I show that comprehensibility of scientific texts clearly
influences laypeople’s reliance on their own evaluations of scientific claims. In line with
hypotheses 1a/b, participants were more intensely persuaded by comprehensible than
incomprehensible arguments, which was indicated by a greater inclination to agree with the
argument claim and higher ratings of perceived argument strength. Moreover, as we had
560
expected, laypeople were more confident in their agreement decision after reading
comprehensible arguments. In this case, they showed higher levels of trust in their own
decision about the claim and conversely perceived themselves less in need of additional
expert advice than after reading incomprehensible arguments, thus supporting hypotheses
3a/b.
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Results obtained for type of argument support partly differ from the pattern observed for
comprehensibility. Although in line with hypothesis 2a lay recipients evaluated arguments
containing causal and empirical support differently regarding argument strength, with
arguments containing causal support being slightly preferred, this did not translate to their
actual agreement with the claim or to their confidence in their claim agreement decision.
570
Hypotheses 2b and 4a/b were therefore not supported.
A possible explanation for type of argument support yielding only a small effect on evaluation
of argument strength and no effect at all on claim agreement and confidence in the agreement
decision might be that our participants had difficulties recognizing the difference between
both support types and thus did not perceive one type as easier to evaluate than the other.
575
Previous research indicates that laypeople frequently fail to distinguish between explanations
and evidence (Kuhn, 1991 but see also Brem & Rips, 2000). It therefore remains unclear
whether the observed limited influence of support type is due to laypeople perceiving causal
and empirical support as equally easy to judge or due to laypeople’s failure to recognize the
difference between causal and empirical support.
580
It is important to note that the participants in Experiment I may have already had some
experience in science. On average they were in their 7th semester (M = 7.71, SD = 4.91),
corresponding to the later phase of undergraduate studies, and might have been more familiar
with scientific research methods and empirical evidence than the ‘average layperson’.
Consequently, participants may have had greater awareness of the controversial and tentative
585
nature of scientific findings and attributed a greater value to empirical argument support than
laypersons would who had less or no science exposure. This might have made them generally
resistant to strongly and confidently agreeing with a claim based on only one argument,
regardless of support type and comprehensibility, and this may have reduced variability of
responses between conditions (across conditions, the increase in claim agreement after
590
compared to before reading an argument was below one scale point on average, from M =
3.988 in the pre measure to M = 4.968 in the post measure, as was the decrease in
participants’ desire to ask an expert, from M = 6.63 in the pre measure to M = 6.033 in the
post measure). It remains an open question whether the detected effects might be more
pronounced in a less experienced population. Finally, only medical topics were used as
595
argument contents. Thus we cannot conclude with certainty whether the yielded results only
apply to medical arguments or can be generalized to other scientific domains as well.
3.
Experiment II
We conducted a second experiment which was aimed at replicating the findings of
600
Experiment I, and extended them in three respects. First, in order to clarify whether our
participants are in fact able to recognize causal and empirical support as different support
types, we asked readers to categorize the arguments accordingly. Second, we sought to
investigate whether the effects yielded in Experiment I might be more pronounced in a
population that is scientifically less experienced than the students included in the first sample.
605
Finally, to extend the applicability of our findings beyond a medical context, we included
arguments from a second scientific field, climate research, in our set of materials.
3.1 Method
3.1.1 Design and Participants
610
The same 2x2 repeated measures design was used as in Experiment I, and again all
participants were presented with all four experimental conditions. Each participant read two
medical arguments and two arguments related to the topic of climate-change. The order of
exposure to experimental conditions was counterbalanced between participants by using a
Latin square design. Furthermore, the allocation of arguments to experimental conditions was
615
balanced so that across participants every condition was represented equally often by
arguments of the medical and climate domain.
Eighty-eight undergraduate students (66 female, 22 male, mean age = 21.36 years, SD = 2.84)
participated and received 8 Euros to compensate for their time. Forty participants were firstyear students with various majors at a German university who had begun their studies no
620
longer than one to two months prior to the experiment. The remaining 48 participants were
students of varying subjects at a University of Applied Sciences, an educational institution
whose curricula focus primarily on practical education for a profession and less on
preparation for research. By including university students who had only just begun their
studies as well as students from an educational institution which is less research-focused than
625
general universities, participants should represent a population that is scientifically less
experienced than participants in Experiment I.
3.1.2 Materials
Similar to Experiment I, the materials were written arguments about four imaginary scientific
630
issues (mean text length = 95.88 words, SD = 23.22). Two arguments supported a causal
claim on a medical topic (claim 1: ‘The intake of Periphenol leads to a decrease of the blood
cholesterol level.’, claim 2: ‘The formation of kidney stones is caused by an overfunction of
the adrenal medulla.’), and two arguments supported a causal claim on a topic related to
climate-change (claim 3: ‘High amounts of Aeropine in the environment contribute to the
635
causation of thunderstorms.’, claim 4: ‘The utilization of Soymethanol as fuel contributes to
global warming.’). As in Experiment I, four versions of each argument were created, varying
in comprehensibility and support type. Again, all texts were written by the first author of this
paper based on different types of online texts from various sources that dealt with related
medical and climate issues.
640
Participants were provided with four arguments, one of each experimental condition, and
every argument addressed a different medical or climate-related issue. Each argument text
was again embedded in a framing story. The framing scenarios of climate arguments
described a friend wondering about the environmental friendliness of certain behaviors (e.g.
whether or not using fuel that contains Soymethanol contributes to global warming). After
645
reading the framing scenario, participants were presented with the argument which was
allegedly found by the participant while doing Internet research to find an answer to the
friend’s problem. As in Experiment I, the texts were described as being written by an expert
without providing any further information about the author. Again, participants were given no
indication that the arguments they read in the different experimental conditions originated
650
from the same source.
3.1.3 Dependent measures
The same measures were collected as in Experiment I. Additionally, participants were asked
to judge whether the argument contained (1) causal or (2) empirical support or whether (3)
655
they could not decide between both options. Arguments containing causal support were
defined as describing ‘the processes and mechanisms that lead to the phenomenon mentioned
in the claim’. Arguments containing empirical support were defined as presenting
‘measurement data which were obtained through scientific studies and which show that the
phenomenon mentioned in the claim occurs.’
660
3.1.4 Procedure
The procedure followed that of Experiment I, with the addition that, at the end of the
procedure, participants categorized each text they had read for the type of argument support it
comprised. The session lasted about 45 minutes on average.
665
3.2 Results
Means and standard deviations of the dependent measures as a function of comprehensibility
and argument support type are presented in Table 2. To assess the statistical power of our data
analysis, a post hoc power analyses using G*Power (Faul et al., 2007) was conducted with an
670
alpha error probability of .05 and correlations between levels of the repeated measures factors
set at zero. Results showed that the design and sample size yielded a power of .91 for
detecting medium sized effects (f = .25 according to Cohen, 1988) when calculating repeated
measures F-tests.
--- Insert Table 2 about here ---
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3.2.1 Test for order effects
To check for possible effects of argument presentation on the dependent measures, we
conducted repeated measures ANOVAs with argument order (position 1 to 4) as withinparticipant-factor on scores of comprehensibility, argument strength, pre- and post-measures
680
of claim agreement, trust in own agreement decision and desire to consult an expert.
Analogous to Experiment I, results showed no significant effects of argument order on the
dependent variables (all F < 2.18, ns).
3.2.2 Manipulation check: Perceived argument comprehensibility
685
A repeated measures ANOVA on comprehensibility ratings with the two within-participantfactors comprehensibility (comprehensible vs. incomprehensible) and type of argument
support (causal vs. empirical) revealed a significant main effect of argument
comprehensibility, F(1,87) = 511.888, p < .001, part. η2 = .855. Group means indicate that
arguments intended to be comprehensible were considered as more comprehensible (EMM =
690
5.71, SE = .105) than arguments written to be incomprehensible (EMM = 2.108, SE = .123).
There was neither a significant main effect of support type, F(1,87) = 1.465, ns, nor a
significant support type*comprehensibility interaction, F(1,87) = 1.517, ns, which confirmed
comprehensibility to vary orthogonally to support type.
695
3.2.3 Judgment of argument support type
Regarding the categorization of arguments as containing causal or empirical support,
participants performed well above chance level in all four conditions. Comprehensible
arguments containing causal support were correctly classified in 92.05% of the cases,
incomprehensible arguments containing causal support in 73.86% of the cases,
700
comprehensible arguments containing empirical support in 76.14% of the cases and
incomprehensible arguments containing empirical support in 72.72% of the cases. In the
comprehensible causal and incomprehensible empirical conditions, most errors were due to
readers picking the ‘undecided’ option (comprehensible causal: 4.5%, incomprehensible
empirical: 15.9%). In contrast, in both other conditions, the majority of errors were due to
705
participants misclassifying the support as the wrong type (incomprehensible empirical:
18.2%, comprehensible causal: 19.3%).
3.2.4 Argument persuasiveness
We had expected that laypeople would be more persuaded after reading comprehensible than
710
incomprehensible information, reflected by greater claim agreement (hypothesis 1a) and
higher ratings of argument strength (hypothesis 1b). Similarly, we expected that after reading
an argument containing causal support, laypeople would agree more with the claim
(hypothesis 2a) and rate the arguments as stronger (hypothesis 2b) than after reading an
argument containing empirical support.
715
(1) Claim agreement. Our hypotheses regarding participants’ claim agreement were tested
using a repeated measures ANOVA on pre-and post-measures of participants’ claim
agreement. Comprehensibility, support type and time of measurement (prior vs. subsequent to
argument reception) acted as within-participant factors. A significant main effect of time of
measurement was found, F(1,87) = 76.673, p < .001, part. η2 = .468, due to participants
720
agreeing more to the claim after having read the argument (EMM = 5.026, SE = .114) than
before reading (EMM = 4.116, SE = .088). The analysis yielded no significant main effect of
comprehensibility, F(1, 87) = .758, ns, but a significant comprehensibility*time of measurement
interaction, F(1,87) = 14.926, p < .001, part. η2 = .146. Whereas claim agreement did not differ
between comprehensibility conditions prior to argument reception, F(1,87) = 2.222, ns, there
725
was a significant difference between comprehensible and incomprehensible arguments after
participants had read the argument, F(1,87) = 11.199, p < .001, part. η2 = .114. In line with
hypothesis 1a, agreement with the claim was higher after reading comprehensible (EMM =
5.210, SE = .128) than incomprehensible arguments (EMM = 4.841, SE = .125). However,
there was no significant main effect of support type and no significant interaction of support
730
type and time of measurement, both F(1, 87) < .496, ns. Hypothesis 2a was therefore not
confirmed by our results. Furthermore, results yielded no significant three-way interaction of
comprehensibility, support type and time of measurement, F(1, 87) = .154, ns.
(2) Perceived argument strength. In order to test the hypotheses regarding argument strength,
a repeated measures ANOVA on strength ratings with comprehensibility and support type as
735
within-participant factors was conducted. Results confirmed hypothesis 1b by revealing a
significant main effect of comprehensibility, F(1,87) = 139.020, p < .001, part. η2 = .615:
Across support types, comprehensible arguments were regarded as stronger (EMM = 5.574,
SE = .095) than incomprehensible arguments (EMM = 3.614, SE = .162). As expected in
hypothesis 2b, we also found a significant main effect of support type, F(1,87) = 13.505, p <
740
.001, part. η2 = .134, due to arguments with causal support being rated as stronger (EMM =
4.835, SE = .121) than those with empirical support (EMM = 4.352, SE = .125). The
interaction of comprehensibility and support type was not significant, F(1,87) = .002, ns.
3.2.5 Confidence in the claim agreement decision
745
We had hypothesized that laypeople would be more confident in their own decision about the
claim after reading comprehensible than incomprehensible arguments, which should lead to a
higher trust in their own decision (hypothesis 3a) and a weaker desire for expert advice
(hypothesis 3b). Moreover, we had hypothesized higher levels of trust in one’s own decision
(hypothesis 4a) and a weaker desire to consult an expert (hypothesis 4b) after reading causal
750
compared to empirical support.
As in Experiment I, Pearson’s correlation showed that trust in one’s own agreement decision
and desire to consult an expert were negatively related in all conditions (comprehensible
causal: r = -.383, incomprehensible causal: r = -.476, comprehensible empirical: r = -.420 and
incomprehensible empirical: r = -.577; all correlations were significant at a .01 level).
755
(1) Trust in own agreement decision. To test our hypotheses regarding participants’ trust in
their own decision, a repeated measures ANOVA on trust scores with comprehensibility and
support type as within-participant factors was applied. Regarding the expected influence of
argument comprehensibility, results showed that trust was higher in the comprehensible
(EMM = 4.54, SE = .167) than in the incomprehensible conditions (EMM = 3.483, SE =
760
.165), F(1,87) = 41.465, p < .001, part. η2 = .323, providing support for hypothesis 3a. As to the
influence of type of argument support, results revealed that reading causal and empirical
support led to different levels of trust, F(1,87) = 9.204, p < .01, part. η2 = .096. In line with
hypothesis 4a, participants’ trust in their own decision was higher after reading causal support
(EMM = 4.21, SE = .157) than after reading empirical support (EMM = 3.813, SE = .159).
765
There was finally no significant interaction of comprehensibility and support type, F(1, 87) =
1.668, ns.
(2) Desire to consult an expert. Our hypotheses regarding laypeople’s desire to seek out
expert advice were tested using a repeated measures ANOVA with comprehensibility and
support type as within-participant factors. As to the influence of argument comprehensibility,
770
the results were consistent with hypothesis 3b; laypeople’s desire to consult an expert was
significantly higher after reading incomprehensible (EMM = 5.636, SE = .133) than
comprehensible arguments (EMM = 5.114, SE = .162), F(1, 87) = 21.802, p < .001, part. η2 =
.200. With regards to the hypothesized influence of support type, we found no significant
main effect of support type, F(1, 87) < 1.807, ns. Hypothesis 4b was therefore not supported by
775
our data. Finally, the interaction of comprehensibility and support type did not reach
significance, F(1, 87) = 1.375, ns.
3.3 Discussion
The results of Experiment II demonstrate that participants were able to identify the type of
780
argument support presented. Readers were most successful in correctly classifying
comprehensible arguments containing causal support but were also clearly above chance level
in the three other conditions. Consistent with the results of Experiment I, Experiment II
showed comprehensibility to be an important influence on the persuasiveness of provided
information and confidence in the agreement decision. Comprehensible arguments led again
785
to more pronounced claim agreement and were rated as stronger than incomprehensible
arguments (as expected in hypotheses 1a/b). Moreover, in accordance with hypotheses 3a/b,
laypeople showed higher levels of trust in their own decision about the claim and a weaker
desire for expert advice after reading comprehensible arguments than after reading
incomprehensible ones. The results also revealed slight but inconsistent influences of support
790
type on persuasiveness of the provided information and confidence in the agreement decision.
Although in line with hypothesis 2a laypeople evaluated arguments providing causal support
as slightly stronger than those providing empirical support, this did not translate to their actual
agreement with the claim, thus contradicting hypothesis 2b. Moreover, although participants’
trust in their own decision was higher after reading causal support than after reading empirical
795
support (as predicted in hypothesis 4a), this was not reflected in in a differential desire to
consult an expert depending on what type of argument support they had read (hypothesis 4b).
Despite the similarity between the findings of the two experiments, there are also several
differences, particularly with regards to effect sizes. Compared to the first experiment, the
second experiment yielded stronger effects of comprehensibility on claim agreement (Exp. I:
800
part. η2 = .061 vs. Exp. II: part. η2 = .114), trust in own decision about the claim (Exp. I: part.
η2 = .183 vs. Exp. II: part. η2 =.323) and desire to consult an expert (Exp. I: part. η2 = .080,
Exp. II: part. η2 = .200). Thus, the presumably less scientifically experienced participants in
Experiment II agreed more strongly with the claim, showed greater trust in their own
decisions and perceived themselves less in need of expert advice after reading a
805
comprehensible compared to an incomprehensible argument. Moreover, in contrast to the
results of Experiment I, Experiment II showed that participants trusted more strongly in their
own agreement decision after reading causal compared to empirical support.
4.
810
General Discussion
By presenting participants with texts of varying easiness, the present experiments investigated
whether laypeople are inclined to rely on their own evaluation of scientific claims. We had
expected that laypeople would more clearly and confidently accept information they consider
as easy compared to information that was difficult and complex. Thus, we predicted claim
agreement to be greater and arguments rated stronger when recipients read comprehensible
815
compared to incomprehensible arguments (hypotheses 1a/b), and causally supported
arguments compared to empirically supported ones (hypotheses 2a/b). Moreover we had
expected higher levels of trust in laypeople’s own decisions and conversely a weaker desire to
consult an expert after reading comprehensible compared to incomprehensible arguments
(hypotheses 3a/b) and causal compared to empirical support (hypotheses 4a/b).
820
4.1 Summary of present findings
Both experiments revealed that, as expected in hypotheses 1 a/b, laypeople were more
persuaded by information about scientific contents when the information they had received
was comprehensible than when it was incomprehensible. Moreover, in line with hypotheses
825
3a/b, after reading comprehensible arguments, laypeople showed higher levels of trust in their
own agreement decision and a decreased desire to ask an expert for decision support.
Findings with regards to type of argument support are less conclusive and only partly confirm
our expectations. We found that recipients were indeed able to differentiate between argument
support types, and they evaluated arguments containing causal support as stronger than
830
arguments containing empirical support (in line with hypothesis 2b). However, the influence
of support type did not extend to recipients’ claim agreement or to their desire to consult an
expert (contrary to hypotheses 2a and 4b). Finally, while our expectation that support type
would influence laypeople’s trust in their own decision (hypothesis 4a) was not confirmed in
Experiment I, it did receive support in Experiment II, where participants’ trust scores were
835
higher after reading causal than empirical support. The present finding of causal support being
perceived as stronger than empirical support is consistent with previous research showing that
laypersons do not evaluate arguments in the same way as experts, who prefer empirical
evidence and consider explanations unsubstantiated by data as generally weak or unsupported
(Kuhn, 1991; Slusher & Anderson, 1996). The results also corroborate Keil’s (2010)
840
proposition that reasoning in terms of causal explanation plays a central role in laypeople’s
folk science. An additional contribution of the present work was to ensure that the observed
preference for causal support is not due to a confounding with comprehensibility. A possible
confounding with argument comprehensibility might explain the mixed results obtained in
previous research where comprehensibility had not been controlled, with some studies
845
showing laypeople to favor causal support (e.g. Slusher & Anderson, 1996) and other research
finding a preference for empirical support (e.g. Brem & Rips, 2000). By controlling for
comprehensibility of both support types, the present findings show that laypeople have an
actual preference for causal over empirical support.
Furthermore, the results obtained regarding laypeople’s desire to ask an expert for support
850
suggest that laypeople are generally inclined to make use of the division of cognitive labor
when having to come to decisions about science-related issues. Even when receiving easy
texts, participants’ ratings of their desire to ask an expert did not average below 5 on a scale
from 1 to 7 (with 7 indicating a strong desire). Nevertheless, the decreasing influence of
information comprehensibility on the perceived need for expert advice suggests that an over-
855
simplification of scientific contents might mislead lay recipients to underestimate the
importance of relying on experts.
Overall, the results of both experiments show strong similarities, which indicates the
robustness of the obtained findings and moreover demonstrates that the observed effects are
not specific for the domain of medicine. However, compared to Experiment I, Experiment II
860
yielded stronger differences in laypeople’s decisions depending on the easiness of the
received information. This is in line with our expectation that the influence of perceived
easiness on laypeople’s reliance on their own content evaluations depends on their scientific
experience. The participants of Experiment II, who we assume to have been less aware of the
general complexity and tentativeness of scientific knowledge, appear to have more readily
865
formed the impression that being able to understand information qualified them to decide
about the persuasiveness of knowledge claims.
In sum, our results confirm the hypothesis that laypeople are more inclined to rely on their
own evaluations of scientific contents when they perceive the topic at hand as easy than when
they perceive the issue as beyond their own understanding. Moreover, it seems that though
870
comprehensibility has a strong influence on lay recipients’ impression of content easiness, the
impact of support type is comparatively small. Support type might have a stronger effect on
easiness perceptions among laypeople who are scientifically more naïve than the participants
we included in our experiments. The less familiar laypeople are with empirical evidence, and
thus with evidence that is not part of their naïve folk science, the more difficult they may
875
perceive its evaluation and the more inclined they might be to seek out the help of experts.
4.2 Limitations and future directions
It needs to be borne in mind that the present experiments were conducted on a student sample.
Thus, although our participants did not study subjects directly related to the knowledge claims
880
in question and had only just begun their higher education, their scientific experience was
presumably more extensive than that of the ‘average layperson’. In fact, this renders our
findings more remarkable, as it appears that even individuals who should to some degree be
aware of the general complexity and tentativeness of scientific knowledge are prone to
disregard their own epistemic limitations in light of perceived text easiness.
885
To ensure the lay status of our participants, we not only examined university students with
non-empirical majors (Experiment I), but restricted our selection to students who had only
just begun their higher education or were from a less research-oriented institution
(Experiment II). However, it should be noted that we assumed the participants of each
experiment to differ in their scientific experience due to their educational background.
890
Therefore, we cannot conclude with certainty that the differences in effect sizes between
experiments are indeed due to both samples varying in relevant experience. Future research
could further investigate the impact of scientific experience by assessing laypeople’s
epistemological beliefs, which might become more sophisticated as a function of scientific
training, and compare those individuals who have been confirmed to differ in their beliefs
895
about the nature of scientific knowledge (for information about the relationship between
educational experience and epistemological beliefs see Weinstock & Zviling-Beiser, 2009). In
this context, it would also be an interesting direction for future research to more generally
examine the connection between epistemological beliefs as they are traditionally
conceptualized in research (i.e. as beliefs regarding an individual’s own knowledge) and
900
individuals’ conceptions and utilization of the division of cognitive labor (which is related to
individuals’ beliefs about other people’s knowledge). While a comprehensive theoretical
elaboration of the relationship between epistemological beliefs in the traditional sense and
beliefs about the division of cognitive labor is beyond the scope of this article, the interested
reader is referred to Bromme et al. (2010).
905
Two further limitations concern the text materials applied in the present experiments. First,
comprehensibility of the arguments was varied in three ways: through technical jargon,
inclusion of unnecessary detail and repetition of important information. While this was done
to ensure a strong manipulation of comprehensibility, we cannot conclude with certainty
whether the observed effects are due to all three ways of comprehensibility manipulation or
910
whether they are attributable to only one or two of them. In future research, only one way of
manipulating comprehensibility at a time could be applied in order to disentangle their
respective contributions to the presently obtained effects. Second, the arguments used as
stimulus materials were written by one of the experimenters, who is not a medical or climate
expert. Although great care has been taken to write the texts in a style and wording
915
comparable to genuine medicine and climate-related science texts, it cannot be completely
ruled out that participants perceived the texts as less valid representations of science texts than
would have been the case had the texts been written by actual domain experts.
It also needs to be noted that we manipulated comprehensibility and type of argument
assuming that both factors influence perceived easiness of the provided information, but did
920
not explicitly assess laypeople’s impressions of content easiness. In order to more
conclusively establish the assumed role of perceived easiness as a mediating variable of the
observed effects, easiness perceptions should be measured directly in future experiments.
With regards to the specificity of our findings, we would like to point out that although our
experiments were only focused on laypeople, we do not propose that the observed effects are
925
unique to lay recipients. It is possible that experts or novices would show the same inclination
to more strongly and confidently accept an argument when the information is easy as the
laypeople in our samples. However, we suspect that laypeople may be especially prone to
overestimate their epistemic capabilities as a consequence of receiving an easy text.
Compared to laypeople, experts and novices should be more aware of the complexity of
930
scientific knowledge − especially about the topics they have studied laboriously in order to
become an expert. As a result, they might be less likely to perceive a topic as simple and easy
to evaluate only because a specific depiction of the topic is easy to understand. Whether this
assumption is accurate, however, or whether experts and novices are in fact equally inclined
to more readily accept easy information remains an open empirical question warranting
935
further research.
4.3 Educational implications
Our results have implications for science education as well as for the communication of
science knowledge to laypeople outside of the formal learning context. The finding of
940
laypeople tending to rely more strongly on their own evaluations of scientific contents if the
subject matter is presented in an easy way suggests a limited awareness of the general
complexity and tentativeness of scientific knowledge. Due to this limited awareness,
laypeople appear to be susceptible to belief that their own epistemic capabilities are sufficient
to evaluate the veracity of scientific claims, even though they actually possess little or no
945
relevant prior knowledge about the subject matter. This susceptibility may result from a lack
of appreciation for the need to rely on the division of cognitive labor. Even research and
literature on epistemological beliefs is guided by the idea that it is predominately
epistemologically naïve individuals who accept knowledge from authority, whereas
sophisticated individuals attempt to construct knowledge by themselves (but see Elby &
950
Hammer, 2001 for a criticism of this stance). This is reflected in the dimension ‘source of
knowledge’ of epistemological beliefs theories (e.g. Schommer, 1990), which derives from
the belief that knowledge originates from authority figures such as teachers or experts to the
belief that knowledge is the outcome of inquiry and personal construction (and this pole is
conceived as the most elaborated one).
955
The assumption that independence from external sources is a desirable developmental goal
might on the one hand go back to Piagetian influences on research programs on
epistemological beliefs. In the Piagetian tradition, cognitive development during childhood
has been conceived as being driven predominately by children’s own experiences with their
environment, whereas testimony offered by adults has been dismissed as “providing mere
960
'verbal' knowledge, rather than genuine understanding" (Harris, 2001, p. 495), denying any
educative role of such second-hand information (see Harris, 2001 for a criticism of this view).
On the other hand, the view of authority-independence as a desirable state might be
influenced by the normative ideal of students becoming citizens who make up their own
minds instead of deferring to authorities (Perry, 1979). Such a view implicitly suggests that
965
the optimal way for individuals to handle scientific issues is to overcome the division of
cognitive labor by evaluating information and deciding for themselves, on par with an expert.
This criticism does not apply to all epistemological beliefs researchers (see for example
Chinn, Buckland & Samarapungavan, 2011). King and Kitchener (1994) do not argue for a
rejection of reliance on expert knowledge either, but rather for a critical reflection about
970
experts’ knowledge claims. Nevertheless, even the developmental trajectory underlying their
work emphasizes a development towards cognitive autonomy which implies an independence
of one’s own ideas from external authorities and which might be not realistic. If this
normative ideal, held even by several scientists, is shared by laypeople, it may explain their
readiness to make decisions in situations when they should actually ask an expert for advice.
975
In order to prevent individuals from sharing this belief, it is important to increase awareness
of the specific nature of scientific knowledge, the evaluation of which usually requires years
of specialized training. In this context, laypeople should be sensitized to the central role of the
division of cognitive labor in modern societies. In school, as well as in the course of higher
education, students should learn that oftentimes it is not only acceptable but even desirable to
980
rely on other people rather than attempting to solve a problem on one’s own.
Our findings furthermore suggest that caution should be taken whenever scientific contents
are communicated to laypeople outside of the educational context. Popularized science
reports, i.e. science depictions especially intended for public consumption, are usually
characterized by simplification in order to facilitate the target audience’s content
985
understanding (Goldman & Bisanz, 2002; Zimmerman et al., 2001). However, the present
findings indicate that such a simplification includes the risk of making scientific knowledge
appear less complex and easier to evaluate than it actually is. Of course we do not intend to
propose that laypeople should not be informed about scientific contents in a way that allows
them to understand the central facts. However, we consider it important that popularized
990
science reports not only inform laypeople about scientific contents but also make recipients
aware of the fact that the content information presented is usually not sufficient to allow
confident evaluations of related knowledge claims that may influence their decision making.
5.
995
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Table 1
Means and standard deviations (in brackets) for the dependent measures of Experiment I
perceived comprehensibility, perceived argument strength, agreement with the claim prior
1150
and subsequent to reading the argument, trust in own agreement decision, and desire to
consult an expert as a function of comprehensibility and type of argument support. All scales
ranged from 1 to 7 (with 7 meaning higher scores on the dimension).
Claim
Trust in
Desire for
Argument
Compre-
Argument
agreement
own
expert
condition
hensibility
strength
pre
post
decision
advice
Compr.
6.07
5.85
3.99
5.14
4.22
5.72
causal
(1.10)
(1.28)
(1.08)
(1.22)
(1.87)
(1.63)
Incompr.
2.14
3.93
3.94
4.93
3.63
6.16
causal
(1.36)
(1.59)
(1.01)
(1.16)
(2.03)
(1.29)
Compr.
6.14
5.16
3.94
5.02
4.03
6.00
empirical
(1.14)
(1.56)
(0.99)
(1.15)
(1.85)
(1.36)
Incompr.
1.92
3.50
4.08
4.78
3.34
6.25
empirical
(1.24)
(1.67)
(0.91)
(1.26)
(1.93)
(1.25)
1155
Table 2
Means and standard deviations (in brackets) for the dependent measures of Experiment II
perceived comprehensibility, perceived argument strength, agreement with the claim prior
and subsequent to reading the argument, trust in own agreement decision, and desire to
consult an expert as a function of comprehensibility and type of argument support. All scales
1160
ranged from 1 to 7 (with 7 meaning higher scores on the dimension).
Claim
Trust in
Desire for
Argument
Compre-
Argument
agreement
own
expert
condition
hensibility
strength
pre
post
decision
advice
Compr.
5.86
5.82
4.11
5.38
4.58
5.11
causal
(1.35)
(1.14)
(1.38)
(1.36)
(1.77)
(1.79)
Incompr.
2.10
3.85
4.16
4.80
3.84
5.45
causal
(1.45)
(1.74)
(1.36)
(1.46)
(1.90)
(1.79)
Compr.
5.56
5.33
3.92
5.05
4.50
5.11
empirical
(1.20)
(1.30)
(1.42)
(1.55)
(1.77)
(1.76)
Incompr.
2.11
3.38
4.27
4.89
3.13
5.82
empirical
(1.43)
(1.70)
(1,40)
(1.39)
(1.84)
(1.39)