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Nuances in inoculation: The
role of inoculation approach,
ego‐involvement, and message
processing disposition in resistance
a
b
Michael Pfau , Kyle James Tusing, Waipeng Lee , Linda C.
Godbold, Ascan Koerner, Linda J. Penaloza, Yah‐huei Hong &
Violet Shu‐huei Yang
a
Professor in the School of Journalism and Mass
Communication, University of Wisconsin, Madison
b
Lecturer in the School of Communication Studies, Nanyang
Technological University, Singapore
Version of record first published: 21 May 2009.
To cite this article: Michael Pfau, Kyle James Tusing, Waipeng Lee, Linda C. Godbold,
Ascan Koerner, Linda J. Penaloza, Yah‐huei Hong & Violet Shu‐huei Yang (1997): Nuances in
inoculation: The role of inoculation approach, ego‐involvement, and message processing
disposition in resistance, Communication Quarterly, 45:4, 461-481
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Nuances in Inoculation: The Role of
Inoculation Approach, Ego-Involvement,
and Message Processing
Disposition in Resistance
Michael Pfau, Kyle James Tusing, Waipeng Lee, Linda C. Godbold,
Ascan Koerner, Linda J. Penaloza, Yah-huei Hong, and
Violet Shu-huei Yang
THIS investigation attempted to provide further understanding of the inoculation
model of resistance to influence. It examined the efficacy of inoculation treatments
designed to promote central versus peripheral message processing in instilling
resistance to influence, taking into account message processing disposition. The
study also tested the potential of social judgment theory to explain the cognitive
process which occurs in inoculation. A total of 790 participants took part in the
investigation. The study employed three issues that represented low, moderate, and
high involvement, and featured multiple inoculation and attack messages. The
results indicate that inoculation treatments, using central and peripheral
approaches, confer resistance to influence and, thus, imply that threat is more
prominent than refutational preemption in the process of resistance. Further, the
pattern of results suggest that greater receiver need for cognition enhances
resistance, but only with highly involving issues. Finally, the results of the
investigation rule out assimilation and contrast as a potential explanation of the
cognitive process triggered via threat, but suggest that receiver ego-involvement
facilitates threat.
KEY CONCEPTS inoculation, resistance, ego-involvement, message
elaboration, ELM, influence
Michael Pfau (Ph.D., University of Arizona, 1987) is a Professor in the School
of Journalism and Mass Communication, University of Wisconsin—Madison.
Waipeng Lee (Ph.D., University of Wisconsin, 1997)is a Lecturer in the School
of Communication Studies, Nanyang Technological University, Singapore. At
the time this study was conducted, Linda J. Penaloza, Yah-huei Hong, and
Violet Shu-huei Yang were graduate students in Journalism and Mass
Communication, whereas Kyle James Tusing, Linda C. Godbold, and Ascan
F. Koerner were graduate students in Communication Arts, at the University
of Wisconsin—Madison. The authors thank faculty in the School of Journalism
and Mass Communication, Department of Communication Arts, and the
School of Business at the University of Wisconsin—Madison for assistance in
recruiting subjects for this study.
Communication Quarterly, Vol. 45, No 4, Fall 1997, Pages 461-481
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I
n recent years there has been a resurgence of interest in the inoculation approach
of resistance to attitude change. This renewed interest has been primarily
pragmatic in emphasis, with scholars and practitioners exploring applications of
inoculation in commercial, political, and adolescent health contexts. Yet, there has
been little theoretical work on the core inoculation construct (Eagly & Chaiken, 1993).
This investigation sought to refine and extend the core assumptions of inoculation,
thereby providing greater .nuance in inoculation's predictions in future settings.
Specifically, this investigation focussed on the process of inoculation. Research
clearly indicates that inoculation confers resistance to subsequent influence, but
exactly how? Threat and refutational preemption are central concepts in the
inoculation process (McGuire & Papageorgis, 1962; Pfau, 1997), which raises a number
of key questions. What is the relationship between ego-involvement and the core
concepts of threat and refutational preemption? What cognitive processes are
triggered via threat, and what implications do they pose for the type of inoculation
message that is most effective with people who differ in message processing
disposition? These and other issues remain unresolved.
Inoculation Approach and Receiver Processing Disposition
Much more needs to be learned concerning the refutational preemption
component of inoculation treatments, particularly as it relates to receiver processing
disposition. Little is known about the relative efficacy of distinctive inoculation
treatment approaches, except that refutational same and different messages are
comparable in their effectiveness (McGuire, 1961,1962,1966; McGuire & Papageorgis,
1961; Pfau, 1992; Pfau & Burgoon, 1988; Pfau, Kenski, Nitz, & Sorenson, 1990; Pfau,
Tusing, Koerner, Lee, Godbold, Penaloza, Yang, & Hong, 1997).
Beyond comparisons of same and different treatments, which were important in
the early evolution of inoculation theory since they provided implicit documentation
of the integral role threat plays in the process of resistance (Pfau, 1997), there has been
very little research concerning inoculation treatment approach, and none exploring
treatment approach in conjunction with message processing disposition.
The involvement and message processing literature offers a rationale for
examining treatment approach in conjunction with receiver processing proclivity.
The theory and research here identifies two routes to influence: one that is more
thoughtful, featuring active elaboration of message content; and the other less
thoughtful, with an emphasis on simple inferences derived from cues attached to the
messages, such as affect and source. When placed in theoretical context, the two routes
are identified as "central" and "peripheral" in the ELM (see Petty & Cacioppo, 1986).
Inoculation is assumed to be an active process. The threat component of an
inoculation treatment motivates the receiver to engage in bolstering of attitudes against
potential challenges, whereas the refutational preemption component identifies specific
counterarguments and then provides the reasoning and evidence to refute them. The
process of inoculation, which Eagly and Chaiken (1993, p. 564) characterize in terms of
"covert counterarguing," is thus assumed to be active (McGuire, 1964). Inoculation
works by motivating receivers to engage in issue-relevant thought, both concerning the
specific arguments that are noted and refuted in the inoculation treatment as well as
additional arguments that a receiver identifies on his/her own.
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Inoculation presupposes careful elaboration of the arguments and evidence
contained in a treatment message. One recent study found that, absent adequate
message elaboration, in this case as a result of distraction following administration of
treatments, inoculation was precluded (Chen, Reardon, Rea, & Moore, 1991). We
argue that the active process of inoculation corresponds to the type of mindful message
processing identified in the ELM as "central." Inoculation treatments by their very
nature confront the individual with challenges to attitudes, providing both the
motivation and specific content to bolster attitudes. They resemble "incongruent
messages," which Maheswaran and Chaiken (1991) found are more likely to result in
systematic information processing. Furthermore, once threat is triggered, messages
which contain peripheral cues may undermine issue-relevant thinking, which
parallels research findings for high involvement conditions (Petty & Cacioppo, 1986;
Petty, Cacioppo, & Heesacker, 1981). Thus, the efficacy of inoculation treatments
should be enhanced via treatment messages that place greater emphasis on reasoning
and evidence, which are targeted to receivers disposed to more active message
processing.
HI:
Inoculation treatments which are constructed so as to
promote central message processing are superior to those
constructed to promote peripheral processing in conferring
resistance to persuasive attacks for those people who receive
an inoculative treatment as opposed to those who do not
What determines whether receivers engage in more active or mindful message
processing? An individual's need for cognition may be the best predictor of message
processing tendencies. An individual higher in need for cognition expends more
cognitive effort evaluating message content (Cacioppo, Petty, Feinstein, & Jarvis,
1996), which facilitates both comprehension (Cacioppo et al., 1996) and influence of
message content (Cacioppo, Petty, & Morris, 1983). Conversely, receivers lower in
need for cognition are more likely to turn to "extrinsic persuasive cues" (Chaiken,
1987) in evaluating messages. Thus, this study predicts that
H2:
Inoculation confers more resistance to persuasive attacks
among those people who receive an inoculative treatment
who are higher in need for cognition.
The Role of Ego-Involvement
McGuire grounded inoculation on axioms of persuasion that were prevalent
during the 1950s (e.g., selective exposure), but was somewhat tentative concerning the
internal processes that inoculation unleashes. McGuire identified the concepts of
threat and refutational preemption as core axioms in inoculation theory. Threat,
which is defined as receiver acknowledgment of potential susceptibility of attitudes to
subsequent influence, functions as the motivational catalyst to resistance, whereas
refutational preemption provides specific content for receivers to employ in order to
strengthen attitudes against change.
What cognitive process does threat trigger in receivers that fosters resistance to
same and different counterarguments? One plausible explanation is assimilation and
contrast, which have their origins in social judgment theory (Sherif & Hovland, 1961;
Nuances in Inoculation
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Shérif & Shérif, 1967; Shérif, Shérif, & Nebergall, 1965). The theory conceptualizes
attitude based on an evaluative continuum divided into three parts or latitudes:
acceptance, rejection, and noncommitment The latitude of acceptance includes
positions a receiver finds acceptable in comparison with their own view, whereas
latitude of rejection encompasses positions a receiver finds unacceptable. The latitude
of noncommitment features those positions a person finds neither acceptable nor
unacceptable.
In social judgment theory, persuasion is viewed as a two-stage judgmental process
(Smith, 1982). Upon exposure to a persuasive message, the receiver views the message
in terms of their initial attitudinal position, which serves as an "anchor." Initially, if
the message falls within the range of acceptance or rejection, there is a tendency to
distort the message's content Respondents tend to minimize a discrepancy between
the anchor and a message when the latter falls in the range of acceptance, but
maximize a discrepancy when the message falls in the range of rejection.
Subsequently, attitude change is a function of the discrepancy between the message
and the anchor, resulting in the movement of the anchor toward the message in the
event that a message falls within the ranges of acceptance or noncommitment
(assimilation), or in the movement of the anchor away from the message in the event
that it falls in the range of rejection (contrast). Assimilation facilitates influence,
whereas contrast inhibits influence, and may produce a boomerang effect (Kiesler,
Collins, & Miller, 1969).
The division of the evaluative continuum depends entirely on receiver egoinvolvement in the content area. Sherif and Cantril define ego-involvement as
receiver identification with an attitude. An ego-involved attitude is internalized as
part of a person's value system. It is perceived as part of one's self: "as being part of me"
(Sherif & Cantril, 1947, p. 93). An ego-involved attitude is "...inextricably linked to
other aspects of the self...to important group memberships and identifications" (Eagly
& Chaiken, 1993, p. 369). Greater ego-involvement in an issue reduces the range of
noncommitment, extends the range of rejection, and thus enhances the prospect that
a message will invoke the process of contrast (Sherif, Taub, & Hovland, 1958).
Inoculation treatments, because they contain content which is consistent with
existing attitudes, should locate within the receiver's range of acceptance. Thus, an
inoculation treatment initially should trigger assimilation, in which the receiver's
attitude shifts even further toward the position advocated in the message. The
refutational preemption component of the inoculation message would be responsible
for this assimilation effect
In addition, the threat component of an inoculation message provides an
additional contribution. The threatening material should magnify receiver egoinvolvement, which generates sizable discomfort in receivers (Eagly & Chaiken, 1993).
Higher levels of ego-involvement should extend the range of rejection, which contains
beliefs viewed as unacceptable (Sherif & Sherif, 1967).
In this manner, inoculation treatments may simultaneously strengthen existing
attitudes and lay a foundation for subsequent resistance. The effect of the initial shift
in attitudes which is produced by the treatment, and to an even greater degree, the
extension of the latitude of rejection caused by the threatening material, combine to
confer resistance to influence. Thus, when a person subsequently encounters an attack
message, it triggers an even more pronounced contrast effect, and therefore greater
distortion of the attack message, and thus more resistance to it
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The assimilation and contrast explanation for the process of inoculation has
received limited attention to date. The only empirical test of assimilation and contrast
in inoculation was provided fay Manís and Blake (1963), who found that subjects who
received passive immunizations were more resistant to influence. They also found that
immunized subjects distorted the content of subsequent attacks in the direction of the
inoculation treatment
To test for assimilation and contrast, this study examined attitudes at two points
in time: immediately after administration of inoculation treatments, and once again,
following exposure to the attack materials. This study posits that, immediately after
administration of inoculation treatments:
H3:
H4:
Inoculation immediately strengthens the existing attitudes of
those people who receive an inoculative treatment as
compared to those who do not.
The proclivity of inoculation to immediately strengthen
existing attitudes is the most pronounced among more egoinvolved receivers.
However, following exposure to the attack materials, the study predicts that
H5:
Inoculation subsequently confers resistance to persuasive
attacks among those people who receive an inoculative
treatment as compared to those who do not
The concept of ego-involvement is not restricted to use in social judgment theory.
Ego-involvement is defined in a broader sense as personal relevance of a content area
to an individual (Greenwald, 1982). Personal relevance determines the energy an
individual expends in message processing. As Petty and Cacioppo (1986, p. 149)
observe: "Personal relevance enhances motivation to process issue-relevant
arguments."
As a result, more receiver ego-involvement should facilitate the efficacy of
inoculation treatments in conferring resistance to subsequent attacks, independent of
the explanatory mechanisms of assimilation and contrast The more ego-involved in
a content area, the more likely that an individual will be able to access relevant
attitudes (Fazio, 1989). This should facilitate threat, which requires that receivers
perceive potential vulnerability of attitudes. It is the threatening component of
inoculation which motivates the individual to expend the cognitive energy required
to bolster attitudes (Pfau, 1997). This rationale is consistent with the notion that
cognition requires effort, and since people tend to act economically, they are unlikely
to expend cognitive energy attempting to strengthen unimportant attitudes. This is the
same reasoning that underlies the ELM and the HSM, both of which have received
considerable support in extant research (e.g., Chaiken, 1980; Chaiken, Liberman, &
Eagly, 1989; Johnson & Eagly, 1989; Petty & Cacioppo, 1979, 1984,1986, 1990; Petty,
Cacioppo, & Goldman, 1981). This study predicts:
H6:
H7:
The tendency of inoculation to generate threat is most
pronounced among more ego-involved receivers.
The tendency of inoculation to confer resistance to persuasive
Nuances in Inoculation
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attacks is most pronounced among more ego-involved
receivers.
METHOD
Topic Selection
This investigation required three issues, representing low, moderate, and high
issue involvement, and reflecting a roughly equal distribution of opinion both for and
against Use of the concept issue involvement, in contrast to ego-involvement, was
limited to the topic selection phase of the study. For purposes of topic selection, issue
involvement was operationalized as the importance or salience of the issue to the
receiver.
Researchers brainstormed possible topics, preparing policy propositions on 31
topics. After lengthy discussion, researchers settled on 16 policy propositions that
seemed to meet criteria described above. The 16 propositions were included in a survey
instrument designed to measure issue involvement and distribution of opinion. A total
of three 10-interval scales were employed to assess a person's issue involvement in
each topic, adapted from an instrument originally developed by Traylor (1981) to
gauge product involvement. The scale items included: importance of the issue, interest
in the issue, and relevance of the issue. The distribution of opinion was assessed using
a single item: agree, disagree, or neutral/no opinion.
The survey was administered to 118 university undergraduate students (the same
population that was scheduled to be the focus of the subsequent study). Results of the
survey revealed three topics that meet the criteria, representing low, moderate, and
high issue involvement, and reflecting roughly equal distribution of opinion both for
and against the proposition. Final topics selected for the study included: whether
manufacture, sale, and possession of handguns should be banned throughout the
nation (involvement mean: 7.52 on a 1-10-point issue involvement scale); whether the
U. S. should legalize the sale and use of marijuana (involvement mean: 5.95); and if
gambling should be completely legalized throughout the U. S. (involvement mean:
4.77).
Participants
Participants were recruited from introductory courses in three departments at a
midwestern university. The study featured three distinct phases extending over a
period of three weeks. A total of 790 subjects completed all three phases (a retention
rate of 82.7%).
Design, Independent Variables, and Covariates
The investigation employed a 3 X 2 factorial design. The independent variables
included experimental condition and need for cognition. Experimental condition was
operationalized as cognitive inoculation treatment, peripheral treatment, and no
inoculation (control). Effectiveness of inoculative treatments in deflecting the
influence of persuasive attacks was gauged by comparing receiver attitudes following
exposure to the attack, and by examining the amount of attitude change induced by the
attack.
Receiver need for cognition was operationalized according to responses on
Cacioppo, Petty, and Kao's (1984) abbreviated need for cognition scale (NCS). NCS is
designed to "distinguish" those people "who dispositionally tend to engage in and
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enjoy effortful analytic activity" from others (Cacioppo et al., 1983, p. 806). The
shortened 18-item version of the NCS has been found to relate very positively with its
more lengthy 34-item parent (Cacioppo et al., 1984). Receiver need for cognition scores
were subsequently dichotomized based on a median split.
Receiver ego-involvement was treated as a covariate. Ego-involvement was
operationalized in terms of identification with partisan interest groups which
advocate a position consistent with a receiver's attitude. Sherif and colleagues
operationalized ego-involvement in their research as "subjects memberships in or
identification with groups that were known to actively support particular positions
on...issues" (Eagly & Chaiken, 1993, p. 369). This study employed a method of
determining ego-involvement previously used by Perloff (1989). Receiver group
identification was evaluated by asking: on a scale of 0 to 100, where 0 denotes no
identification and 100 indicates very strong identification, to what extent a person
identifies with partisan organizations who advocate positions consistent with their
attitudes.
Procedures
Researchers prepared a number of messages for administration during the study.
Two attack messages were written for each of the three topics: one opposing the thesis
of the proposition, to be administered to subjects who favored the proposition; and one
favoring the thesis of the proposition, to be administered those who opposed it Each
attack message was developed employing two distinct lines of argument, with each
argument supported using an equal portion of substantive (general statistics and
studies) and peripheral (source credibility and anecdotes) backing. The six attack
messages ranged in length from 401 to 406 words.
Four inoculation treatment messages were written in response to each attack
message: two central inoculation messages and two peripheral inoculation messages.
The central inoculation messages contained highly cognitive content, featuring
arguments supported by statistics and studies. The peripheral inoculation treatments
employed a combination of affect and source appeals, featuring arguments supported
by anecdotes and source expertise.
The first paragraph of each inoculation message contained the threat component
Threat was operationalized as a warning of impending potentially persuasive attacks
against the position on the topic supported by the receiver. The rest of the inoculation
message featured answers to arguments that could be raised in a potential attack, with
central messages using highly cognitive content and peripheral messages using a
combination of affect and source appeals. The 24 inoculation messages ranged in
length from 249 to 256 words. An example featuring one of the attack messages and its
four corresponding inoculation messages are included in the appendix.
Each inoculation message attempted to replicate the written style of its
corresponding attack message. The four inoculation messages and corresponding
attack message were constructed to closely match in writing style and
comprehensibility. Special attention was paid to message length, average sentence
length, verb tenses, modifiers, and argument style. Each message was rated for overall
compressibility using Becker, Bavelas, and Braden's (1961) Index of Contingency. The
ratings for the 24 inoculation and six attack messages ranged from 13.8 to 14.8,
suggesting equivalence.
The study was conducted in three phases from November 7 to December 3. During
Nuances in Inoculation
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the first phase, all participants completed a questionnaire designed to provide
demographic information and to assess issue involvement, ego-involvement, and
attitudes about each of the three propositions. Participants were then assigned to
specific conditions based on attitude and issue involvement Participants were told
they were participating in a study about message processing. Phase 1 was
administered over two days.
Issue involvement was operationalized as the importance or salience of the topic.
It was measured using slight modification of the Personal Involvement Inventory,
which is a unidimensional scale, developed and then tested for validity and reliability
by Zaichkowsky (1985). The PH examines "perceived relevance based on personal
needs and interests" (Rubin, 1994, p. 286), and research indicates that it is a valid
(Goldsmith & Emmert, 1991; Zaichkowsky, 1985) and reliable (Celuch & Evans, 1989;
Mobley, Bearden, & Teel, 1988) measure of issue involvement The Pu items that
concern desirability, and are thus more appropriate for product involvement, were
eliminated in this study, and scale intervals were expanded from seven to nine. Scale
items included: boring/interesting, unimportant/important, doesn't/does matter to
me, nonessential/essential, of no concern/of much concern, means nothing/ means a
lot, exciting/unexciting, irrelevant/relevant, superfluous/vital, trivial/fundamental, mundane/fascinating, and significant/insignificant The modified PH involvement scale achieved high reliabilities: on handguns, .94; on marijuana, .94; and on
gambling, .95.
Following Phase 1, researchers entered the preliminary data, analyzed issue
involvement and attitude data, and then on the basis of the results, assigned
participants to conditions. Issue involvement was trichotomized on each topic, and
subjects scores examined. Where a person ranked the same (low, moderate, or high
involvement) on two of the topics on which their overall attitude scores were either
less than 4.5 or greater than 5.5 (on a 1-9-point attitude scale), therefore suggesting the
presence of an attitude for or against a topic, they were assigned to those topics.
Otherwise, participants were assigned randomly to one of the topics on which they
displayed an attitude.
Once assigned to one or two topics, the participants were randomly assigned to
inoculation same, inoculation different, or control condition. Phase 2 and 3
experimental booklets were prepared for each participant The Phase 2 booklets
contained inoculation message(s) supporting ata'tudinal positions for those
participants assigned to same or different treatment conditions, as well as
questionnaires designed to assess threat, attitudes, counterarguments, and answers to
counterarguments on each topic. Phase 3 booklets contained one or two attack
messages opposing attitudinal positions and questionnaires designed to evaluate
participant response to the attack(s).
The second phase included the administration of inoculation materials for treated
participants and additional measurement, and was conducted during November 10 to
22. The third phase of the study featured the administration of attack messages to all
participants and further measurement, and was conducted from November 23 to
December 3.
Dependent Measures
Three dependent measures were employed in the investigation. Attitude was
assessed with six bipolar adjective pairs previously used by Burgoon, Cohen, Miller,
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and Montgomery (1978), Miller and Burgoon (1979), Pfau and Burgoon (1988), and
Pfau, Van Bockern, and Kang (1992). Adjective pairs were: foolish/wise, wrong/right,
unfavorable/favorable, bad/good, unacceptable/acceptable, and negative/positive.
The coefficient alpha reliabilities for the attitude scale were good: handguns, .96;
marijuana, .94; and gambling, .94.
The threat of inoculation treatments was assessed using five bipolar adjective
pairs employed previously by Pfau and Burgoon (1988), Pfau et al. (1990), Pfau (1992),
and Pfau et al. (1992). Threat was measured during Phase 2. Inoculated and control
participants were asked their reaction to the prospect that they may come in contact
with information which may cause them to rethink their position on the issue in
question (which inoculated participants had just been warned about in the treatment
message). The scale items included: nonthreatening/threatening, unintimidating/
intimidating, not harmful/harmful, safe/dangerous, and not risky/risky. The overall
reliabilities of the threat scales were very good: .97 for handguns, .96 for marijuana,
and .95 for gambling.
The final measure involved responses to counterarguments, which participants
listed following their exposure to inoculation materials during Phase 2. After
indicating their attitudes about a message, respondents were asked to identify possible
arguments that were contrary to their own position and to list potential responses to
those arguments in the spaces provided, employing a technique similar to the
thought-listing procedure developed by Petty, Wells, and Brock (1976). Responses
were subsequently coded by three researchers. Coders were instructed to count
declarative statements refuting specific counterarguments as answers. One unique
idea per space which met this criteria was counted, using a scoring method similar to
one used previously by Brock (1967) and Petty et al. (1976).
Researchers spent approximately two hours discussing rating procedure, and then
participated in supervised practice sessions. Inter-coder reliability was assessed using
Rosenthal's effective reliability method (Rosenthal, 1987). Inter-coder reliability
ratings for responses to arguments contrary to attitudes were: for handguns, .97; for
marijuana, .98; and for gambling, .94.
RESULTS
Manipulation Checks
Two manipulation checks were employed as a precondition to all subsequent
analyses to confirm effectiveness of inoculation treatments and the presence of
sufficient threat levels across the three topics/C
Planned comparisons, employing Dunn's multiple comparison procedure (Kirk,
1982) were computed across the inoculation and control conditions on receiver
attitude and threat on the three topics. Results confirmed the effectiveness of the
inoculation and threat manipulations. The inoculated subjects demonstrated greater
resistance to the influence of persuasive attacks across the topics of handguns, F(l,403)
= 34.97, p < .001, eta2 = .09; marijuana, F(l,421) = 52.17, p < .001, eta2 = .13; and gambling,
F(l,396) = 24.25, p < .001, eta2 = .06. In addition, inoculated subjects manifested higher
threat levels for handguns, F(l,400) = 19.68, p < .001, eta2 = .05; marijuana, F(l,427)
= 7.10, p < .05, eta2 = .02; and gambling, F(l,397) = 39.25, p < .001, eta2 = .10. Inoculation
and threat means are depicted in Table 1.
Nuances in Inoculation
469
TABLE 1
Summary of the Threat and Attitude toward the Attack Message Means among Inoculated and Control
Subjects across the Handguns, Marijuana, and Gambling Content Areas
Experimental Condition
Dependent Measure
Control
Inoculation Treatments:
Peripheral
Central
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HANDGUNS TOPIC
Attitude
Mean
SD
Threat
Mean
SD
Attitude
Mean
SD
Threat
Mean
SB
Attitude
Mean
SD
Threat
Mean
SD
5.08
(N=96)
2.17
417.
(#=150)
2.12
4.21.
(#=158)
2.08
4.05
(#=95)
2.10
4-73c
(#=149)
2.30
MARIJUANA TOPIC
4.78c
(#=157)
2.28
5.16
(#=100)
1.94
4.23,
(#=156*)
1.94
4.08.
(#=166)
2.03
3.82
(#=102)
1.98
4.13
(#=159)
2.13
GAMBLING TOPIC
4.35c
(#=167)
2.36
5.27
(#=95)
1.78
4.46,
(#=144)
1.86
4.74c
(#=158)
2.04
3
-73 b
(#=145)
1.84
3.81.
(#=157)
1.84
2.99
(#=96)
1.56
*'
Note: Ratings of respondent attitudes and threat were evaluated using 9-point scales. For the attitude measures,
the lower therating, the more resistant to the attack message. However, for threat, a higher rating is associated
with greater resistance.
, Significant compared to control at g < .001.
b Significant compared to control at g < .01.
c Significant compared to control at g < .05.
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Overall Findings
A series of 3 (systematic inoculation treatment, peripheral inoculation treatment,
and no inoculation/control) X 2 (lower and higher need for cognition) Multivariate
Analysis of Covariance (MANCOVA) tests, using Wilk's lambda test, were computed
on the dependent measures of attitude, responses to counterarguments, and receiver
threat across each of the three topics as the first step in examining the predictions and
research questions posited in this study. Ego-involvement was treated as a covariate
in the analyses. In addition, 3X2 ANCOVAs were computed on attitude change scores
on each of the three topics between Time 1 (which was prior to administration of
inoculative materials) and Time 2 (immediately following administration of
inoculative materials) and from Time 1 to Time 3 (from one to three weeks following
administration of persuasive attack). Significant omnibus effects were followed by
tests of simple effects, where needed, and subsequent assessment of means using
planned comparisons for all predicted effects and Scheffe post-hoc tests for all
nonpredicted effects.
To maintain clarity in the reporting of the findings of this study, omnibus results
are presented separately for each topic. Later, the relevant main and covariate effects
for specific variables are examined in the context of appropriate predictions. The
factorial MANCOVA indicated no interaction effects involving any of the three topics.
MANCOCA results for the handguns topic revealed main effects for experimental
condition, F(6,762) = 3.63, p < .01, R2 = .03, and nearly significant main effects on need
for cognition, F(3,381) = 2.59, p < .06, R2 = .02. The factorial ANCOVA on Time 1 to Time
3 attitude change for the handguns topic revealed a main effect for experimental
condition, F(2,388) = 3.35, p < .01, eta2 = .02.
The factorial MANCOVA results for marijuana indicated main effects for
experimental condition, F(6,820) = 4.39, p < .001, R2 = .03, and need for cognition,
F(3,410) = 2.79, p < .05, R2 = .02. The factorial ANCOVA on Time 1 to Time 3 attitude
change for marijuana indicated a main effect for experimental condition, F(2,402) =
5.56, p < .01, R2 = .02. The factorial MANCOVA for the gambling topic indicated a main
effect involving experimental condition, F(6,756) = 3.73, p < .01, R2 = .03, while the
ANCOVA on attitude change revealed a nearly significant main effect for
experimental condition, F(2,384) = 2.33, p < .10, eta2 = .01.
Hypotheses
Hypotheses 1 and 2 examined use of central and peripheral inoculation appeals in
conjunction with processing disposition. Hypothesis 1 posited that central inoculation
treatments are more effective than peripheral treatments. Uncontaminated main
effects for experimental condition across all three topic areas indicated that both
central and peripheral inoculation appeals confer resistance to influence, but failed to
reveal any statistically significant differences between the two approaches.
Subsequent planned comparison for handguns indicated that both central and
peripheral approaches instilled resistance on the dependent variable of attitude:
central, F(l,349) = 12.92, p < .001, eta2 = .04, and peripheral F(l,349) = 11.81, p < .001,
eta2 = .03.
The pattern of results was the same for the marijuana and gambling topics. With
both issues, central and peripheral appeals promoted resistance, but there were no
significant differences between approaches. Subsequent planned comparisons on
marijuana revealed main effects on attitude for central and peripheral approaches,
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F(l,383) = 15.44, p < .001, eta2 = .04, and F(l,383) = 20.82, p < .001, eta2 = .05, respectively.
Planned comparisons for gambling indicated main effects on attitude for central and
peripheral appeals, F(l,344) = 12.26, p < .001, eta2 = .04, and F(l,344) = 5.23, p < .05, eta2
= .02, respectively. This pattern of results suggests that central and peripheral
inoculation treatments are similar in their ability to promote resistance to subsequent
influence. These means are displayed in Table 1.
Hypothesis 2 predicted that inoculation is more effective in conferring resistance
among individuals who receive an inoculation treatment who are higher in need for
cognition. Omnibus MANCOVA results reported previously revealed significant
main effects on need for cognition with the handguns and marijuana topics. These
results were probed with one-way MANOVAs examining receiver need for cognition
among inoculated subjects. The pattern of means on need for cognition reveals that
those individuals higher in need for cognition were somewhat more resistant to
subsequent attacks, but mean differences attained statistical significance only with
the higher involving handguns issue, F(l,295) = 4.21, p < .05, eta2 = .02. With the
handguns topic, need for cognition triggered greater threat, F(l,295) = 5.10, p < .01, eta2
= .04, and, thus, more resistance to subsequent attacks. Need for cognition means on
attitude among inoculated subjects are displayed in Table 2. The results suggest
qualified support for Hypothesis 2.
TABLE 2
Attitude toward Attack Message Means among Inoculated Subjects Scoring Lower and Higher in Need for
Cognition across Handguns, Marijuana, and Gambling Content Areas
Dependent Measure
Need for Cognition
Lower
Higher
HANDGUNS TOPIC
Attitude
Mean
SD
4.46
(#=140)
2.03
3.94,
(#=164)
2.12
MARIJUANA TOPIC
Attitude
Mean
SD
4.29
(#=168)
1.96
3.99
(#=151)
2.03
GAMBLING TOPIC
Attitude
Mean
SD
4.54
(#=141)
1.87
4.69
(#=158)
2.04
Note: Ratings of respondent attitudes were evaluated using 9-point scales. The lower the rating, the more
resistant to the attack message.
m Significant at r¿< .05.
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Hypotheses 3,4, and 5 tested assimilation and contrast in the process of resistance.
Specifically, Hypothesis 3 predicted that inoculation immediately enhances existing
attitudes, while Hypothesis 4 posited that this tendency is most pronounced among
more ego-involved receivers. However, omnibus ANCOVAs computed on attitude
change scores from Time 1 (prior to inoculation) to Time 2 (immediately following
inoculation) revealed no statistically significant shifts in attitudes on the handguns,
marijuana, or gambling topics. It is clear that the inoculation process does not initially
strengthen existing attitudes.
Hypothesis 5 posited that inoculation subsequently instills resistance to
persuasive attacks. Results reported previously (see Table 1) indicate that inoculation
confers resistance to persuasive attacks. However, given the failure to confirm an
assimilation effect immediately following the administration of inoculative materials,
it would be inappropriate to describe the subsequent resistance provided as a contrast
effect.
However, the concept of ego-involvement is not restricted to use in social
judgment theory. As reasoned previously, more ego-involvement facilitates access to
relevant attitudes, thus increasing the likelihood that an individual can be induced to
perceive potential vulnerability of attitudes and be motivated to extend the cognitive
energy required to bolster attitudes. Thus, Hypothesis 6 posited that the tendency of
inoculation treatments to generate threat is most pronounced among more egoinvolved receivers, and Hypothesis 7 predicted that inoculation effects are more
pronounced among more highly ego-involved receivers.
To assess Hypothesis 6, the influence of ego-involvement was examined for the
main effect findings of experimental condition on the dependent variable of threat
across the three topics. The results indicated that the covariate of ego-involvement
attained statistical significance with the moderately involving marijuana topic, b = .34,
t = 7.41, p < .001, and low involving gambling topic, b = .19, t = 3.80, p < .001. The positive
betas indicate support for Hypothesis 6: the ability of inoculation treatments to
generate threat is most pronounced among more ego-involved receivers.
To evaluate Hypothesis 7, the influence of ego-involvement was examined for
main effect findings of experimental condition on the remaining dependent variables
across three topic areas. The pattern of results indicates no support for the prediction
that inoculation is more effective among more ego-involved receivers.
DISCUSSION
The results of this investigation enhance understanding of the process of
inoculation. The study used three controversial issues, representing low, moderate,
and high issue involvement and a roughly equal distribution of opinion for and against
each issue. The study addressed the potential of both central and peripheral
inoculation treatments to confer resistance to attack, adjusting for receiver need for
cognition, and explored the cognitive process triggered via inoculation.
Hypotheses 1 and 2 examined inoculation appeals and receiver message
processing disposition. Hypothesis 1 posited superiority of central as opposed to
peripheral appeals. The results offered no support for this prediction, instead
revealing that central and peripheral inoculation treatments are similar in ability to
instill resistance to subsequent influence.
This is the first test of central and peripheral message approaches in inoculation.
The finding that both approaches are equally effective adds to past evidence
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suggesting a robustness of inoculation appeals, whether they are fashioned as same
versus different (McGuire, 1961,1962,1966; McGuire & Papageorgis, 1961; Pfau, 1992;
Pfau & Burgoon, 1988; Pfau et al., 1990), or content versus source (Freedman & Sears,
1965; Stone, 1969).
One plausible explanation for this established pattern of null findings with regard
to inoculation message approach is that the threatening component in inoculation
overshadows refutational preemption in the process of resistance. Threat functions as
the motivational catalyst to inoculation. It is accomplished at the outset of the
inoculation treatment, followed by specific content for receivers to use to bolster
attitudes. Wyer (1974) previously speculated that warning people that their beliefs
may be attacked is sufficient to instill resistance to attacks. Wyer argued that
mentioning "arguments against a proposition may be sufficient to make the subject
aware of his vulnerability to attack and...may stimulate him to bolster—defenses"
(1974, p. 206).
This position is supported by the evidence indicating that inoculation confers
resistance to completely different arguments than raised in the inoculation treatment,
described previously, and by studies conducted by Freedman and Sears (1965) and
Kiesler and Kiesler (1964) which found that forewarning alone is enough to facilitate
resistance. In examining this thesis within the context of inoculation, McGuire and
Papageorgis (1962) reported that forewarning without refutational preemption is
sufficient to foster resistance, although the use of forewarning in combination with
refutational preemption is better. If the primary force of inoculation stems from the
threatening component of a treatment, then the contribution of the particular content
provided in the refutational preemption facet of the message will be minimized,
therefore reducing the likelihood that any structural or content differences in the
presentation of the refutational material will prove to be significant
Hypothesis 2 predicted that inoculation is more effective among receivers higher
in need for cognition. Results provided qualified support for this prediction,
indicating that greater need for cognition was associated with higher threat and, thus,
enhanced resistance, but only with the higher involving handguns issue.
The finding that receiver need for cognition influences the effectiveness of
inoculation is useful to practitioners who need to tailor treatments to target audiences.
The fact that greater need for cognition enhances the effectiveness of inoculation on
high involving, but not low involving, issues makes theoretical sense. Issue
involvement and receiver need for cognition both portend the presence of more
effortful message processing, which contributes to the overall effectiveness of
inoculation (Petty & Cacioppo, 1986; Pfau et al., 1997). Cognitive response research
suggests that messages enhance attitude persistence by motivating receivers to
generate their own thoughts about a topic (Cacioppo & Petty, 1989; Chaiken,
Liberman, & Eagly, 1989; Eagly & Chaiken, 1993; Petty & Cacioppo, 1986). Thus,
greater need for cognition should contribute to.the effectiveness of inoculation with
high involving issues.
The investigation focused on the cognitive process unleashed via inoculation.
The study posited the processes of assimilation and contrast, found in social judgment
theory (Sherif & Hovland, 1961; Sherif & Sherif, 1967; Shérif et al., 1965), as plausible
explanations for the cognitive process that inoculation triggers in receivers.
Hypotheses 3-5 addressed assimilation and contrast rationales, but the results of this
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study provided no support for an assimilation effect or for an interaction of
assimilation and ego-involvement Absent support for assimilation, it would be
inappropriate to interpret the pervasive main effect findings for inoculation across the
three topics as a contrast effect, as was reasoned in Hypothesis 5.
The results of this investigation suggest that assimilation and contrast do not offer
suitable explanations of the process of resistance. This finding confirms the reasoning
of Petty, Cacioppo, and Haugtvedt (1992) that assimilation and contrast are not good
process explanations for social judgment-like attitude movements. This study offered
a robust test of assimilation and contrast in inoculation. We therefore conclude that a
suitable rationale for the cognitive processes that are triggered via inoculation must lie
elsewhere (Pfau, 1997). Further theoretical and empirical work needs to be undertaken
to understand the nature of the internal processes set in motion by an inoculative
treatment.
Hypotheses 6 and 7 posited independent effects for the key term of egoinvolvement Results revealed support for Hypothesis 6, which predicted that the
capacity of inoculation treatments to generate threat is most evident in high egoinvolved receivers, at least for the moderately involving marijuana and low involving
gambling topics. The more ego-involved in a content area a person is, the more likely
he/she can access relevant attitudes (Fazio, 1989) thereby facilitating threat, which
requires that receivers perceive the potential vulnerability of attitudes. However, the
results provided no support for Hypothesis 7, which posited that inoculation effects
are most pronounced among more ego-involved receivers. Thus, greater egoinvolvement appears to contribute to the process of inoculation, enhancing threat, but
does not directly affect resistance.
Two caveats should be posited concerning the results of this study. First, the
investigation featured central and peripheral inoculation treatments, but it made no
attempt to manipulate or measure receiver message processing. As a result, the study
is unable to confirm whether the the treatments triggered central or peripheral
message processing in receivers. This shortcoming is compounded by the fact that,
according to the ELM, central and peripheral cues are determined on the basis of their
actual use (Petty & Cacioppo, 1986)
The second limitation of the results of this study concerns the small effect sizes
reported, which averaged .037 across all tests. In resistance research, however, small
effects sizes are common and meaningful. To detect inoculation effects, attack
messages administered to those receivers who support the opposing position must
exert influence. Clearly, even successful attacks will only account for a small
proportion of total variance in the attitudes of those committed to the opposing point
of view. Also, this study employed a single inoculation message per subject, but when
employed in the field, inoculation would be accomplished via multiple messages
delivered over time (Pfau et al., 1990; Pfau et al., 1992), thus enhancing their effect.
Eagly and Chaiken have called attention to the importance of even modest effect sizes,
particularly for research findings which carry potential field applications. "...[EJffects
that account for relatively small proportions of variance can still be consequential, and
often are regarded as extremely important in applied areas" (1993, p. 688).
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APPENDIX
Attack messages were prepared for and against each of the three topics and administered to
people opposing the position taken in the attack. Four inoculation messages were written for each
of the attack messages, two central and two peripheral treatments. To illustrate, the examples
included in the appendex feature an attack calling for legalization of marijuna, and four
inoculation messages designed to promote resistance to this attack.
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Attack Message
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IT'S TIME TO LEGALIZE THE SALE A N D USE OF MARIJUANA
Marijuana is a substance, and its use in the U. S. has become almost as common as that of other
substances, like alcohol. Recent government data indicates that more than one in every five
American teenagers and adults~37-million in all-have used marijuana. Given such extensive use,
the time has finally come to officially legalize the sale and use of marijuana in the U. S. This step
makes as much sense as the legalization of alcohol did more than 60 years ago. It would end the
hypocrisy associated with unenforceable laws. Further, it would result in a number of important
benefits!
One benefit is medical. Marijuana has important medical uses. It is used to treat cancer
chemotherapy patients. The prestigious Journal of the American Medical Association indicates
that 200,000 Americans are receiving chemotherapy treatments to combat cancer. Of these, more
than 50,000 experience severe nausea from treatments. Studies indicate that marijuana could
assist about half this group to overcome nausea. Marijuana can also be employed to treat
glaucoma, a serious eye disease. Mary Johnson, a glaucoma patient reports that, "Marijuana does
save my eyes, and my ophthalmologist says there is no other medicine to prevent me from going
blind." Finally, marijuana can be used to treat alcoholism. Tod Mikuriya, a prominent doctor,
recommends marijuana for his alcoholic patients. Research shows that regular marijuana use can
significantly lower consumption of alcohol.
In addition to its medical applications, the legalization of the sale and use of marijuana could
provide a financial bonanza, helping pay for needed public services, and reducing the national
debt. The amount spent on marijuana is staggering. One estimate indicates that approximately
$4 billion is spent annually on marijuana by users, and that more than 50 percent of this is profit
to the seller. One U. S. Senator estimates that legalization of marijuana would be accompanied
by a plan to tax its profits. He concluded that, "We could impose a tax similar to those on alcohol
and cigarettes, which would generate significant public revenues." Lisa Smith, a taxpayer,
observed the obvious. She said that, "If imposing a tax on marijuana could solve government's
financial problems, and as a result improve our living standard, why not do it?"
Since legalizing marijuana could bring so many benefits, why not do it? Just as government
legalized alcohol more than 60 years ago, the time has come to legalize the sale and use of
marijuana. It just makes sense!
Inoculation: Refutational Same, Central
D O N T LEGALIZE THE SALE AND USE OF MARIJUANA
Marijuana is a harmful drug that should remain illegal. Despite this fact, there is a new
campaign underway to legalize the sale and use of marijuana in the U. S. Some of the appeals of
this campaign are so persuasive that they may cause you to question your opposition to
legalization.
Advocates for the legalization of marijuana claim the substance provides important medical
benefits for people, especially for cancer patients who suffer from nausea following chemotherapy
treatments. However, many studies show that marijuana provides only short-term antiemetic
relief, and only for a minority of users. Instead of relief, more than 70% of the people studied
experienced side effects, but received no benefits. Besides, for patients who would benefit
medically, existing laws permit physicians to prescribe marijuana.
Proponents of legalization also claim that this step can provide an important new source of
government tax revenue, much like those derived from the sale of cigarettes and alcohol. But, this
Nuances in Inoculation
479
advantage would be more than offset by the social costs of legalization. At the most, a tax would
raise about $2-billion annually, according to those who advocate legalization. However, one
recent health report placed the social pricetag of marijuana use at $10.3-billion per year, several
times the social costs of cigarettes or alcohol. If the legalization of marijuana increases its use,
which many studies maintain, the human cost would be tragic.
Remember that marijuana is a harmful drug. Oppose efforts to legalize the sale and use of
marijuana in the U. S.
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Inoculation: Refutational Different, Central
DONT LEGALIZE THE SALE AND USE OF MARIJUANA
Marijuana is a harmful drug that should remain illegal. Despite this fact, there is a new
campaign underway to legalize the sale and use of marijuana in the U. S. Some of the appeals of
this campaign are so persuasive that they may cause you to question your opposition to
legalization.
Those who support the legalization of marijuana maintain that it would benefit America.
What they ignore is the personal and economic devastation it would cause.
On a personal level, marijuana use places the individual at risk. Marijuana use speeds
heartbeat. One study found that use increases heartbeat significantly, in some cases to twice its
normal levels. In economic terms, marijuana use costs the U. S. economy billions in lost revenues.
Research indicates that drug use in the work place is widespread, and that marijuana use is the
primary culprit. It slows motor response, and thus places workers at risk. Studies show that
accidents involving machinery, including motor vehicles, are the main cause of death and injury
in the work place, and that most of these are drug-related. Marijuana use also undermines worker
productivity. A survey of 3,000 General Motors workers in 13 plants throughout the U. S. revealed
that drug-dependent employees visited company medical clinics 15 times more often, and
experienced more than twice as many occupational injuries, resulting in 25 more lost working
days each year in disability leave. Remember that marijuana is a harmful drug. Oppose efforts
to legalize the sale and use of marijuana in the U. S.
Inoculation: Refutational Same, Peripheral
DONT LEGALIZE THE SALE AND USE OF MARIJUANA
Marijuana is a harmful drug that should remain illegal. Despite this fact, there is a new
campaign underway to legalize the sale and use of marijuana in the U. S. Some of the appeals of
this campaign are so persuasive that they may cause you to question' your opposition to
legalization.
Advocates for the legalization of marijuana claim that the drug provides important medical
benefits for people, especially for cancer patients who suffer from nausea following chemotherapy
therapy. But, according to prominent oncologist Dr. James Moertel, marijuana offers only shortterm antiemetic relief, and only for a small minority of patients. George Kagen, a cancer patient
who used marijuana during his chemotherapy, adds that, "In my experience, the benefits of
marijuana use, when they do occur, are immediately followed by side effects." Besides, for those
patients who need to use marijuana for medical purposes, existing laws permit physicians to
prescribe it.
Proponents of legalization also claim that this step would provide an important new source
of government tax revenue, much like those derived from cigarettes and alcohol. However, this
advantage would be more than offset by the social cost of legalization. Jack Stiff, an expert on
480
Pfau, Tusing, Lee, Godbold, Koerner, Penaloza, Hong, and Yang
adolescent problems, advises that, "The damage of marijuana to users, particularly adolescents,
is unimaginable." Or, as Lulu Loughlin, the mother of a marijuana user, put it: "If I lose my son,
nothing can repay that loss."
Remember that marijuana is a harmful drug. Oppose efforts to legalize the sale and use of
marijuana in the U. S.
Downloaded by [University of Minnesota Libraries, Twin Cities] at 15:40 23 October 2012
Inoculation: Refutational Different, Peripheral
DONT LEGALIZE THE SALE AND USE OF MARIJUANA
Marijuana is a harmful drug that should remain illegal. Despite this fact, there is a new
campaign underway to legalize the sale and use of marijuana in the U. S. Some of the appeals of
this campaign are so persuasive that they may cause you to question your opposition to
legalization.
Those who support legalization of marijuana say it would benefit America. What they ignore
is the personal and economic devastation it would cause. On a personal level, marijuana use places
the individual at risk. Dr. Adam Sulkowski explains that marijuana use increases heart rate
significantly, in some cases to twice its normal levels. In economic terms, marijuana use costs the
economy billions in lost income.'Newsweekreports that drug use in the work place is widespread,
and that marijuana use is the primary culprit. It slows motor response, thus placing workers at
risk. William Taft, president of the Manufacturers' Association of Southern Connecticut, explains:
"Marijuana slows reactions and therefore can cause accidents. An worker who is hurt is no longer
able to participate in production." Former drug user John Carpenter explains, "I lost my fingers
in an accident due to drug use, and I lost my job." Marijuana use also reduces worker productivity.
Dr. Robert Carlton warns that, "If we don't wake up and address the disastrous and wide-ranging
effects of drug use in the workplace, the U. S. is doomed to become a second-rate power."
Remember that marijuana is a harmful drug. Oppose efforts to legalize the sale and use of
marijuana in the U. S
Nuances in Inoculation
481