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Timothy Ketelaar
Signals and Sentiments: Exploring the role of
Emotions
in Adaptive Decision-making
I’m a social-cognitive scientist who adopts an
interdisciplinary perspective that combines evolutionary
psychology, experimental economics, and game theory to explore
the role of emotion in judgment and decision-making.
Historically, evolutionary perspectives on emotion have
focused on two broad perspectives: 1) Emotions-as-Sentiments and
2) Emotions-as-Signals (Bowlby, 1969). My research embraces both
views by exploring the idea that emotions are “designed” as
cognitive systems for generating “affective information” (Schwarz
& Clore, 1983; Ketelaar & Clore, 1997). Rather than simply
demonstrating that emotions can influence decision-making in very
peculiar ways (something we already know), my research focuses
instead on the question of whether emotions are “designed” to
provide affective information that serves to aid, rather than
impair, personal and social decision-making (Ketelaar & Au, 2003;
Ketelaar & Clore, 1997; Ketelaar & Todd, 2001).
The central assumption of my research is that emotions
provide “affective information” –in the form of sentiments or
signals -- which can influence decision-making by virtue of
altering the payoffs/utilities that individuals assign to
outcomes. For example, if a particular food evokes the emotion
of disgust, this would be equivalent to assigning a large
negative payoff (disutility) to the prospect of eating that
particular food item. As such, it would be reasonable to expect
that a person’s food choices would reflect this affective
influence (emotions-as-sentiments). Similarly, if a person feels
guilty after engaging in a specific social behavior, this would
be the equivalent of assigning a large negative payoff to that
particular behavior, and it would be reasonable to expect that
this person would be less inclined to pursue that behavior in the
future. Emotional displays, on the other hand, can also
influence decisions by virtue of providing individuals with
insights into how the signaler represents payoffs (emotions-assignals). For instance, if you observe that a person is
displaying anger in reaction to your behavior, you might utilize
this information to infer that they have assigned a large
negative payoff to your behavior and that they will be motivated
to prevent you from acting in this manner in the future.
By
contrast with previous approaches to emotion, my research aims to
determine whether these affective influences on decision-making
reveal evidence of adaptive design.
Emotions as Sentiments
Theorists from Adam Smith (1759) to Robert Trivers (1971)
and more recently economists Jack Hirschliefer (1987) and Robert
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Frank (1988), have argued for a version of the “emotions-assentiments” view in which emotional feeling states are viewed as
a plausible mechanism for sustaining subjective commitments to
strategies that run counter to one’s immediate material selfinterest. Frank (1988, p. 53), for example, has argued that
emotions:
“can and do compete with feelings that spring from rational
calculations about material payoffs….
Consider, for example, a person capable of strong
guilt feelings. This person will not cheat even when
it is in her material interests to do so. The reason
is not that she fears getting caught but that she
simply does not want to cheat. Her aversion to
feelings of guilt effectively alters the payoffs she
faces.”
For over one decade this view of emotional sentiments has been so
compelling that it has been accepted at face value without being
subject to empirical test. In this regard I have recently
utilized several social bargaining games familiar to Experimental
Economists to provide the first direct empirical test of this
emotions-as-sentiments view (Ketelaar & Au, 2003).
While my empirical findings are generally consistent with
Frank’s (1988) proposal that certain emotions, such as guilt, can
compel cooperation in social bargaining games, my research also
suggests an important caveat to the emotions-as-sentiments
perspective. Specifically, we have observed rather striking
individual differences in the tendency to experience feelings of
91.7 differences
%
guilt, and these individual
translate into rather large
differences in strategic behavior (see Figure 1).
Percentage
of
Generous
offers
in Round
Two
100
80
60
22.2 %
40
20
0
Felt
“Guilty”
(n= 12)
NO
“Guilt”
Feelings
9) Offers in an Ultimatum
Figure 1. Percentage of generous (> (n=
$10)
game as a function
of whether the individual did felt Guilty or did not
feel guilty about making
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a selfish offer in the first round of play (Ketelaar &
Au, 2003).
For example, in a repeated Ultimatum game, individual differences
in the propensity to feel guilty after proposing an unfair offer
had a profound impact on the magnitude of the monetary offers
observed in the second round of play. Moreover, a second study
revealed similar individual differences in a repeated Prisoner’s
Dilemma game, where it was observed that individuals who felt
guilty displayed 25% more cooperation compared to those who felt
no guilt (see Ketelaar & Au, 2003).
Although Adam Smith (1759) explained individual differences
in the capacity to experience moral sentiments in terms of a
failure to exercise “self-command,” I have utilized evolutionary
game theory to explore another, more intriguing possibility,
namely that individual differences in the capacity to experience
social-moral emotions represent a frequency-dependent
distribution of emotion-based strategy types akin to what social
dilemma researchers have called Social Motives (van Lange, et
al., 1997, Ketelaar, 2004a, 2004b). What is unique about my
approach is that I combine empirical findings from my own
experimental economics studies on emotional decision making with
theoretical concepts from evolutionary game theory (frequency
dependent selection, evolutionary stable strategies, the folk
theorem) into a model of how individual differences in emotions
might correspond to several distinct emotion-based commitment
strategies (Ketelaar, 2004a, 2004b). Specifically, I have argued
that individual differences in the capacity to experience moral
sentiments can give rise to a meta-stable population structure
comprised of approximately 40% prosocial strategists, 25%
individualists, 10% competitive strategists, and a very small
(<5%) proportion of ruthlessly non-cooperative strategists
(Ketelaar, 2004a, 2004b, see also Lomborg, 1996). In this manner
I have been able to expand the “emotions-as-sentiments” view into
an empirically-tested and theoretically-grounded model of
emotional influences on adaptive decision-making.
Emotions as Signals
The view that emotions are sentiments assumes that emotions
operate as strategic mental states that alter perceptions of the
subjective utilities assigned to particular courses of action
(Tooby & Cosmides, 1990; Ketelaar & Todd, 2001). The view that
emotions are signals, on the other hand, assumes that emotions
can also operate as mechanisms for conveying threats and promises
capable of supporting contracts and norms (Hirschleifer, 1987,
2001; Frank, 1988; Nesse, 2001). I believe that both of these
views of emotions (signals and sentiments) are related (see
below).
In a recent series of cross cultural studies, I have found
that there is a high degree of agreement across cultures in regard
to which emotional signals are likely to be displayed in various
social bargaining games such as the Prisoner’s Dilemma and the
Coordination game (Ketelaar, Au, Hu, Tomala, and Steiner, in
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prep.). Figure 2 shows that “contempt” as well as “anger” and
“disgust,” are associated with the so-called “Sucker’s Payoff” in
the Prisoner’s Dilemma game. These results are important because
they expand the range of emotions studied by decision-researchers
beyond the list of usual suspects such as happiness, sadness, and
anger. Moreover, recent research has also shown that these same
three social moral
Figure 2. Percentage of each “culture” indicating that they
would display particular
emotions (see right side of figure) if they found
themselves in the so-called
“Sucker’s Payoff” outcome in the Prisoner’s
Dilemma game.
emotions—Contempt, Anger, and Disgust—are evoked in relation to
violations of three different types of rights (see Rozin, et
al., 1999). I have recently replicated Rozin’s (1999) findings
in two locations in China and one in Ecuador, where we find that
anger displays are associated with violations of personal rights
(autonomy), contempt is associated with violations of social
duty (community rights) and disgust is associated with
violations of social norms concerning purity (divinity).
In an effort to discover how these emotion signals might
relate to strategic behavior, I have extended these findings into
the domain of experimental economics, where I have observed two
interesting findings: First, it appears that individuals
routinely utilize facial displays of emotion to infer stable
social motives rather than fleeting mental states (Ketelaar,
Tost, Davis, & Russell, in prep.). That is, rather than simply
attributing mental states to muscle movements (e.g., he is sad
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because he moved his frown muscles), participants in two
experiments were observed to attribute stable, trait-like, social
motives to the individuals who displayed particular emotions
(e.g., he is angry, thus he must be an uncooperative and selfish
person). Second, we have found preliminary evidence to suggest
that these emotional signals are predictive of actual behavior in
social bargaining games. The idea is not that putting on an
angry face makes you less cooperative, but rather that only less
cooperative people display anger (in certain contexts). The key,
of course, is to identify those contexts in which the presence or
absence of a particular facial display will be indicative of
stable social motives and actual behavior.
One such context that we have discovered involves the
presence or absence of an embarrassment display after receiving a
compliment (Ketelaar, Russell, & Davis, in prep.). Much of this
work borrows from the work of evolutionary anthropologists who
have shown that hunter-gatherers who reject compliments after a
successful foraging trip are often observed to distribute their
bounty equally amongst their group; whereas in other contexts in
which these compliments are not rejected, resources are
distributed in a more nepotistic manner (primarily to kin).
Consistent with what is found in hunter-gather studies we have
observed that undergraduates who display embarrassment when
complimented are more likely to give a larger portion of their
$11 endowment to their partner in a Dictator game (see Figure 3).
Displays Embarrassment
Happiness
(smile, gaze aversion)
smile)
KEPT $5, GAVE $6 to her partner
to her partner
Displays
(felt
KEPT $7, GAVE $4
Figure 3. Typical emotional reactions to compliments associated
with generous and
non-generous distributions of resources in a
Dictator Game (Ketelaar, Russell, & Davis, in prep.).
References
Bowlby, J. (1969). Attachment and Loss, Volume I.
Frank, R. H. (1988). Passions with reason: The strategic
role of the emotions. New York: W. W. Norton.
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Hirshleifer, J. (1987.) “On the Emotions as Guarantors of
Threats and Promises”, in J. Dupré, ed., The Latest on the Best:
Essays on Evolution and Optimality, Boston: Bradford Books-MIT
Press, pp. 307-326
Ketelaar, T. (2004a, in press) Signals and Sentiments:
Using Evolutionary insights to explore the role of Emotion in
Experimental Economics. Invited Chapter to appear in Zeelenberg,
M., Murnighan, K. & DeCremer, D. (Eds). Social Psychology and
Economics.
Ketelaar, T. (2004b). Ancestral Emotions, Current Decisions:
Using Evolutionary Game Theory to explore the role of Emotions in
decision-making.
In Crawford, C. & Salmon, C. (Eds).
Evolutionary Psychology, Public Policy and Personal Decisions,
(pp. 145-163). Lawrence Erlbaum Associates.
Ketelaar, T. & Au, W. T.
(2003).
The effects of guilty
feelings on the behavior of uncooperative individuals in repeated
social bargaining games: An Affect-as-information interpretation
of the role of emotion in social interaction.
Cognition &
Emotion, 17, 429-453.
Ketelaar, T., Au, W.T., Hu, W.P., Tomala, M. & Steiner, R.
(in prep) Emotional Signaling in Social Dilemmas: Cross-Cultural
evidence from the Prisoner’s Dilemma and Coordination Game.
Ketelaar, T. & Clore, G. L. (1997). Emotions and reason:
The proximate effects and ultimate functions of emotions. In G.
Matthews, (Ed.) Personality, Emotion, and Cognitive Science, (pp.
355-396). Advances in Psychology Series, Amsterdam: Elsevier
Science Publishers (North-Holland).
Ketelaar, Russell, D. & Davis, M. (in prep.). Contempt and
Compliments: Individuals who signal Contempt and Embarrassment
are more generous in distributing foraged resources.
Ketelaar, T. & Todd, P. M. (2001). Framing our thoughts:
Ecological rationality as evolutionary psychology's answer to the
frame problem.
In Holcomb III, H. R. (Eds.) Conceptual
Challenges in Evolutionary Psychology: Innovative Research
Strategies, (pp. 179-211). Kluwer Publishers.
Ketelaar, T., Tost, J., Davis, M. & Russell, D. C. (in prep)
Motives and Muscles: Trait attributions from Emotional Facial
Expressions.
Lomborg, B. (1996). Nucleus and shield: The evolution of
social structure in the iterated Prisoner’s Dilemma. American
Sociological Review, 61, 278-307,
Nesse, R. M.. (2001). Evolution and the Capacity for
Commitment. New York: Russell Sage Foundation.
Schwarz, N., & Clore, G. L. (1983). Mood, misattribution, and
judgments of well-being: Informative and directive functions of
affective states. Journal of Personality and Social Psychology,
45, 513-523.
Van Lange, P. A.M., Otten, W., DeBruin, E.M.N., & Joireman, J.A.
(1997). Development of prosocial, individualistic, and competitive
orientations: Theory and preliminary evidence. Journal of
Personality and Social Psychology, 73, 733-746.
Tooby, J. & Cosmides, L. 1990. “The Past explains the
Present: Emotional Adaptations and the Structure of Ancestral
Environments”, Ethology and Sociobiology, 11, 375-424.
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