Summary of:
Kurzban, R. & Leary, M.R. (2001). Evolutionary origins of stigmatization: The functions of
social exclusion. Psychological Bulletin, 2, 187-208.
Summary by Lauren Frazier, Chris Kelleher, and Jessica Williams
For Dr. Mills’ Psyc 452 class, Spring, 2012
Social contact is important for maintaining one’s behavioral and emotional health.
Through a process called stigmatization, certain individuals are excluded from some social
interactions because of a particular characteristic they may possess. Examples of people that may
be excluded are those suffering from disease, the obese, and the homosexuals. The focus of this
article is to discuss stigmatization and question why a social species would reject its own
members. A stigma may come about when a person’s social attributes do not meet the norm of
society. There is an evolutionary approach presented in this article dealing with stigmas. It
suggests that there are “distinct, domain-specific psychological mechanisms that have evolved to
solve adaptive problems associated with sociality.” People are stigmatized if they possess a
quality viewed by society as a basis for exclusion. According to the literature review, people may
stigmatize others to enhance things such as self-esteem and social identity or to justify certain
social and economic structures.
Social exclusion has been recorded in both human and nonhuman species. In animals,
territoriality (excluding other animals from a specific area) is social exclusion. Doing this
prevents those animals from taking advantage of resources such as food and mating areas.
Another example is when animals create status hierarchies. Organisms at the top may impose
certain restrictions on those at the bottom. These nonhuman examples may illustrate the
possibility that the human psychology of social exclusion might have been created due to the
similar environmental pressures of other species.
There are advantages and disadvantages to living in a social group. Advantages are things
such as parental investment, mating, and mutual cooperation to achieve goals. Disadvantages are
conflict, violence, competition for resources, disease, etc. “It has been suggested that humans
have specific adaptations for kin-directed altruism or social exchange, reciprocal altruism or
social exchange and within-group cooperation.” The authors argue that stigma arises from dyadic
cooperation (avoid interactions that yield poor social exchange), coalitional exploitation (exclude
individuals from the benefits of their group), and parasite avoidance (prevent contact with those
with disease). The paths of reciprocal altruism and mutual engagement may have led to
adaptations that cause humans to seek out good social exchange partners and stigmatize others.
Stigmatization may occur if someone has unpredictable goals and behavior, a history of cheating,
and little social or economic resources. Coalitional exploitation persuades individuals to belong
to groups and also to exploit members of other social groups. When coalitional psychology is
engaged, in-group favoritism and intergroup competitiveness is expected. Cues such as clothing,
skin color, and speech patterns can trigger coalitional psychology. These cues must be learned
through social experience. Parasite avoidance is designed to avoid those with detrimental
pathogens. Emotions are evoked from these three stigmatizing conditions. Dyadic elicits anger,
coalition evokes fear and hate, and parasite avoidance evokes disgust. The proposal from these
authors suggests that the systems that underpin stigmatization are designed to solve particular
adaptive problems.
Outline: Evolutionary Origins of Stigmatization: The Functions of Social Exclusion
1. Current literature on the functions of stigmatization and social exclusion
a. Most of the literature suggests that people stigmatize others to:
i. Enhance their self-esteem
1. Discrimination enhances self-esteem
2. Threatened self-esteem motivates discrimination
3. Researchers have failed to find evidence for either of these
corollaries
ii. Enhance their social identity
1. This has been rejected in many studies because it does not explain
why some members of certain groups are stigmatized, while others
are not
2. People have a broad array of individuals and groups from which to
derive their own identity and self-esteem
iii. Justify a particular social, economic, or political structure
1. People make attributions about:
a. Deservingness
b. Positive and negative traits
c. Worthiness of members of different groups based on
current social structure
2. Examples from nonhuman animals to give a sense of selection pressures that might lead
to adaptations for social exclusion
a. Territoriality is an expression of social expression, likely to exist so that
organisms can monopolize resources such as food and mating sites
b. The establishment of status hierarchies, where the individuals at the bottom of a
hierarchy are socially excluded in a way that parallels the phenomenon in humans
c. Social ostracism has also been found amongst nonhuman species, especially
among animals like 3 spined sticklebacks, lemurs, baboons,
d. Intergroup competition amongst species suggest a strong psychology of
discriminate sociality, which lies at the heart of stigma
3. Human adaptations for sociality include cognitive mechanisms that cause people to be
selective in their social interactions
a. Decreasing the probability of being cheated in a social exchange and avoiding
interactions with partners who have little to offer in terms of social gain
b. Maintaining one’s group integrity and exploiting those in subordinate groups
c. Decreasing the probability of parasitic infection
4. Predictions of the model and some suggested future empirical work
a. Additional measures of social distancing are required to fully assess the
multifaceted nature of stigmatization
b. Elicit preferences for the kinds of interactions that people prefer to avoid
c. Investigate a breadth of stigmatizing conditions so that differences and similarities
in the reactions they evoke can be clarified and systemized
Critical Review Items:
a) Interesting Points
 We found the section explaining the nonhuman evidence of social exclusion to be rather
interesting. The examples provided, such as territoriality, status hierarchies, and social
ostracism illustrate that discriminate sociality is present in many species. It is believed
that the human psychology of social exclusion might have been molded by the selection
pressures, similar to those that led to the adaptations of the nonhuman behaviors

We found it interesting, as well as agree with the researchers as they critique the theories
that suggest that people stigmatize others based on social identity. The researchers point
out that maintaining social identity does not easily explain why members of certain
groups are stigmatized whereas others are not. Although self-esteem and stigma are
connected in some way, there is still no satisfying account of why individuals
discriminate against particular others.
b) Unclear Points
 The article speaks about exploitation as a form of stigmatization. We disagree with this
point because we think we that in evolutionary times it would be very costly to use
energy to exploit others. We don’t understand why our ancestors would use this energy to
exploit others if they had not been exploited first.
Test Questions:
1. According to the reading, territoriality is an expression of social exclusion. (T/F)
2. The less visible a stigmatizing condition, the greater its (negative) impact on interactions.
(T/F)
3. Nonhuman organisms, such as fish, have been known to exclude other members of their
own species who are infested with parasites. (T/F)
4. According to the reading, there are: a) only costs to living in groups, b) only benefits to
living in groups, or C) both costs and benefits to living in groups.
5. Stigmatization is: a) genetically endowed, b) only expended by “racists”, c) learned
through sociality.
6. In general, according to this article, stigmas are, a) a way to separate good people from
bad, b) a processed of exclusion of particular individuals from certain types of social
interactions c) not evolutionarily explainable.
Answer Key:
1. True
2. False
3. True
4. C
5. C
6. B