Stewart-Williams, S. (2007) Altruism among kin vs. nonkin: effects of cost of help and reciprocal
exchange. Evolution and Human Behavior, 28, 193-198.
Summary by Elaine Rehm, Ebonie Buenrostro, Mika Galiher; PSYC 452 Dr. Mills, Fall 2014.
In the article, “Altruism among kin vs. nonkin: effects of cost of help and reciprocal exchange”
by Steve Stewart Williams the dimensions of altruism among kin and non kin are explored. Williams
goes on to define the specifics of human altruism and their relationship with Hamilton’s kin selection
theory (KST), which is unable to explain today’s current findings on human altruism. William’s sought
to reconcile Hamilton’s study by looking at the cost of helping and levels of reciprocal exchange.
Williams suggests that while individuals continue to help nonkin despite the security of reciprocity there
are various outlets to which benefits can occur. His first hypothesis is “As the cost of helping increases
the share of help given to kin will increase, and the share given to non kin will decrease” (Williams,
2007). Current findings suggest that kin show less reciprocity than nonkin because the indirect benefits
of helping a kin outweigh the costs of unreciprocated help therefore Williams makes his second
hypothesis, “The association between help given and help received will be larger for acquaintances than
for friends and larger for friends than for siblings” (Williams, 2007).
The study used 295 undergraduate psychology students: 146 males and 149 females, ages ranged
between 16 and 46 (mean =18.71; S.D. =2.58). Participants were recruited online from a pool of
undergraduate psychology students who received credit for participation. The participants completed the
following questionnaires. Finding Person A began with answering questions about one member of their
social network (Person A). The conditions of the individual were then defined by 8 states including sex
and relationship. Participants then completed a word-meaning test meant to prime them in order to
increase accuracy of their self-report surveys. The final questionnaire focused on the participants’
assigned individual from the previous section to gather demographic and altruistic information. Altruism
was defined and analyzed through the break down into the following categories of help: low, medium
and high cost help based on certain responses to questions.
Results were converted to t-scores to compare the low, medium and high cost help given to
members of each relationship category through an ANOVA test. The results revealed an interaction
between relationship category and cost of help given. Between group analyses were further analyzed in
the low, medium and high cost help groups. As the cost of help rose the relative ranking of friends fell.
Testing hypothesis one through within group analyses concluded that siblings received a larger share of
medium cost help than they had of low cost help and larger high cost help than medium cost help.
Acquaintances received a smaller share of medium than low cost help and friends received a smaller
share of medium than low cost help. Linear regressions were computed to test hypothesis two with
newly formed aggregate variables with all B values being significant. Results with a 95% confidence
interval suggested consistent with hypothesis two that the degree of reciprocity among acquaintances
was significantly higher among friends than siblings.
Findings are consistent with past research suggesting that for siblings, cousins and acquaintances
greater reciprocity was associated with higher levels of altruism (Williams, 2007). The study clarifies
that the level of help within each relationship was dependent on the cost of help where as the cost
increased the share of help to kin increased and nonkin decreased. Participants were more likely to help
in high cost situation for kin than nonkin possibly due to emotional closeness. The findings of
acquaintances exhibiting a higher level of reciprocity than siblings or cousins compared to friends were
due to the wider temporal window in friendly relationships. The findings are consistent with the idea that
friendship works in terms of RAT as well as the generational pull of altruism functioning within
generations not between where siblings and cousins engage in reciprocal altruism more so than parent
and offspring due to the close relation in age and experiences.
Outline: Stewart-Williams, S. (2007) Altruism among kin vs. nonkin: effects of cost of help and
reciprocal exchange.
I.
II.
III.
Introduction
a. Hamilton’s (1964) kin selection theory (KST) – the closer the relation, the higher the
level of altruism
i. However, there are some exceptions
ii. High cost of helping, more common with genetic relatives – more direct cost to
fitness
b. Hypothesis 1: “As the cost of helping increases, the share of help given to kin will
increase, and the share given to nonkin will decrease.”
c. Tivers’ (1971) reciprocal altruism theory (RAT) – altruism can increase fitness when
there is a high chance of reciprocity by the other person (i.e. acquaintance or friend)
i. Reciprocation is important among nonkin, but not among kin
d. Hypothesis 2: “The association between help given and help received will be larger for
acquaintances than for friends, and larger for friends than for siblings or cousins.”
Method
a. Participants
i. 295 undergraduates, 146 male, 149 female
b. 8 conditions based on gender & relation to participant
i. All ages were approximately the same
ii. Relations = Full siblings, half-siblings, cousins, aunts, uncles (divided into first
and second degree kin); acquaintances; close friends
iii. Gender = male/female
c. Participants asked about level of helped received & given in the last 2 months – in the
low cost and medium cost categories
d. Participants asked about level of help willing to give for low, medium or high cost
situations
i. Low = emotional support
ii. Medium = help during an illness, help during a crisis, help with everyday living,
help with housing and financial help
iii. High = willingness to donate a kidney, willingness to risk injury or death
providing help during a life-saving emergency
1. Used Likert-type scale 1 to 9
2. Considered also residential proximity, likely contact within the year,
frequency and duration of contacts
Results
a. The amount of help given was related to the relationship category and the cost of the help
b. For siblings, cousins and acquaintances: Greater relatedness – higher rates of helping
i. Friends were the exception, until the cost of help rose
c. Comparison of amount of help in terms of cost
i. Siblings proved both hypothesis – although high vs. medium was not significant
ii. Cousins – mixed support
iii. Acquaintances – received also smaller shares
iv. Friends – received a smaller amount of medium vs. low
d. Kinship and reciprocity
i. Low cost = friends more than siblings
ii. Medium = siblings and friends equal
IV.
V.
iii. High = Siblings over friends
e. Reciprocity higher in acquaintances than friends
f. Higher reciprocity than expected among kin & reciprocity among friends, not higher than
siblings (against hypothesis 2)
Discussion
a. Siblings, cousins and acquaintances
i. Greater relatedness = higher levels of altruism
ii. Confirms prior research
iii. Consistent with evolutionary psychology principles
b. Level of help dependent on cost of help
c. Level of help also dependent on relationship
i. “Proposed that emotional closeness is an evolved psychological disposition that
helps to mediate the link between relatedness and altruism.”
ii. This study shows how the amount of help is dependent on help received and
relationship categories
iii. Problem of hypothetical helping
Conclusion
a. Consistent with inclusive fitness theory
Test Questions
True or False
1. Willing to die to save a relative such as saving a sibling is best known as altruistic suicide?
2. Population growth depends on when and how many children and individual bears?
3. Perceptions of a child’s resemblance to their father do not affect his degree of investment and the
magnitude of the cost he inflicts on his spouse?
4. Parent-Offspring conflict starts in the mother’s womb?
Multiple Choice Questions
1. Population growth is controlled by which of the following?
A. Famine
B. Plague
C. War
D. Birth control
E. All of the above
2. Which of the following is a theoretical implication of Hamilton’s rule?
A. Grandparents and Grandchildren
B. Hypotheses about universal aspects of kinship
C. Friend Relationships
D. Both A & B
3. Which of the following are NOT considered “Dark Sides” of families?
A. Sibling Conflict
B. Friend Conflict
C. Parent-offspring conflict
D. Parent Conflict
Answer Key
True/False
1. True
2. True
3. False
4. True
Multiple Choice Questions
1. E. All of the Above
2. D. Both A & B
3. B. Friend Conflict