Altruism among Kin vs.
NonKin: Effects of Cost of
Help and Reciprocal Exchange
BY NOELLE BRINGMANN, AUTUMN NAILES,
MELANIE SIMMS & MEGAN WILSON
Stewart-Williams, S. (2007). Altruism Among Kin vs. Non-kin: Effects of Cost of Help and Reciprocal
Exchange. Evolution and Human Behavior, 28(3), 193-198.
Levels of Altruism
 Kin Altruism- we are more likely to help those we are
genetically related too
 But what about friends?
 Explained by Reciprocal Altruism- the tendency to
help non-kin based on a likelihood of return


More likely to accept extended periods of timeframe for return
on investment- Lessening the importance of Reciprocal
Altruism
The need for Reciprocal Altruism becomes stronger between
acquaintances
Stewart-Williams, S. (2007). Altruism Among Kin vs. Non-kin: Effects of Cost of Help and Reciprocal
Exchange. Evolution and Human Behavior, 28(3), 193-198.
Hypothesis
 1- As the cost of helping increase, the share of help
given to kin will increase and the share given to
nonkin will decrease
 2- The association between help given and help
received will be larger for acquaintances than for
friends, but larger for friends than cousins or siblings
 Assets likelihood of



low-cost: emotional support
Medium-cost: helping during crisis, illness, everyday living
High-cost: giving a kidney
Stewart-Williams,S. (2007). Altruism Among Kin vs. Non-kin: Effects of Cost of Help and Reciprocal
Exchange. Evolution and Human Behavior, 28(3), 193-198.
Results- Altruism
 Siblings
 Low > Med > High
 Acquaintances
 High> Med> Low
 Friends
 Most help in Low- Cost
 Med equal with siblings
 High equal with cousins
60
Help Given (t-scores)
 Cousins
 Low> Med
Help Given as a function of Relationship
Category and Cost of Helping
55
50
Low-Cost Help
45
Medium-Cost
Help
40
35
30
Relationship Category
Stewart-Williams,S. (2007). Altruism Among Kin vs. Non-kin: Effects of Cost of Help and Reciprocal
Exchange. Evolution and Human Behavior, 28(3), 193-198.
Results- Reciprocity
 Higher among acquaintances then
friends/siblings/cousins
 Not higher among friends then cousins or siblings

Contrary to Hypothesis 2
Stewart-Williams,S. (2007). Altruism Among Kin vs. Non-kin: Effects of Cost of Help and Reciprocal
Exchange. Evolution and Human Behavior, 28(3), 193-198.
Critical Review
 Friends received a comparable amount of help to kin.
 Although young adults state that they are
emotionally closer to their friends than their siblings,
they were more willing to give high-cost help to their
siblings than they were to give to their friends.
 A high level of reciprocity was found among kin,
especially among siblings.
Stewart-Williams,S. (2007). Altruism Among Kin vs. Non-kin: Effects of Cost of Help and Reciprocal
Exchange. Evolution and Human Behavior, 28(3), 193-198.
Critical Review
 The high cost item that assessed whether or not the
participant would be willing to give a kidney.
 The study compared actual helping to hypothetical
helping.
 The cost of help could be a result of cultural norms
and not a result of kin selection theory or reciprocal
altruism theory.
Video
 http://www.youtube.com/watch?v=WNJz-T5R9FA
Stewart-Williams,S. (2007). Altruism Among Kin vs. Non-kin: Effects of Cost of Help and Reciprocal
Exchange. Evolution and Human Behavior, 28(3), 193-198.
Discussion Questions
 Who would donate their kidney to a sibling?
 Cousin?
 Friend?
 Acquaintance?
 Stranger?
 How do you think we can explain the level of helping
given to friends despite their lack of genetic
similarity? How can proximity be used to explain it?
Stewart-Williams,S. (2007). Altruism Among Kin vs. Non-kin: Effects of Cost of Help and Reciprocal
Exchange. Evolution and Human Behavior, 28(3), 193-198.