Kin Selection Theory. Overview. Methods of Kin Recognition. The Trust Game. Hypotheses. The Trust Game

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Stuart Stone
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1 Overview What are the links between kin recognition and facial resemblance? How does facial resemblance affect behaviour in an economic game? Can those results be explained in terms of differential attractiveness of resembling faces? Kin Selection Theory Relatives other than your direct offspring can share your genes. Helping them to reproduce can increase your own fitness. If organisms do show differential treatment to kin according to the degree of relatedness, how do they detect kinship? Methods of Kin Recognition Social Cues Proximity Association Verbal Phenotype Matching Self-referential Other-referential The Trust Game subjects played games with different pictured online participants. Game You are player. Please make your choice. Player YOU 8 games were played with self-morphs and 8 were played with non-self morphs. P = $ = $ P = $ = $ P = $ = $ Hypotheses People will show more in self morphs than they will in non-self morphs. People will show more (less selfishness) towards self morphs than they will towards non-self morphs. The Trust Game P ing selfish not ing fair P = $X = $X P = $X+ = $X+ P = $X- = $X+ X =,, or (after Eckel & Wilson, 998)

Sample Game Game You are player. Please make your choice.

P = $ = $ as Player as Player 8 w/ non-self morphs as Player

Player Shape-Only ing Shape-Colour ing shape-colour morph

shape-only morph unknown % Trust and Fairness number of

2 Sample Game Game You are player. Please make your choice. Transformations s played games 8 w/ self morphs YOU P = $ = $ P = $ = $ as Player as Player 8 w/ non-self morphs as Player as Player P = $ = $ in one of two configurations. Player Shape-Only ing Shape-Colour ing shape-colour morph Shape-Colour unknown % self or non-self % Shape-Only shape-only morph unknown % Trust and Fairness number of responses self or non-self % Self morphs Non-self morphs Shape-colour morphs Shape-only morphs

number....... * D =.8 * p =. t-test p =. Wilcoxon Trust and Fairness self morphs non-self morphs D = -.

Hamilton s Rule r > c/b s were run in the same task using morphs made from famous and non-famous faces

Altruistic behaviour can be selected for if : the cost (c) to the donor is less than the benefit (b) to

When does it pay to play fair?.. Probability plays fair (u).

3 number * D =.8 * p =. t-test p =. Wilcoxon Trust and Fairness self morphs non-self morphs D = -. number Control Experiment D = -.9 self morphs non-self morphs D =. What About Familiarity? Hamilton s Rule r > c/b s were run in the same task using morphs made from famous and non-famous faces found on the internet. No differences were found in ing or towards famous and non-famous morphs. Altruistic behaviour can be selected for if : the cost (c) to the donor is less than the benefit (b) to the recipient multiplied by the relatedness (r) between the donor and recipient When does it pay to? When does it pay to play fair?.. Probability plays fair (u). ing has a larger payoff not ing has a larger payoff.. Relatedness (r) Probability plays fair (u). ing and playing selfish ing and playing fair not ing and playing selfish.. Relatedness (r)

Attractiveness of Self-s Conclusions Fairness in this task is not affected by facial resemblance,

Facial resemblance enhances ing behavior in this task. But why?

Do people perceive self-morphs to be more attractive than others find those same images?

Penton-Voak, Perrett and Pierce (999) investigated this question with male morphs of female

4 Attractiveness of Self-s Conclusions Fairness in this task is not affected by facial resemblance, possibly because the payoff structure is not sufficient to elicit differential. Facial resemblance enhances ing behavior in this task. But why? s perceive self-morphs as having a greater relatedness? Self-morphs are more attractive? Do people perceive self-morphs to be more attractive than others find those same images? s offer more to attractive people in a hypothetical dictator game (Hancock). Penton-Voak, Perrett and Pierce (999) investigated this question with male morphs of female subjects. Other-Sex Self-s Same-sex % Shape % Colour s (Penton-Voak, Perrett & Pierce, 998) Making Same-Sex s % shape % colour % shape % colour Making Other-Sex s Same-sex % shape % colour

Groups of Seven Click on the face you find more attractive. Analysis Differential Attractiveness. self excluding minus self...8.

5 Groups of Seven Click on the face you find more attractive. Analysis Differential Attractiveness. self excluding minus self Differential Attractiveness males (n=). -. Measuring Resemblance females (n=) s Differential Resemblance. male self-morphs female self-morphs. Differential Resemblance Resemblance was measured by 8 independent observers, who rated each pair on a -point Likert scale. (Cronbach s alpha =.7) male self-morphs female self-morphs males (n=) -. females (n=) s

Facial resemblance increases the attractiveness of same-sex faces more than other-sex faces

Facial resemblance increases the attractiveness of same-sex faces more than other-sex faces Lisa M. DeBruine McMaster University Reactions to facial self-resemblance could reflect either specialized responses