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Interpersonal Decisions Notes

Psychology Notes > Individual Differences (2nd year) Notes

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Interpersonal decisions
Genetic studies
Wallace et al., 2007: observed MZ and DZ twins' performance on ultimatum game and found a positive correlation between acceptance thresholds of MZ twins, and no correlation between DZ
twins' acceptance thresholds
 Genes also contributed to 42% of the variance in responder behaviour, suggesting a modest genetic effect
Knafo et al., 2008: found that RS3 length (region of DNA that regulates expression of vasopressin)
correlates with higher levels of hippocampal messenger RNA for vasopressin 1a receptor i.e. longer
RS3 promotor region means more vasopressin receptors
 It was found that people homozygous for RS3 long allele are more generous than those homozygous for RS3 short allele, so vasopressin signaling mediates individual differences in generosity in dictator game

Dominance and Reputation building
Burnham, 2007: found that high T men reject low ultimatum game offers ($5 or $25 of $40)
 High testosterone men perceive low offers as a threat/challenge
Zak et al., 2009: artificially raised T levels  leads to higher acceptance threshold, so reject low offers in ultimatum game
Harris et al., 1998: found that identical twins have similar levels of T (r>0.6), compared to fraternal twins (r is between -0.01 and -0.34) suggesting a genetic effect in testosterone level
 Some genetic effect on ultimatum game, as high T men and women reject low offers

Pro-sociality: Fairness, altruism, and social norms
Crockett et al., 2008: decreased serotonin level increase rejection of unfair offers in UG  makes us less tolerant to unfairness
Takahashi et al., 2012: found that rejection rates of unfair offers in UG are positively correlated with trust (r=0.54) and straightforwardness (r=0.59) subscales of agreeableness
 Genetically moderated as these traits are heritable (h 2>0.3)
 Negative correlation between rejection of unfair offers and amount of serotonin transporter in dorsal raphe nucleus (r=-0.5). This is also negatively correlated with straightforwardness and trust so genetic serotonergic contributions predict trust which in turn partially predict acceptance threshold
Motivation to maximize monetary gain
BAS-drive and -reward responsiveness, and SR involved
Scherres and Sanfey, 2006: found that scores on BAS-D and BAS-RR was correlated with higher offers in ultimatum game, and lower splits in dictator game, as they want to maximize the difference between ultimatum game offer and dictator game allocation - reflecting strategic thinking

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