Molecular genetics of economic decision
|Speaker:||Richard Epstein & Soo Hong Chew, National University of Singapore|
|Date:||Friday 13 June 2014|
This talk is based on a large scale study of the molecular genetics of choice behaviour involving more than 3000 Han subjects in China and in Singapore who each contributed blood or saliva samples. We analysed subjects’ DNA and observed their choice behaviour in incentivized tasks involving both individual decision making, such as risk, ambiguity, and time, and social decision making, including other regarding behaviour (such as altruism, fairness, envy, and trust) and strategic thinking (inferred from auctions and the p-beauty game). This talk will focus on two specific findings (see appended abstracts). One is based on risk taking behaviour observed over three individual choice tasks. Another finding concerns a sense of indignation elicited from responders’ behavior in a standard ultimatum game in contrast with their behavior in a modified ultimatum game with a randomized proposer. Time permitting, I will discuss additional findings such as those based on telomere length, hormonal response, and gene expression.
Risk attitude estimated from behavior in individual choice tasks: Individual differences in risk attitudes being moderately heritable suggest that specific genes can be identified that partially predict financial risk taking behavior. By implementing a molecular genetic strategy to gene identification, a few first studies found that the exon III VNTR polymorphism of the dopamine D4 receptor (DRD4) gene is linked to financial risk attitude, measured in an experimental portfolio choice task, among several small samples of Caucasian subjects. In the current study we re-examine this finding in a large sample of 3433 Han Chinese undergraduate subjects using two additional choice tasks – even-chance bet and sure-bet – and find that each measured risk attitude was associated with DRD4. Using a computational approach, we estimated subjects’ risk aversion coefficient in an expected utility model and found that it remains significantly associated with DRD4 with the most common exon III 4R/4R genotype being associated with greater risk aversion. This result supports the implication of the model in Zhong et al. (2009) linking dopamine tone to risk attitude based on neurochemistry. Overall, this study contributes to a computational approach towards understanding the biological basis of decision making under risk.
Indignation elicited from responder behavior in ultimatum games: Intention looms large in social cognition and moral reasoning and humans are exquisitely fine-tuned to perceive the intentions of others. Depending on intention we make judgments with profound implications in business, government, and international relations. In a controlled experiment using a modified ultimatum game, we conduct a genome-wide association (GWA) study of individual differences in sensitivity to fairness intention (“it’s the thought that counts”). GWA in the discovery sample of 2655 (p = 1.31 x 10–8) was replicated in a second group (p = 0.0018), and in the pooled sample (N = 3157) the meta p value was 8.93 x 10–11 (R2 = 0.0104). The identified SNP is in the short 7th intron of TRIP8b a gene that encodes a critical accessory subunit of brain HCN channels, which is important in dopamine transmission. Our findings derived from a choice-based phenotype precisely elicited in an experimental economics laboratory setting suggest a singular strategy for uncovering the genetic architecture of economic decision making.