Serotonin transporter gene-linked polymorphic region (5-HTTLPR) influences decision making under ambiguity and risk in a large Chinese sample

Abstract

Risky decision making is a complex process that involves weighing the probabilities of alternative options that can be desirable, undesirable, or neutral. Individuals vary greatly in how they make decisions either under ambiguity and/or under risk. Such individual differences may have genetic bases. Based on previous studies on the genetic basis of decision making, two decision making tasks [i.e., the Iowa Gambling Task (IGT) and Loss Aversion Task (LAT)] were used to test the effect of 5-HTTLPR polymorphism on decision making under ambiguity and under risk in a large Han Chinese sample (572 college students, 312 females). Basic intelligence and memory tests were also included to control for the influence of basic cognitive abilities on decision making. We found that 5-HTTLPR polymorphism significantly influenced performance in both IGT and LAT. After controlling for intelligence and memory abilities, subjects homozygous for s allele had lower IGT scores than l carriers in the first 40 trials of the IGT task. They also exhibited higher loss aversion than l carriers in the LAT task. Moreover, the effects of 5-HTTLPR were stronger for males than for females. These results extend the literature on the important role of emotion in decision making under ambiguity and risk, and shed additional lights on how decision making is influenced by culture as well as sex differences. Combining our results with existing literature, we propose that these effects might be mediated by a neural circuitry that comprises the amygdala, ventromedial prefrontal cortex, and insular cortex. Understanding the genetic factors affecting decision making in healthy subjects may allow us to better identify at-risk individuals, and better target the development of new potential treatments for specific disorders such as schizophrenia, addiction, and depression.

Figure 1

A) Illustration of the Iowa Gambling Task. Subjects were instructed to choose one card at a time from 4 decks of cards (labeled A, B, C and D). Green bar (the lighter one) on the top represents money in his/her wallet which changed in length as he/she “wins” or “loses”. Red bar (the darker one) represents his/her loan (2000 yuan). B) IGT score (number of choices from “good” decks minus choices from “bad” decks) showed a linear improvement over 5 blocks (20 cards each). Error bars indicate standard errors. Please note that to protect the validity of the IGT test, the payoffs on the cards are just for illustration purpose, and were not the actual ones subjects received in the task.

Figure 2

A) A sample trial of the Loss Aversion Task. On each trial, subjects were presented a display showing the amount of potential gain (in green) and loss (in red). They had to decide to what extent they would like to play this gamble. B) Color-coded heatmap of probability of gamble acceptance at each level of gain/loss. C) Color-coded heatmap of probability of response times (sec) at each level of gain/loss.

Figure 3

A) 5-HTTLPR polymorphism had a significant effect on decision under ambiguity (the first 40 trials) but not on decision under risk (the last 60 trials) tested by IGT. Subjects with l allele (l carriers) had a significantly higher mean IGT score than s allele homozygotes on the first 40 trials of IGT. Moreover, this effect was modulated by gender, with only males showing the effect. But for the last 60 trials of IGT, although there was no effect of 5-HTTLPR polymorphism, the IGT score was modulated by gender. Males chose more advantageous cards than females. B) 5-HTTLPR also influenced the loss aversion parameter λ tested by LAT task. Subjects homozygous for sallele showed higher λ value than l carriers. Error bars indicate standard errors.