Your decisions are what you eat

The old suspicion that wars are caused by a leader’s indigestion does not seem so far-fetched in the light of accumulating evidence that our metabolic state can influence rational decisionmaking and our approach to risk. For decades, scientists have demonstrated links between the availability and quality of food and behaviour in animals, but it is only recently that these studies have been extended to humans, with potential implications for governments, corporations and individuals in positions of power. The results confound conventional wisdom that has held that metabolic conditions in response to factors such as eating and exercise have no impact on fundamental decisionmaking processes; rather, these have been held to be driven purely by external factors. “The traditional economic literature and theory regards the internal workings of individuals’ brains as a “black box”, contributing noise to the decision-making process, but without acknowledging the potential for systematic decision-making biases arising from purely biological factors,” commented Mkael Symmonds at the Department of Clinical Neurology at Oxford University in the UK. However, not all economists and psychologists have been blind to the role of metabolic factors in critical decisionmaking. Daniel Kahneman, who was a professor of psychology at Princeton University (USA), and won the Nobel Prize for Economics in 2002 for his work on the psychology of judgement and decisionmaking, gives several examples in his book Thinking Fast and Slow [1]. The most famous of these was based on a study of Israeli judges showing that the proportion of requests for parole that were granted peaked just after lunch and then decreased as a function of time during the rest of the day [2]. Kahneman concluded that hungry or “ego-depleted” judges tend to give less careful consideration to details of the cases, and would more often reach the safe position of denying parole requests. If matters as important as parole requests are influenced by an individual’s metabolism, it is not a great stretch to conclude that this might also apply to decisions made by others in positions of power.