Mental fatigue and decision-making

One of the less understood and least discussed areas of public policy is the influence of psychological and behavioural motivations in determining the actions and decisions of human beings. Conventional wisdom on this has relied on the assumption that human beings are rational and respond to incentives (rewards and punishments) and regulations (rules). But this approach overlooks the critical influence of cognitive biases on human behaviour.

An excellent post in Economix draws attention to the critical role of extraneous, human behaviour-related factors in deciding outcomes in public administration. It points to a recent paper by Shai Danzigera, Jonathan Levavb and Liora Avnaim-Pessoa who analysed the changes in the nature of decision-making by eight experienced parole judges in Israel during a court session.

They examined more than 1,000 rulings made by them in 2009 found that the probability of favorable decisions declined dramatically as the session progressed. They write,

"Are judicial rulings based solely on laws and facts? Legal formalism holds that judges apply legal reasons to the facts of a case in a rational, mechanical, and deliberative manner. In contrast, legal realists argue that the rational application of legal reasons does not sufficiently explain the decisions of judges and that psychological, political, and social factors influence judicial rulings. We test the common caricature of realism that justice is “what the judge ate for breakfast” in sequential parole decisions made by experienced judges. We record the judges’ two daily food breaks, which result in segmenting the deliberations of the day into three distinct “decision sessions.” We find that the percentage of favorable rulings drops gradually from ≈65% to nearly zero within each decision session and returns abruptly to ≈65% after a break. Our findings suggest that judicial rulings can be swayed by extraneous variables that should have no bearing on legal decisions."

A Guardian report quotes one of the authors, Jonathan Levav,

"You are anywhere between two and six times as likely to be released if you're one of the first three prisoners considered versus the last three prisoners considered."

This finding resonates with studies elsewhere and in other areas. Behavioural economists like Dan Ariely have found that making successive decisions depletes a limited mental facility. As people get tired, they look for shortcuts, and one of the easiest shortcuts is to uphold the status quo – in this case, denying parole. As the Economix report writes about its implications elsewhere,

"This suggests that college admissions committees are more likely to accept the first applicants they consider after a lunch break. Or that quality-control officers may be more likely to ignore possible flaws in products as a long day drags toward its close."

As the Economix post argues, while food and rest are imperfect solutions to overcome mental fatigue related problems, checklists may be more effective in addressing them. In fact, Prof Levab points to the extensive use of checklists by professionals like pilots as an acknowledgement of the reality of mental fatigue.

Update 1 (7/6/2011)

The idea of depletable self-control - that an individual’s capacity for exerting willpower was finite (or exerting willpower in one area makes us less able to exert it in other areas) has been gaining currency in recent years. In 1998, researchers at Case Western Reserve University published some of the young movement’s first returns. Roy Baumeister, Ellen Bratslavsky, Mark Muraven, and Dianne Tice set up a simple experiment. They had food-deprived subjects sit at a table with two types of food on it: cookies and chocolates; and radishes. Some of the subjects were instructed to eat radishes and resist the sweets, and afterwards all were put to work on unsolvable geometric puzzles. Resisting the sweets, independent of mood, made participants give up more than twice as quickly on the geometric puzzles. Resisting temptation, the researchers found, seemed to have "produced a 'psychic cost'".

Over the intervening 13 years, these results have been corroborated in more than 100 experiments. Researchers have found that exerting self-control on an initial task impaired self-control on subsequent tasks - consumers became more susceptible to tempting products; chronic dieters overate; people were more likely to lie for monetary gain; and so on.

In addition to self-control decisions, researchers have found the same problem with tradeoff decisions - where w resolve conflicts among choices as rationally as possible. Any decision that requires tradeoffs - like choosing between more money and more leisure time - require the same conflict resolution as self-control decisions and seems to deplete our ability to muster willpower for future decisions.

Princeton economist Dan Spears has found that such self-control and trade-off decisions are more pervasive for poor people, with the result that they make a large number of sub-optimal subsequent decisions. For example, if you have enough money, deciding whether to buy the soap only requires considering whether you want it, not what you might have to give up to get it. However, many of the tradeoff decisions that the poor have to make every day are onerous and depressing - whether to pay rent or buy food; to buy medicine or winter clothes; to pay for school materials or loan money to a relative - are weighty, and just thinking about them seems to exact a mental cost.

Mullainathan and Banerjee too found that given their scarce incomes, the same self-control or trade-off decision problem is more consequential for the poor than the rich. These findings bring in a new dimension to poverty - "poverty doesn’t simply reduce freedom by constraining an individual’s choices, but that it may actually alter the nature of freedom by reducing an individual’s willpower".