Hyper Incentives from a Visceral Brain

One issue for a psychologically-enriched economics is determining what would constitute an irrational choice. While we (people in general) have a sort of common-sensical notion that an irrational choice is one that does not make the person better off (or makes the person worse off), it's actually a pretty complicated question, especially given that our definition of "better off" could pertain to utility at many different points in time - the utility we perceive at the time of the experience, how we remember the experience later, how much we expect to enjoy it before hand, etc. (And of course, there is the separate problem that a decision, like eating an ice cream cone, could make the self that is eating it better off while making the self that later can't fit in his jeans worse off.)

This chapter by Kent Berridge, a biopsychologist at the U. of Michigan who studies the neuroscience of "liking" and "wanting" that drives choice behavior, defines irrational choice and looks at the situations in which it appears to occur. Notes and comments:

Berridge limits irrational choice to particular type of situation: "A truly irrational choice would be to choose what you expect not to like." He does not consider it irrational to choose something that turns out to yield low utility (e.g. seeing a movie that you ended up hating) because "rationality cannot be held responsible for the accuracy of my expectations, only for the consistency with which I act upon them." He also does not view as necessarily irrational choices that are influenced by, for example, the subliminal presentation of emotionally-charged stimuli (e.g. a happy or sad face) because it is possible that people's expectations have been changed without their knowledge. This is a narrower definition than some other researchers have used.

He draws a distinction between two types of liking or wanting:
(1) "Ordinary wanting" - a conscious desire that depends on the brain's cortical systems
(2) "Incentive salience" or "wanting" that causes a reward to become momentarily more intensely attractive and sought and that is mediated by the brain's dopamine systems

Because "of course we would never use a human infant in an affective neuroscience experiment," Berridge and his colleagues have done most of their experiments on rats. They use typical animal behavior associative learning techniques, like teaching a rat to press a lever in order to get a reward and presenting a reward with a cue (a la Pavlov's dog). They are able to measure how much a rat wants something by how much he will press the lever to get it (since pressing the lever is a kind of work that can result in getting the reward).

Berridge has been able to trigger irrational choice in rats when two factors are present:
(1) the rats have been injected with amphetamine (activating their dopamine systems)
(2) they are given a reward cue (e.g. light or sound that has previously been presented with sugar, conditioning the rat to associate the cue with sugar)

Under these conditions, the dopamine-activated rat wants sugar in an ordinary sense; then it is presented with the reward cue, which triggers an additional sense of exaggerated "wanting" in the rat (and it presses the bar at a much higher rate - 4 times as much as when the cue is not present); then it returns to its rational level of wanting (and the baseline level of pressing the bar). Later, the cue is presented again and the intense "wanting" returns. Interestingly, when the rats are under the influence of amphetamine, they do not demonstrate a higher level of positive facial expressions when given sugar, which researchers interpret as the rat not having an increased liking or enjoyment of sugar when dopamine-activated. They "want" the sugar more, but do not enjoy it more.



The researchers make the natural extension to drug-addicted humans, who even after achieving a long period of abstinence can be influenced by drug cues (things they associate with doing drugs) to relapse.

Berridge notes that "if irrational choice occurs at all in normal human life, the situations that will produce it will be relatively rare... It would require high exciteability in mesolimbic 'wanting' systems and the simultaneous encounter with reward cues." I don't know. I personally experienced this feeling of "wanting" or incentive salience, in which I felt the overwhelming compulsion to have something I knew I didn't really want that much, the most strongly when (a couple years ago) Robert brought home and opened up a box of Cracklin' Oat Bran cereal, henceforth referred to by us as Oat Crack. But maybe that doesn't count as "normal human life."

Reference: The psychology of economic decisions / edited by Isabelle Brocas and Juan D. Carrillo. New York: Oxford University Press, 2003.