How Rational is a Rat?

Just how clever is that rat? Is he a lazy, sneaking creature who will swipe any easy snack or is he a virtuous hard worker who will toil until he earns his just rewards? Perhaps a similar quandary has faced you: do you enroll in school and live on limited funds in the hope of later prosperity or do you get a job and enjoy life's rewards now. Moral judgments of work aside, the Discovery's channel's "Animal Planet" website reports on the work a group of researchers has come up with a relatively simple test apparatus to address this question in the rat. It consists of a simple maze shaped as a "T". If the rat goes in one direction it will quickly find a small treat - a single sugar cube. If the rat travels the other way, he will have to do some work, but will get a larger number of sugar cubes.

The researchers, lead by Ruud van den Bos of Utrecht University in The Netherlands, wanted to know about the decision-making process of the rat, not just whether he was lazy or slothful. What they did was to vary the "hard road" in two ways. First they varied the size of the reward by changing the number of sugar cubes. Second, they changed just how hard it was to get to the bigger reward by changing the height of the wall the rat had to climb.

What they discovered was that there was a critical point at which the rat would abandon the harder route and go for the reward and that this critical point was based both on the size of the rewards and on the height of wall to be scaled. What the researchers claim that this shows is that the rats were conducting a "cost-benefit analysis, rather than basing their decision on a single factor such of labor or reward. This cost-benefit analysis turns out to be relatively sophisticated. It is claimed that this is the first time that non-human animals have been shown to make decisions using a mathematical relationship called an "internal constant standard" which is an individual's ratio of effort to reward.

Full details of the research will be published in the journal Behavioral Brain Research. (Correction: The article is available in the August 2006 issue of Behavioral Brain Research.) Readers interested in finding out more about van den Bos's other research relating to motivation in rats without waiting can also check out a draft chapter of a book van den Bos is contributing to (Go up one directory level to get some commentary.).

As interesting as this research was, there was no investigation of what other species might do in the same circumstances. An interesting question here is whether the rat's rational approach is rare or common in the animal kingdom. Given the relative simplicity of the experiment it would have been easy to do for other animals, including humans. (Humans have been shown to be highly motivated by sugary snacks, so recruiting volunteers should not be too hard.) It would be interesting to measure the "internal constant standard" of various people put in the maze with sugary snack and compare the results to life choices, such as pursuing training that will lead to higher income or to measures of depression.

Posted by Jonathan Caplan (3)

Update 9/26/2006

The "Marshmallow Studies," mentioned by one of my commenters, had so much online writing about them without any sources cited and so much conflict about facts of the study that I began to wonder if it the study was, in fact, an urban myth. The original studies were real, though, and conducted by Walter Mischel at Stanford from 1968 to 1974 (Journal of Social Psychology 1970, 1975), with later follow-ups. (Science 1989, 244, 933-938.) Most of the reports got the basic idea right with an amusing diversity of details. Here's how it really went down: First, the children could choose the reward they prefered - usually a two marshmallows instead of one or a five pretzels instead of two small cookies. Second, the kids, age 3 to 5 were told that they could choose to eat the snack immediately and then ring a bell or wait ~15 minutes for the researcher returned from his "errand" and receive the greater reward. Results were obtained in follow-up studies over decades of a group of ~500 people. First, it was observed that the kids who were able to wait did so by not focusing on the reward using strategies such as singing to themselves or covering their eyes. These kids were using strategies rather than pure willpower. Later when they were 10 years old the kids who waited for greater reward had fewer behavioral problems. In high school, they had higher SAT scores and at age 32, they had fewer drug problems. On the other hand the kids who wanted the immediate reward handled stress more poorly, got into more fights and had higher incarceration rates. One thing that these studies did not address, though was whether the kids who choose the immediate result were making rational choices based on their life experience. Perhaps those kids had parents or caregivers who often did not follow through on promises and learned that the best strategy for succeeding in their environment was to get what you could as soon as it was available. The rats may have had the advantage of consistant behavior in their overseers.

As to my other commenter, I too wondered about adults, though more about individual circumstance than issues of culture. I'm not sure what you meant about a mathematical equation for rat foraging. Perhaps one could attempt to derive one from the experimental results or from an analysis of what whould be optimal in a given natural environment. They were certainally shown to have a ratio of work to reward that they employed in their choices in the experiment.

-Jonathan Caplan