Neuroethics & Law Blog

Endowment Effect and Chimpanzees

Owen Jones, Sarah Brosnan, et al. discuss work on the endowment effect in the articles below:

"Law, Biology, and Property: A New Theory of the Endowment Effect"

William & Mary Law Review, Vol. 49

OWEN D. JONES, Vanderbilt University - School of Law & Department of Biological Sciences
SARAH F. BROSNAN, Georgia State University - Department of Psychology
Recent work at the intersection of law and behavioral biology has suggested numerous contexts in which legal thinking could benefit by integrating knowledge from behavioral biology. In one of those contexts, behavioral biology may help to provide theoretical foundation for, and potentially increased predictive power concerning, various psychological traits relevant to law. This Article describes an experiment that explores that context.

The paradoxical psychological bias known as the endowment effect puzzles economists, skews market behavior, impedes efficient exchange of goods and rights, and thereby poses important problems for law. Although the effect is known to vary widely, there are at present no satisfying explanations for why it manifests when and how it does. Drawing on evolutionary biology, this Article provides a new theory of the endowment effect. Briefly, we hypothesize that the endowment effect is an evolved propensity of humans and, further, that the degree to which an item is evolutionarily relevant will affect the strength of the endowment effect. The theory generates a novel combination of three predictions. These are: (1) the effect is likely to be observable in many other species, including close primate relatives; (2) the prevalence of the effect in other species is likely to vary across items; and (3) the prevalence of the endowment effect will increase or decrease, respectively, with the increasing or decreasing evolutionary salience of the item in question.

The authors tested these predictions in a chimpanzee (Pan troglodytes) experiment, recently published in Current Biology. The data, further explored here, are consistent with each of the three predictions. Consequently, this theory may explain why the endowment effect exists in humans and other species. It may also help both to predict and to explain some of the variability in the effect when it does manifest. And, more broadly, the results of the experiment suggest that combining life science and social science perspectives could lead to a more coherent framework for understanding the wider variety of other cognitive heuristics and biases relevant to law.

"Endowment Effects in Chimpanzees"

Current Biology, Vol. 17, pp. 1704-1707, October 9, 2007
Vanderbilt Law and Economics Research Paper No. 08-13

SARAH F. BROSNAN, Georgia State University - Department of Psychology
OWEN D. JONES, Vanderbilt University - School of Law & Department of Biological Sciences
SUSAN P. LAMBETH, Michale E. Keeling Center for Comparative Medicine and Research
MARY CATHERINE MARENO, Michale E. Keeling Center for Comparative Medicine and Research
AMANDA S. RICHARDSON, Michale E. Keeling Center for Comparative Medicine and Research
STEVEN SCHAPIRO, Michale E. Keeling Center for Comparative Medicine and Research
Human behavior is not always consistent with standard rational choice predictions. The much-investigated variety of apparent deviations from rational choice predictions provides a promising arena for the merger of economics and biology. Although little is known about the extent to which other species also exhibit these seemingly irrational patterns of human decision-making and choice behavior, similarities across species would suggest a common evolutionary root to the phenomena.

The present study investigated whether chimpanzees exhibit an endowment effect, a seemingly paradoxical behavior in which humans tend to value a good they have just come to possess more than they would have only a moment before. We show the first evidence that chimpanzees do exhibit an endowment effect, favoring items they just received more than items they prefer that could be acquired through exchange. Moreover, we demonstrate that - as predicted - the effect is far stronger for food than for less evolutionarily salient objects, perhaps due to historically greater risks associated with keeping a valuable item versus attempting to exchange it for another. These findings suggest that the larger set of seeming deviations from rational choice predictions may be common to humans and chimpanzees, and that the evaluation of these through a lens of evolutionary relevance may yield further insights in both humans and other species.

Brain Tumors and Responsibility Case Study

Here is an excerpt from another guest post I wrote at the Volokh Conspiracy, a general interest law and policy blog.  I try to make the claim that, even if neuroscience were to have no direct, substantive impact on our carefully considered judgments about free will, it may nevertheless have an impact (at least a short term impact) on the attributions of responsibility made by laypeople when they are confronted with neuroscientific explanations of behavior:

   The neurolaw literature is typically addressed to one of two very different sets of issues. The first set is about responsibility. In particular, scholars ask whether we can justifiably hold people responsible for actions that are caused by activities in their brain for which they are not themselves responsible.

Consider the subject of this medical case study, who had no prior history of unusual sexual behavior. At around age 40, he began to demonstrate pedophilic behaviors (e.g., he made sexual advances toward his prepubescent stepdaughter). The man was found guilty of child molestation and given the opportunity to successfully complete a sexual addiction treatment program in lieu of going to jail. Unfortunately, he made sexual advances toward others in the treatment program and was forced to leave the program. Prior to being sent to jail, he complained of severe headaches and was taken to the hospital. Doctors soon discovered that he had a brain tumor in his orbitofrontal cortex. After the tumor was surgically removed, his sexual behavior returned to normal. You have to read the full case study for all the details. The bottom line, though, is that the study authors think it quite likely that the tumor played a causal role in the subject’s inappropriate behavior.

Many of my students have the intuition that the man should not be deemed criminally responsible for his sexual activities while he had the tumor. He is certainly not responsible for having the tumor, and it seems like the crime would not have happened but for the tumor. In most jurisdictions, however, I think the subject would be unlikely to mount a successful insanity defense.

If these issues about responsibility sound familiar, it’s because they are. This side of neurolaw often rehashes ancient questions about free will and agency (often without recognizing the questions as such). I do think that neuroscience offers a new perspective from which to explore these issues, and it goes something like this: As an empirical matter, our willingness to attribute responsibility to an actor (like the guy described above) tends to weaken when the person's actions seem to be caused by factors external to the actor. The more that we understand the causal mechanisms of human behavior, many of which will eventually be understood in neuroscientific terms, the less we tend to attribute responsibility to human agency. So, even if we’ve known for a very long time that our behavior is caused by events and circumstances beyond our control, somehow being made better aware of those causes seems to diminish, again as an empirical matter, our attributions of agency to particular human beings. These are not philosophical claims; they’re claims about human psychology. Nevertheless, interesting questions arise about what, if anything, follows from these psychological claims, assuming that they’re accurate.

My own work has principally focused on the second set of issues in neurolaw – namely, issues related to the legal and ethical implications of new neuroscience technologies... [End of excerpt].

Elephant Self-Recognition

Frans De Waal is guest blogging (or, at least, guest "q&a-ing") at the Freakonomics Blog.  In addition to his interesting answers in general, he provides this link to an Emory website with photos, videos, and other links to his work that aims to demonstrate that elephants can recognize themselves in mirrors.  (Actually, the link on the Freakonomics Blog to the Emory site doesn't work.  But I've linked to the site that he clearly intended to link to.)