Leonard Green

Leonard Green
Professor of Psychology, Economics at Washington University (St. Louis)

Len Green received his undergraduate degree from the City College of New York (CCNY) and his PhD from the State University of New York at Stony Brook. After completing post-doctoral research, he ventured west of the Mississippi (despite thinking he still was east of the river) where he is Professor of Psychology and Professor of Economics at Washington University in St. Louis, as well as Director of Undergraduate Studies. His research concerns choice and decision-making in rats, pigeons, and people, with a particular interest in models of self-control, impulsivity, and choice and decision-making. He is one of the developers of ‘behavioral economics,’ a transdisciplinary field that combines the experimental methodology of psychology with the theoretical constructs of economics. He is co-author of the book Economic Choice Theory: An Experimental Analysis of Animal Behavior, and editor of Advances in Behavioral Economics, the third volume of which is subtitled Substance Use and Abuse. His research has been funded by the National Institutes of Health, National Institute on Aging, and the McDonnell Center for Higher Brain Function. He served on the Executive Board of the Society for the Quantitative Analysis of Behavior (SQAB), was President of the Society for the Experimental Analysis of Behavior (SEAB), and was Editor of the Journal of the Experimental Analysis of Behavior. He is a Fellow of the Association for Behavior Analysis International (ABAI) and the Association for Psychological Science (APS), and is Past-President of Division 25 (Behavior Analysis) of the American Psychological Association.


Impulsivity, Impatience, and Risk Taking:
How Many Impulsivities? A Discounting Perspective


People discount the value of delayed or uncertain outcomes, and the same mathematical function describes both delay and probability discounting. The degree to which individuals discount is thought to reflect how impulsive they are. From this perspective, steep discounting of delayed outcomes (which fails to maximize long-term welfare) and shallow discounting of probabilistic outcomes (which fails to adequately take risk into account) reflect similar decision-making processes and also the same trait of impulsivity. However, several manipulations selectively affect delay and probability discounting, and correlational studies show that how steeply one discounts delayed rewards is relatively independent of how steeply one discounts probabilistic rewards. Thus, referring to both delay and probability discounting as measures of ‘impulsivity’ may serve only to indicate that real behavioral problems can involve either kind of discounting. This talk will highlight the similarities and differences between delay and probability discounting as well as the implications of both experimental and correlational findings on discounting and impulsivity.