Public Release: 

Researchers Identify Cognitive Process That Contributes To Gambling Behavior

American Psychological Association

WASHINGTON -- Gambling has always been a big business and as more states adopt lotteries and permit casino gambling it gets even bigger every year. From 1993 to 1994, the number of casino visits in the United States rose 35 percent to 125 million and those casino visitors left behind $16.5 billion in losses, more than twice as much as they lost in 1990. But if gambling is, overall, a losing proposition for the gambler, why do so many people do it?

Over the years, psychological researchers have identified several thinking processes that contribute to gambling behavior. These include biased evaluations of past gambling results (explaining away losses and viewing wins as evidence of gambling ability), the illusion of control (overestimating the influence one wields over outcomes and the probability of personal success) and the "gambler's fallacy" (the mistaken belief that over time, chance-determined outcomes will even out).

In the June issue of the American Psychological Association's (APA) journal Experimental Psychology: Applied, researchers from Central Michigan University and the University of Utah add another cognitive process to that list: selective hypothesis testing, that is, considering only one possible outcome when making decisions.

The researchers conducted a series of three experiments, in the first of which participants were asked to estimate the probability that a specific National Basketball Association team (one of four) would win the NBA championship and explain how. In the second experiment they were also asked to estimate the probability that a specific NBA team beat the point spread in an earlier game. In the third they were asked to estimate the probability that an NCAA basketball team (one of four) had won a computer-simulated playoff. In each experiment, participants were invited to place bets on the team they thought would win, had beaten the point spread or had won.

In each experiment participants who focused (as instructed) on a single team (as opposed to estimating the probability of winning for all four teams they were considering) consistently overestimated the probability of that team winning. In addition, study participants who overestimated that probability were more likely to place bets and larger bets than those who were not focused on a single team.

This overestimation of probability, the authors say, "could influence gambling decisions in any domain in which the potential gambler may focus on one possible outcome to the exclusion of others. Thus the blackjack player may be particularly interested in the likelihood of receiving a 10 after her or his first two cards sum to 11, the poker player may be particularly interested in the probability of making a straight on her or his next card, and the sports gambler may be particularly interested in the likelihood that the home team may win the league championship."

But, the authors note, selective hypothesis testing is avoidable. In one of the experiments, some participants (the control group) had to estimate the probability of each of four teams winning a computer-simulated championship. Under that condition, the participants overestimated the probability of winning for all four teams, indicating that they may have considered each team a viable contender. But these participants were less likely to gamble than those who had focused on only one team. "By encouraging potential gamblers to consider a wide number of potential outcomes, the appeal of any specific outcome is lessened and the likelihood that a bet will be placed is reduced," the authors write. "Thus, this specific cognitive strategy may counteract the influence of the selective hypothesis-testing process."

Not only might this strategy be useful in the treatment of problem gamblers, the authors suggest it might be useful in preventing gambling problems from developing. Training in abstract reasoning skills in secondary schools or college courses "could include a specific component that addresses the necessity of considering numerous potential outcomes when attempting to predict future events. This research suggests that such training could be relatively general in nature and still be readily applied by students to gambling and other risky choice situations."

Article: "The Effects of Selective Hypothesis Testing on Gambling," by Bryan Gibson, Ph.D., Central Michigan University, and David M. Sanbonmatsu, Ph.D., and Steven S. Posavac, Ph.D., University of Utah, in the Journal of Experimental Psychology: Applied, Vol. 3 No. 2.

(Full text available from the APA Public Affairs Office.)

Bryan Gibson, Ph.D. can be reached at (517) 774-4404 or at

The American Psychological Association (APA), in Washington, DC, is the largest scientific and professional organization representing psychology in the United States and is the world's largest association of psychologists. APA's membership includes more than 151,000 researchers, educators, clinicians, consultants and students. Through its divisions in 50 subfields of psychology and affiliations with 58 state, territorial and Canadian provincial associations, APA works to advance psychology as a science, as a profession and as a means of promoting human welfare.

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