An animal model of human gambling behavior

Human gambling almost always results in a loss. Thus, it is generally assumed that humans gamble for enjoyment and the enticement of winning. Although animals are purported to engage in optimal foraging behavior and should be sensitive to the probability of reinforcement, similar suboptimal behavior can be found in pigeons and other animals. They show a preference for an alternative that is associated with a signal for a low probability of a large reward (e.g., 20% probability of 10 pellets - a mean of 2 pellets) over an alternative that is associated with a signal for a high probability of a smaller reward (100% probability of 3 pellets). This effect may result from the strong conditioned reinforcement associated with a stimulus that is always followed by a reinforcer, but surprisingly, little conditioned inhibition associated with the signal for the absence of a reinforcer. A similar mechanism appears to be responsible for human gambling (gamblers tend to overvalue wins and undervalue losses). We have also found that for pigeons (and perhaps humans as well), the probability of the conditioned reinforcer is relatively unimportant, it is primarily the value of the reinforcer when it does occur (e.g., 10 pellets vs. 3 pellets) that is important. Interestingly, pigeons show several other parallels to human gambling behavior. For example, hungrier pigeons show a greater tendency to choose suboptimally. Also, pigeons that have had enrichment in the form of social experience in a larger cage show a reduced tendency to choose suboptimally. This animal model may provide a useful analog to human gambling behavior, one that is free from the influence of human culture, language, social reinforcement, and other experiential biases that may encourage human gambling.