Pigeons Go for the Big Money

Blue Rock Pigeon. Picture by J.M. Garg from Wikipedia.org

We all have a tendency to do things we know are not good for us like overeating, putting off to tomorrow what we could do today, failing to save for retirement, etc..  One reason for some of these behaviors is that we value immediate rewards over more distant ones.  Studies in species from fish and birds to primates including humans have shown that animals prefer a smaller reward (such as food or money) immediately to a larger reward in the future.  For example if given a choice pigeons will choose to receive a smaller number of food pellets immediately over a larger number of pellets later.  Similarly human subjects will choose to receive a smaller amount of money today rather than receive a larger amount of money weeks or months down the road.  In both these cases if the future rewards become large enough  then the larger reward will be chosen.  Thus we tend to "discount" future rewards and perceive immediate rewards as being more valuable.  This may help explain why I am driven to continue to spend time watching my favorite TV show even though I know that I will be happier in the long term if I spend that time working out or writing manuscripts.  Researchers have used the study of delay discounting to understand human behaviors such as procrastination and addiction. 

A recent paper by Zentall and Stagner in the Proceedings of the Royal Society B (278:1203-1208) uses a similar paradigm to provide a model for human gambling behavior.  Pigeons were given the choice between a symbol that alway predicted a reward of 3 food pellets or another symbol that 80% of the time provided zero food pellets and 20% of the time provided 10 food pellets.  So over the course of 10 trials a pigeon that always went for the sure thing would receive a total of 30 food pellets while a pigeon that went for the possibility of a big payoff would receive 20 food pellets.  Despite the fact that the three pellet payoff was a better bet and resulted in acquiring more food over time the pigeons consistently chose to go for the more uncertain, larger reward.  Thus the pigeons, like human gamblers, were lured by the prospect of a big payout even though it was a bad strategy over time.  It appears that animals and humans are primed to value larger and/or immediate rewards over smaller but consistent rewards or rewards that occur later in time.