Short communicationDopamine, motivation, and the evolutionary significance of gambling-like behaviour

- Reward unpredictability is a source of motivation for birds and mammals.
- Reward unpredictability, like deprivation, enhances mesolimbic dopamine release.
- I argue that both motivate seeking behaviour to compensate a lack of predictability.

If given a choice between certain and uncertain rewards, animals tend to prefer the uncertain option, even when the net gain is suboptimal. Animals are also more responsive to reward-related cues in uncertain situations. This well-documented phenomenon in many animal species is in opposition to the basic principles of reinforcement as well as the optimal foraging theory, which suggest that animals will prefer the option associated with the highest reward rate. How does the brain code the attractiveness of unreliable/poor reward sources? And how can we interpret this evidence from an adaptive point of view? I argue that unpredictability and deprivation - whether physiological or psychological - enhance motivation to seek valuable stimuli for the same reason: compensating the difficulty an organism has to predict significant objects and events in the environment.