Pavlovian processes may produce contrast leading to bias and suboptimal choice

Pavlovian processes are likely responsible for the varied contexts in which contrast occurs between what is expected and what is obtained. Such contrast effects result in paradoxical biases and even suboptimal choice by animals. For example, pigeons prefer a suboptimal alternative that results in a stimulus signaling a low probability (20%) high reward (ten pellets) over an optimal alternative that results in a stimulus signaling a high probability (100%) of a smaller reward (three pellets). This effect is analogous to human unskilled gambling. In another case, pigeons prefer a stimulus that has required many pecks to obtain over one the has required one peck to obtain (a so-called justification of effort effect). In a third line of research that investigated the preference for risky choice over safe choice, pigeons chose between two alternatives, a safe choice that resulted in two pellets of food, or a risky choice that resulted in either one or three pellets of food. In general, the pigeons preferred the risky alternative, but importantly, their choice was influenced by whether the choice reflected a gain or a loss - the difference between what was shown to them (one, two, or three pellets) and what they received. Each of these lines of research suggest the importance of contrast effects produced by Pavlovian processes that result in biases or suboptimal behavior.