The Law of Expect or a Modified Law of Effect
We review converging lines of evidence describing the negative relationship found between the signaled probability of food and response variation. This relationship is quite general: It is observed in both temporal and spatial behavioral dimensions, in both rats and pigeons, and in both the operant chamber and in open field settings. Response variation is also greater under conditions involving smaller or delayed food rewards compared to larger or immediate rewards. These data support a new Law of Expect which states that outcome expectation is a determinant of response variation, with variation increasing or decreasing with a decrease or increase in outcome expectation, respectively. By comparison, we present simulations of a Modified Law of Effect extending the explanatory power of Thorndike's original Law. While this Modified Law of Effect has improved explanatory power, it fails to account for all of the empirical data. The Law of Expect also fails to account for all of the empirical phenomena. Thus, both Laws are necessary. Investigations into the neural basis of these laws may lead to new insights into the generation and regulation of creative behavior and to a better understanding of the neural systems involved in learned behavior.