Scaling relative incentive value in anticipatory behavior

Papini and Pellegrini (Papini, M. R., & Pellegrini, S. Scaling relative incentive value in consummatory behavior. Learning and Motivation, in press) observed that, within limits, the level of consummatory responding of rats exposed to incentive downshifts in the concentration of sucrose solutions was similar when the ratio of test/training solutions was the same. For example, 32 → 4% and 16 → 2% downshifts (1:8 test/training ratios) lead to similar levels of consummatory behavior, despite differences in the absolute concentrations of the solutions involved in the downshift. This suggests the applicability of Weber’s law to spaced-trial, incentive-downshift situations. Experiment 1 extended these results to runway performance using food pellets as reward, and Experiment 2 to lever pressing performance, using an autoshaping procedure and sucrose solutions as rewards. The results conform well to the test/training ratio suggesting that Weber’s law is applicable to anticipatory behavior. A simple mathematical rule that can be easily incorporated into models based on linear operators describes the results of consummatory and anticipatory behavior experiments.