Asymmetry of reinforcement and punishment in human choice

Abstract

The hypothesis that a penny lost is valued more highly than a penny earned was tested in human choice. Five participants clicked a computer mouse under concurrent variable-interval schedules of monetary reinforcement. In the no-punishment condition, the schedules arranged monetary gain. In the punishment conditions, a schedule of monetary loss was superimposed on one response alternative. Deviations from generalized matching using the free parameters c (sensitivity to reinforcement) and log k (bias) were compared in the no-punishment and punishment conditions. The no-punishment conditions yielded values of log k that approximated zero for all participants, indicating no bias. In the punishment condition, values of log k deviated substantially from zero, revealing a 3-fold bias toward the unpunished alternative. Moreover, the c parameters were substantially smaller in punished conditions. The values for bias and sensitivity under punishment did not change significantly when the measure of net reinforcers (gains minus losses) was applied to the analysis. These results mean that punishment reduced the sensitivity of behavior to reinforcement and biased performance toward the unpunished alternative. We concluded that a single punisher subtracted more value than a single reinforcer added, indicating an asymmetry in the law of effect.

Fig 1

Log response ratios (y-axis) plotted against log net-reinforcer ratios (reinforcers delivered minus reinforcers removed; x-axis) for the 5 participants under no-punishment (open circles) and punishment (closed circles) conditions.

Fig 2

Mean log reinforcement ratio in the reinstated no-punishment condition plotted as a function of the mean log reinforcement ratio of the initial no-punishment condition. Each point represents the mean of the last three sessions of each schedule for each participant.

Fig 3

Values for bias (log k; top panel) and sensitivity to reinforcement (c; bottom panel) parameters for the no-punishment (open circles), punishment-net (closed circles), and punishment-obtained analyses (closed diamonds). In the top panel, the horizontal line represents the bias value under perfect matching (log k  =  0); in the bottom panel, the horizontal line represents the sensitivity value under perfect matching (c  =  1). Dashes represent means.