Abstract||Detection and choice research have largely focused on the effects of relative reinforcer frequencies or magnitudes. The effects of punishment have received much less attention. This thesis investigated the effects of punishment on human signal-detection performance using a number of different procedures. These included punisher frequency and magnitude variations, different types of punishers (point loss & time-outs), variations in stimulus disparity, and different detection tasks (judgments of stimulus arrays containing either more blue or red objects, or judgments of statements that were either true or false). It examined whether punishers have similar, but opposite, effects to reinforcers on detection performance, and whether the effects of punishment were successfully captured by existing models of punishment and choice.
Experiment 1 varied the relative frequency or magnitude of time-out punishers for errors using the blue/red task. Participants were systematically biased away from the response alternative associated with the higher rate or magnitude of time-out punishers in two of three procedures. Experiment 2 varied the relative frequency of point-loss punishers using the blue/red task and the true/false task. Participants were systematically biased away from the alternative associated with the higher rate of point-loss punishers for the true/false task.
Experiment 3 examined the effects of punishment on response bias from a psychophysical perspective. Previous detection research which varied stimulus discriminability while holding reinforcers ratios constant and unequal (Johnstone & Alsop, 2000; McCarthy & Davison, 1984) found that a criterion location measure (e.g., c, Green & Swets, 1966) was a better descriptor of isobias functions compared to a likelihood ratio measure (e.g., log β[G], Green & Swets, 1966). Experiment 3 varied stimulus discriminability while holding punisher ratios constant and unequal. Like previous research, isobias functions were consistent with a criterion location measure.
Experiments 4, 5, 6, and 7 examined contemporary models of choice and punishment. Experiments 4, 5, and 6 varied the relative reinforcer ratio in detection tasks, both with and without the inclusion of an equal rate of punishment. Experiment 7 held the reinforcer ratio constant and unequal, and varied the durations of time-out punishers. Increases in preference (for the richer alternative) from reinforcer-only conditions to reinforcer + punisher conditions would support a subtractive model of punishment, while decreases in preference would support an additive model of punishment.
Experiment 4 was a between-groups study using time-out punishers. It supported the predictions of an additive model. Experiment 5 used three different procedures in a preliminary within-subjects design, evaluating which procedure was best suited for a larger within-subjects experiment (Experiment 6). In Experiment 6, participants sat four reinforcer-only and four reinforcer + punisher conditions where reinforcers were point-gains and punishers were point-losses. The results from Experiment 6 were mixed - some participants showed increased preference while others showed little change or a slight decrease. This appeared related to the order in which participants received the reinforcer-only and reinforcer + punisher conditions. Experiment 7 also found no consistent change in preference with increases in time-out durations. Instead, there was a slow increase in bias on the richer alternative across the eight sessions.
Overall, punishers had similar, but opposite, effects to reinforcers in detection procedures (Experiments 1, 2, & 3). These effects were successfully captured by Davison and Tustinís (1978) model of detection. The later experiments did not provide support for a subtractive model punishment model of choice, which had provided the best descriptor in corresponding concurrent-schedule research. Instead, Experiment 4 supported an additive model, and Experiments 5, 6, and 7 provided no evidence for either model - limitations and implications of these studies are discussed. However, the present thesis illustrates that the signal detection procedure is promising for studying the combined effects of reinforcement and punishment, and may offer a worthwhile complement to standard concurrent-schedule choice procedures.