Stimulus disparity and punisher control of human signal-detection performance

Abstract

The present experiment examined the effects of varying stimulus disparity and relative punisher frequencies on signal detection by humans. Participants were placed into one of two groups. Group 3 participants were presented with 1:3 and 3:1 punisher frequency ratios, while Group 11 participants were presented with 1:11 and 11:1 punisher frequency ratios. For both groups, stimulus disparity was varied across three levels (low, medium, high) for each punisher ratio. In all conditions, correct responses were intermittently reinforced (1:1 reinforcer frequency ratio). Participants were mostly biased away from the more punished alternative, with more extreme response biases found for Group 11 participants compared to Group 3. For both groups, estimates of discriminability increased systematically across the three disparity levels and were unaffected by the punisher ratios. Likewise, estimates of response bias and sensitivity to the punisher ratios were unaffected by changes in discriminability, supporting the assumption of parameter invariance in the Davison and Tustin (1978) model of signal detection. Overall, the present experiment found no relation between stimulus control and punisher control, and provided further evidence for similar but opposite effects of punishers to reinforcers in signal-detection procedures.

Keywords: human; mouse-click; point-loss; punishment; response bias; signal detection; stimulus disparity.

Fig 1

Sensitivity of response bias to changes in reinforcer ratio (a) plotted against estimates of discriminability (log d) for individual subjects from three previous studies: McCarthy and Davison (1984—top), Alsop and Davison (1991—middle), and Alsop and Porritt (2006—bottom). See text for details.

Fig 2

Mean discriminability (log d—top) and response bias (log b—bottom) for each stimulus disparity level calculated across participants in the 1:4 reinforcer ratio group (black bars) and 4:1 reinforcer ratio group (grey bars) in Johnstone and Alsop's (2000) study.

Fig 3

Mean discriminability (log d—top) and response bias (log b—bottom) for each stimulus disparity level calculated across all participants in Group 3 (left) and Group 11 (right).

Fig 4

Individual estimates of response bias (log b) for the 1:11 (left) and 11:1 (right) arranged punisher ratios at each stimulus disparity level for participants in Group 11.

Fig 5

Individual estimates of sensitivity to changes in punisher ratio (a_p) are plotted as a function of discriminability (log d) for each participant in Group 3 (left) and Group 11 (right).