Effects of Varying Stimulus Disparity and the Reinforcer Ratio in Concurrent‐schedule and Signal‐detection Procedures

Abstract

The present study measured the effects of stimulus and reinforcer variations on pigeons' behavior in two different choice procedures. Two intensities of white light were presented as the stimuli on the main key in a switching-key concurrent schedule and as the sample stimuli in a signal-detection procedure. Under both procedures, the scheduled rate of reinforcement was varied across conditions to produce various ratios of obtained reinforcement. These ratios were obtained for seven pairs of light intensities. In the concurrent schedules, the effects of reinforcer-ratio variations were positively correlated with the physical disparity between the two light intensities. In the signal-detection procedure, changes in the reinforcer ratio produced greater effects on performance when stimulus disparity was very low or very high compared to those found at intermediate levels of stimulus disparity. This discrepancy creates a dilemma for existing behavioral models of signal-detection performance.

Receiver operating characteristics from nonhuman animals: Some implications and directions for research with humans

“…The results from the high-response-disparity conditions are shown in Figure 9C. Although there were only two levels of stimulus disparity in this experiment, the pattern was consistent with the results of McCarthy and Davison (1984) and Alsop and Davison (1991). Overall, the criterion location measure ofbias does not provide an isobias measure for these sets of data.…”

“…Under these conditions, the payoff distribution is unlikely to be the same as the signal presentation probability. As the subject begins to show a response bias for the response alternative with a greater payoff rate (i.e.. that which is correct for the more frequently presented stimulus), the number of rewarded responses on that alternative should increase, whereas the number ofrewarded Davison's (1984) study, (8) the controlled payoff distribution procedure of McCarthy and Davison's (1984) study, and (C) the controlled payoff distribution procedure of Alsop and Davison's (1991) study. The triangles and squares show results from conditions with unequal payoff distributions; the circles show the results from conditions with equal frequencies of payoff across alternatives.…”

“…These results are supported by another large systematic study. Alsop and Davison (1991) arranged seven levels of stimulus disparity, and, at each level, they varied the controlled payoff distribution that the pigeons received across three conditions (.12, .50, and .88). Their group results ( Figure 8C) were similar to McCarthy and Davison's ( Figure 8B), albeit more variable, and they were more consistent with the pattern predicted by the criterion location measure ofbias because they failed to show the extreme deviations from the minor diagonal that are predicted by the likelihood ratio (Figure 1).…”

“…Figures 9A and 9B show a reanalysis of the data from McCarthy and Davison's (1984) and Alsop and Davison's (1991) "controlled" payoff distribution procedures ( Figures 8B and 8C). Estimates of sensitivity (d') and bias (c) for those conditions that arranged asymmetric payoff distributions were calculated and then plotted as a function of each other (the symmetric payoff distributions are uninformative for this analysis).2 If the criterion location describes an isobias function for these data, then there should be no systematic changes in response bias as sensitivity increases.…”

Quantitative Analyses of Matching‐to‐sample Performance

“…In addition, their point estimate of sample discriminability (log d) has been used extensively in models of performance in delayed MTS (DMTS) tasks where memorial processes are inferred because comparison stimuli are presented some time after the sample appeared (e.g., Harnett, McCarthy & Davison, 1984;White & McKenzie, 1982;White & Wixted, 1999). Davison and Tustin's model, however, makes a number of important assumptions that predict certain parameter invariances that have not always been supported by empirical research (see Alsop, 1991;Alsop & Davison, 1991;Davison & Nevin;Godfrey & Davison, 1999;Jones & White, 1992 for a discussion of these violations). A number of theoretical short-comings that limit the generality of the model have been identified as well (Alsop, 1991;Godfrey & Davison, 1998).…”