Do conditional reinforcers count?

Abstract

Six pigeons were trained on a procedure in which seven components arranged different food-delivery ratios on concurrent variable-interval schedules each session. The components were unsignaled, lasted for 10 food deliveries, and occurred in random order with a 60-s blackout between components. The schedules were arranged using a switching-key procedure in which two responses on a center key changed the schedules and associated stimuli on two side keys. In Experiment 1, over five conditions, an increasing proportion of food deliveries accompanied by a magazine light was replaced with the presentation of the magazine light only. Local analyses of preference showed preference pulses toward the alternative that had just produced either a food-plus-magazine-light or magazine-light-only presentation, but pulses after food deliveries were always greater than those after magazine lights. Increasing proportions of magazine lights did not change the size of preference pulses after food or magazine-light presentations. Experiment 2 investigated the effects of correlations between food ratios and magazine-light ratios: In Condition 6, magazine-light ratios in components were inversely correlated (-1.0) with food ratios, and in Condition 7, magazine-light ratios were uncorrelated with food ratios. In Conditions 8 and 9, pecks also produced occasional 2.5-s flashes of a green keylight. In Condition 8, food and magazine-light ratios were correlated 1.0 whereas food and green-key ratios were correlated -1.0. In Condition 9, food and green-key ratios were correlated 1.0 whereas food and magazine-light ratios were correlated -1.0. Preference pulses toward alternatives after magazine lights and green keys depended on the correlation between these event ratios and the food ratios: If the ratios were correlated +1.0, positive preference pulses resulted; if the correlation was -1.0, preference pulses were negative. These results suggest that the Law of Effect has more to do with events signaling consequences than with strengthening responses.

Fig 1. Sensitivity to food ratio and bias (a and log c, respectively, in Equation 1) prior to each successive food delivery in components in Condition 1.

The data used were numbers of responses between food presentations averaged across the 6 pigeons. Data for individual pigeons are shown in Appendix Figure 1.

Fig 2. Upper panel: Log left/right-key response ratios for the first 40 responses following left- and right-key food deliveries in Condition 1.

The data were averaged across the 6 pigeons. The horizontal line shows the overall log response ratio in this condition. Lower panel: The same data collapsed and plotted as log response ratios to the alternative that just produced food plus magazine light presentations (log P/N). Results for individual pigeons are shown in Appendix Figure 2.

Fig 3. Values of sensitivity to food ratio and bias (a and log c, respectively, in Equation 1) prior to each successive food plus magazine light or magazine-light-only presentation across the seven components as the proportion of magazine lights to total events was increased.

Food (F) and magazine light (ML) refer to food plus magazine light and magazine-light-only presentations, respectively: Thus, in Condition 2, for example, we arranged 10 food deliveries and two magazine-light deliveries per component (10 F + 2 ML). The data used were numbers of responses between food presentations averaged across the 6 pigeons in Conditions 1 to 5. The lower-right graph shows mean sensitivity and bias values across Conditions 1 to 5, and mean values for each condition, for comparison purposes.

Fig 4. Response ratios to the alternative that just produced food plus magazine light or magazine-light-only presentations (log P/N) for the first 40 responses following left- and right-key events as the proportion of magazine-light-only presentations to total events was increased.

The upper graph shows performance after food plus magazine light presentations; the lower graph shows performance after magazine-light-only presentations. The data were averaged across the 6 pigeons in Conditions 1 to 5. C refers to the experimental condition, F to food plus magazine light presentations, and ML to magazine-light-only presentations.

Fig 5. Log P/N response ratios for the first 40 responses following food plus magazine light presentations and magazine-light-only presentations in conditions when the magazine-light ratio was positively correlated with the food ratio (Condition 5, left panel), when the magazine-light ratio was negatively correlated with the food ratio (Condition 6, center panel), and when the magazine-light ratio was uncorrelated with the food ratio (Condition 7, right panel).

The data were averaged across the 6 pigeons.

Fig 6. Conditions 8 and 9.

Log P/N response ratios following food, magazine-light only, or a green keylight for the subsequent 40 responses. The upper panel (Condition 8) shows performance when the magazine-light ratio was correlated +1.0 with the food ratio, and the green-keylight ratio was correlated −1.0 with the food ratio. The lower panel (Condition 9) shows performance when the magazine-light ratio was correlated −1.0 with the food ratio and the green-keylight ratio was correlated +1.0 with the food ratio. The data were averaged across the 6 pigeons.

Fig 7. Log P/N response ratio following food plus magazine light, magazine- light-only, or green-keylight presentations for the first 10 responses as a function of increasing number of these events within components.

Results are shown separately for Conditions 8 and 9, which reversed the correlations between magazine-light ratio and food ratio, and green-keylight ratio and food ratio. The symbols distinguish the 10 responses.

Fig A1. Values of sensitivity to food ratio and bias (a and log c, respectively, in Equation 1) prior to each successive food delivery in components for each individual subject in Condition 1.

Fig A2. Log P/N response ratios to the alternative that just produced food plus magazine light presentations for the first 40 responses following food delivery in Condition 1 for each individual subject.