Observers' initial errors

Initial errors were the number of responses in the unreinforced direction made by an observer from the start of the first DR session for a problem until the first response was made in the reinforced direction. Preliminary inspection of the initial error data again revealed there to be a great deal of between subject variability, and one observer, assigned to Group DIFF, was found to have contributed two of the three most unusual observations (Zs = 4.09, 3.40). This rat was excluded from subsequent analyses of initial errors.

‘^Similar results occurred when reversal 7 (the final problem in which the reinforced direction was the same as that reinforced during the transfer test) was used as the baseline instead of reversal 8.

Figure 6.7: Mean initial errors (number of responses in the unreinforced direction until the first response in the reinforced direction) per reversal for each acquisiton group from Experim ent 9. During Reversal 9, the transfer problem, contingencies were switched for Groups SAME and DIFF. "SAME", observers rewarded for making the same responses as their demonstrators; "DIFF", observers rewarded for making a different response to that of their demonstrators; "RAND", reinforced direction was not contingent upon the direction of demonstrators' responding.

I

Figure 6.7 displays group-mean initial errors per reversal for each o f the groups, with levels of the counterbalancing variable collapsed and data from the outlier observer excluded. Figure 6.7 indicates that, during acquisition training, there was substantial variance in mean initial errors, and no clear pattern of differences. A comparison o f the group-mean initial errors per reversal during the transfer problem with those at the end o f training indicated that the differences were not in the expected direction. The transfer problem appeared to result in an increase for Group RAND only, and a decrease for the only two treatments (SAME and DIFF) for which an increase was predicted.

The initial error data were subjected to two ANOVAs. To examine acquisition performance, initial errors were subjected to a three factor mixed ANOVA of acquisition group x initial direction reinforced x reversal. This revealed no statistically significant differences for any factor (reversal, F(7,105) = 1.62, p = .1375, acquisition group, F(2,15) = 1.50, p = .2545, initial direction reinforced, F < 1), or interaction between factors. Thus, this analysis o f initial error data provided no evidence for an improvement in performance at the beginning of training problems across reversals, nor evidence to suggest that observers were sensitive to the correspondence between observed responses and those that they themselves executed.

In order to examine transfer performance, initial errors were subjected to a three factor mixed ANOVA o f acquisition group x initial direction reinforced x reversal, where the reversal factor included data from the transfer problem, and the eighth problem as a baseline. This revealed a statistically significant difference between acquisition groups, F(2,15) = 3.78, p = .0469, but not for either of the other factors, Fs < 1. Re-examination of Figure 6.7 suggests that the reliable acquisition group effect is likely to be due to between group variance in initial errors per reversal during the eighth problem rather that at transfer, an interpretation which received some support from the fact that the only interaction which approached statistical significance was that between acquisition group and reversal, F(2, 15) = 3.59, p = .0533. In order to examine potential group differences in the magnitude and direction in shift in initial errors from baseline to transfer, this marginally reliable interaction was examined further with simple effects. A tendency for a difference in the number of initial errors made on the test and eighth reversal problems was not found for any o f the acquisition groups (Group SAME, F < 1, Group DIFF, F (l,6 ) = 1.93, p = .2140, Group RAND, F (l,7 ) = 4.53, p = .0709).

G

D

N either Experiment 8 nor Experiment 9 produced any evidence to suggest that observers' direction of responding was influenced by the demonstration sessions to which they had been exposed. There was no evidence of an untrained sensitivity to the correspondence between observed and executed responses, which could have been indicated if the performance of Group SAME improved faster during training than that of Group DIFF. Although, in both Experiment 8 and Experiment 9, evidence was found for a reduction in total errors across reversals, the rate at which these errors declined was not found to be dependent upon acquisition group membership in either experiment. Initial errors per reversal made during acquisition training were not found to change across reversals in any way in either experiment. Therefore, no evidence was found to suggest that the type o f procedure used in the experiments reported in this chapter is likely to provide an especially sensitive test of whether rats exhibit an untrained tendency to be influenced, by some aspect o f demonstration sessions to which they were exposed, to respond in the same direction as that o f their demonstrator.

Furthermore, neither experiment generated findings to suggest that a demonstrator-consistent responding effect had been acquired as a result of conditional discrimination training. Such a putative demonstrator-consistent responding effect was assessed by transfer performance when the relationship between the observed and reinforced direction o f responding was manipulated, either between subjects (Experiment 8), or within subjects (Experiment 9). In neither experiment did a contingency switch result in an increase in either initial, or total, errors. This failure to find evidence that rats can be trained to respond conditionally upon some aspect of their demonstration sessions might suggest that a training-to-imitate approach is not suited to the investigation of imitation in rats using a bidirectional control procedure. The remainder of this discussion will focus on potential reasons for this failure because the primary motivation behind the design of the present experiments was the belief that training studies might produce a demonstrator-consistent responding effect of sufficient replicability to be exploited in future experiments.

The failure to find a demonstrator consistent responding effect on a transfer test which followed conditional discrimination training in either of the experiments reported in the present chapter might be due to several reasons. One possibility, which can be discounted, is that it is due to rats' insensitivity to the correspondence between observed and executed actions. A representation, in a form which is compatible with the control of action, of dem onstrated actions is one form of information that observers may potentially be able to extract from demonstration sessions. However, this is not the only type o f information that the observers may have been able to extract from a demonstration session and use as a conditional cue. Other types of information include: the identity of the demonstrator (different demonstrators were observed to respond to the right, and to the left), the direction in which the joystick moved across an observer's visual field, and any physical traces deposited during the demonstration session. Demonstrator-consistent responding effects that have been demonstrated in standard NDR tests of imitation using a bidirectional control (see Chapters 2 and 5 for reviews) provide evidence that observers' directional responding can be influenced by some aspect of a demonstration session.

A nother possibility is that the information provided by demonstration sessions associated with left and right demonstrator responses was not salient enough, or did not have the required properties, to act as a cue to influence conditional responding. Following this position, a training approach would be unlikely to prove useful for the investigation of imitation using rat subjects and a bidirectional control procedure. Again, the findings of the present experiments do not provide convincing evidence to support this position. Few of the procedural parameters which might be manipulated were explored in these experiments, so the procedures which were employed might have failed to present observers with conditions ideal for the extraction of a conditional cue, from their demonstration sessions, that might influence their directional responding. Furthermore, the relatively long DR sessions given to observers in both experiments may have reduced the likelihood that any detected conditional cue would be used by the observers; the hungry observers could obtain a reasonable quantity of food during each training session even if their behaviour was not influenced by a cue. Perhaps if a training-to-imitate approach is to be effectively applied to a bidirectional control method, shorter differential reinforcement sessions should be used (and more problems) thus modelling more closely the procedure used in maze running experiments.

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