Value transfer in simultaneous object discriminations by rats

Abstract

) with pigeons trained on two concurrent simultaneous color discriminations (A1B , C1D ) in which the probability of reinforcement for responding to A was greater than that for responding to C. When the birds were tested for their B versus D preferences, they consistently chose B, the stimulus paired with the more positive A, over D, the stimulus paired with the less positive C. This effect was observed whether A was made more positive within the A1B and C1D discrimination context (Zentall & Sherburne, 1994;Zentall et al., 1996, Experiments 1 and 2) or on off-baseline trials (Dorrance et al., 1998; Zentall et al., 1996, Experiment 3). Dorrance et al. noted that this effect is contrary to the occasion-setting hypothesis, which predicts that birds should avoid B (and thus choose D) because the former had come to signal a decrease in reinforcement to its associated A stimulus.Aitken (1999) reanalyzed Dorrance et al.'s (1998) data to argue that the pigeons' preferences for B over D could have resulted from the development of greater conditioned inhibition to D than to B during initial discrimination training. Aitken (1999, see Figure 1, p. 292) found a strong direct relationship (r 2 5 .93) between B preference on BD tests and overall errors to D during discrimination training. It is noteworthy that Dorrance et al. found that their birds consistently made more errors to D than to B during training, except in Experiment 3, where their birds failed to reliably prefer B to D. Although they reported a nonsignificant difference between B and D errors in their second experiment, 6 of their 8 pigeons made more D than B errors, 1 showed the same number of errors, and another made more errors to B than to D. Analysis of these data by a Wilcoxon test revealed significantlymore D than B errors (T 5 5.5, p , .05, one-tailed). Earlier studies from their laboratory (Zentall & Sherburne, 1994;Zentall et al., 1996, Experiment 1) also reported tendencies, albeit nonsignificant ones, for more D than B errors.Notwithstanding Zentall, Dorrance, and Clement's (1999) reply to Aitken (1999), we believe that differential experiences with the negative stimuli during training must Value transfer in simultaneous object discriminations by rats JEROME S. COHEN, CHRISTINE DRUMMOND, and NICOLE TERRELONGE University of Windsor, Windsor, Ontario, Canada Increasing the amount of sunflower seeds under a baited object when it occurs either within or external to a simultaneous object discrimination increases the value transferred to the nonbaited object. Rats were trained with two object discriminations, A 1 B 0 and C 1 D 0 , where the superscript refers to the number of sunflower seeds obtained for pushing aside the object. The amount under A was increased to six on other trials in which the A 6 or C 1 object alternated with regular A 1 B 0 or C 1 D 0 discrimination trials. The A and C objects on the alternating trials were presented alone (Experiment 1), with a common nonbaited object (A 6 X 0 and C 1 X 0 ; Experiments 2 and 3), or with two diffe...

Integration and representation in rats’ serial pattern learning in the T-maze

“…Constant, Quebec, served in this experiment. They were veterans of an earlier simultaneous object discrimination study in a different object-choice apparatus (Cohen, Drummond, & Terrelonge, 2001), were approximately 150 days old, and weighed over 450 g at the start of this experiment. The same general maintenance and housing conditions as those in Cohen, Westlake, and Pepin (2001) remained in effect.…”