Associative processes in differential outcome discriminations.

This study assessed the role of stimulus–outcome (S–O) and response–outcome (R–O) associations in differential outcome performances. In Experiment 1, pigeons learned one-to-many matching-to-sample with differential R–O associations but with either differential or nondifferential sample-outcome (S–O) associations. Later, both groups showed strong transfer of matching to novel samples that were differentially associated with the same outcomes used in training. Experiment 2 reversed the training conditions for each group. The switch from differential to nondifferential S–O associations produced a large drop in matching accuracy, whereas the opposite switch had only a small effect. Following recovery, both groups again showed positive transfer to novel samples, although transfer was stronger following differential S–O training. These data support a 2-process ("outcome expectancy") account of differential outcome performances but also indicate a contribution of bidirectional R–O associations. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Enhancement of matching acquisition by differential comparison-outcome associations.

Two experiments investigated whether differential outcomes in matching-to-sample (MTS) would enhance acquisition even in cases in which the outcomes could not be anticipated at the beginning of a trial. In Exp 1, food and no-food outcomes were differential with respect to both hue and line comparisons in one-to-many MTS but were nondifferential with respect to samples. Overall acquisition and acquisition with each comparison set were faster in relation to controls that received each outcome equally often on all trials. In Exp 2, hue and line comparisons were associated with either different probabilities of food (p?=?1.0 vs 0.2) or with the same probability (p?=?.6). Again, matching acquisition was more rapid in the differential group. These data demonstrate that differential comparison-outcome associations are sufficient to enhance conditional discrimination learning. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Further tests of response–outcome associations in differential-outcome matching-to-sample.

Two transfer-of-control experiments assessed pigeons' sensitivity to response-outcome associations in differential-outcome discriminations. In Experiment 1, pigeons were trained on one-to-many matching-to-sample with food and no-food outcomes that were differential or nondifferential with respect to correct choice. The samples were then replaced by novel stimuli that had differential or nondifferential associations with those same outcomes. Transfer of matching occurred only when the novel samples and their respective choice responses had identical differential-outcome associations. Experiment 2 showed that the outcomes themselves were effective samples if the choices they cued yielded those outcomes in training. These data provide further evidence that the relations between comparison choice and consequent outcomes influences pigeons' matching performances. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Retrospective coding in pigeons' delayed matching-to-sample.

In Exp I, 2 groups of 6 White Carneaux pigeons initially learned 0-delay matching-to-sample with identical comparison stimuli (vertical and horizontal lines) but with different sample stimuli (red and green hues or vertical and horizontal lines). Longer delays were then introduced between sample offset and comparison onset to assess whether Ss were prospectively coding the same events (the correct line comparisons) or retrospectively coding different events (their respective sample stimuli). The hue-sample group matched more accurately and showed a slower rate of forgetting than the line-sample group. In Exp II, 20 mixed-breed pigeons were trained (1) with either hues or lines as both sample and comparison stimuli or (2) with hue samples and line comparisons or vice versa. Subsequent delay tests revealed that the hue-sample groups remembered more accurately and generally showed slower rates of forgetting than the line-sample groups. Comparison dimension had little or no effect on performance. Data suggest that pigeons retrospectively code the samples in delayed matching-to-sample. (27 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)