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In Experiment I, 12 pigeons were given eight sessions of VI single stimulus training with a color in a particular context followed by eight sessions of similar training with a line angle in another context. On the next day, half of the subjects were tested for wavelength and angularity generalization in each of the two contexts, a procedure that was thus consistent with training for one dimension and inconsistent for the other. The subjects made significantly more responses to each training stimulus under the consistent context condition, but there was no difference in absolute or relative generalization slopes. In Experiment 2, 12 pigeons were trained as in Experiment I, but during generalization testing they were exposed to both contexts sequentially. Under the consistent context condition, the subjects responded more to the two training stimuli and yielded sharper absolute and relative wavelength generalization gradients: Under the inconsistent context condition, responding to the training wavelength was substantially disrupted. Thus, under appropriate testing conditions, contextual control over both the amount and the selectivity of responding can be demonstrated.Spear (1971, 1978) has proposed that success at retrieval of a memory is a function of the extent to which the subject notices, during retention testing, ambient contextual stimuli that were present but inconsequential to the target learning task and were stored as attributes of the target memory. The role of contextual retrieval cues in human memory has frequently been demonstrated. Rand and Wapner (1967) reported that the retention of a list of nonsense syllables was better when the subject was tested in the same postural position as during original learning (i.e., standing up or lying down). Greenspoon and Ranyard (1957) found that the color and location of the experimental room functioned as retrieval cues in a similar manner.A typical example from the animal memory literature is a proactive interference (PI) experiment reo ported by Spear (1971). Rats trained on a passive avoidance task followed by an active avoidance task typically showed recency in a delayed test, behaving in accordance with the active avoidance contingency.

Six experiments were performed in which pigeons were trained daily on a conditional serial discrimination reversal problem. In the standard training procedure, on odd-numbered days a vertical line was superimposed on a successive wavelength discrimination task. On even-numbered days a horizontal line was superimposed on the reverse wavelength discrimination task. Experiments 1, 2, and 3 assessed the degree of control acquired by the compound conditional cues (lines plus "days") and by the component elements (lines or "days"). Only those subjects that were trained with lines relevant mastered the reversal task. In testing, when the conditional line stimuli were present, they exerted strong control, and no days effect was noted. However, when tested in the absence of lines, those subjects that had had training with the compound conditional cue demonstrated reversal performance controlled by day, i.e., the pattern of alternating reversals had been acquired. Experiments 4, 5, and 6 tested alternate interpretations of the control exerted by the day cue. The results imply that explanations based on strict sequence learning, internal clocks, or interelement associations are untenable. Rather, it seems that the "potentiation" effect noted is due to separate storage of the wavelength discrimination problems and different retrieval processes elicited by presence versus absence of the line stimuli.

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