Data from recent studies of pigeon short-term memory were considered in relation to two theoretical issues. The first concerned the question of whether short-term information processing in the pigeon is better characterized as an active or passive process. Research on retroactive interference, sample surprisingness, and stimulus control of forgetting provides considerable support for the hypothesis that pigeons actively process or rehearse information in contemporary short-term memory preparations.

A second issue concerned the nature of encoding in pigeon short-term memory. The specific question considered was whether memories correspond to an isomorphic representation of the sample or whether the pigeon remembers an instruction or disposition to respond. A considerable body of circumstantial evidence in favor of an instructional hypothesis has been generated by recent studies on retention and transfer in the advance key procedure and by studies on interference, sample repetition, and sample compounding in delayed matching. The most direct evidence in support of the idea that the pigeon remembers "what to do" rather than "what happened" comes from research in which the types of errors committed were analyzed. This work has shown that the majority of errors can be traced to confusions among similar choice stimuli rather than among similar sample stimuli.

To organize and account for these and other findings on pigeon short-term memory, a general theoretical viewpoint was offered. The model maintains a fundamental distinction between active and passive memories and places heavy emphasis on processes of rehearsal in maintaining memories in the active state. According to this view, a memory must be in an active state in order for that memory to exert control over behavior. To-be-remembered events are viewed as temporarily activating long-term instructional representations in an all-or-none fashion. The probability with which a stimulus event activates its associated long-term representation is dependent on the relative discriminability of that stimulus event. Processes of maintenance rehearsal serve to increase the temporal duration of memory activation following offset of the stimulus originally giving rise to the activation. Some of the salient properties of the rehearsal process include: (a) variable intensity, duration, and efficiency, all of which are subject to practice effects; (b) control of rehearsal termination by environmental events; and (c) a relation to memory content such that the efficiency with which rehearsal either occurs or is terminated is related inversely to the complexity of memorial content.