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Tests of visuospatial memory following short (<1 s) and medium (1 to 30 s) delays have revealed characteristically different patterns of behavior in humans. These data have been interpreted as evidence for different memory systems operating during short (iconic memory) and long delays (working memory). Leising et al. (2019, Behavioural Processes, 169, Article 103957 ) found evidence for both systems in pigeons and humans completing a location change-detection task using a visual mask that disrupted accuracy following a short (100 ms), but not a long (1,000 ms) delay. Another common finding is that adding to-be-remembered items should disrupt accuracy after a long, but not short, delay. Experiments 1a and 1b reported this memory system crossover effect in pigeons and people, respectively, tested on location change detection with delays of 0, 100, and 1,000 ms and displays of two to 16 items. Experiments 2a and 2b reported that the color of the items had little (pigeons) or no (humans) effect on change-detection accuracy. Pigeons tested in Experiment 3 with longer delays (2,000, 4,000, and 8,000 ms) and large set sizes demonstrated the crossover effect with most displays but did not demonstrate an abrupt drop in accuracy characteristic of iconic memory. In Experiment 4, accuracy with novel types of change (color, shape, and size) was better after a 0-ms delay and above-chance levels on color and shape trials. These data demonstrate the memory system crossover effect in both humans and pigeons and expand our knowledge of the properties of memory systems across species.

A change in motivational state does not guarantee a change in operant behavior. Only after an organism has had contact with an outcome while in a relevant motivational state does behavior change, a phenomenon called incentive learning. While ample evidence indicates that this is true for primary reinforcers, it has not been established for conditioned reinforcers. We performed an experiment with rats where lever-presses were reinforced by presentations of an audiovisual stimulus that had previously preceded food delivery; in the critical experimental groups, the audiovisual stimulus was then paired a single time with a strong electric shock. Some animals were reexposed to the audiovisual stimulus. Lever-presses yielding no outcomes were recorded in a subsequent test. Animals that had been reexposed to the audiovisual stimulus after the aversive training responded less than did those that had not received reexposure. Indeed, those animals that were not re-exposed did not differ from a control group that received no aversive conditioning of the audiovisual stimulus. Moreover, these results were not mediated by a change in the food’s reinforcement value, but instead reflect a change in behavior with respect to the conditioned reinforcer itself. These are the first data to indicate that the affective value of conditioned stimuli, like that of unconditioned ones, is established when the organism comes into contact with them.