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After rats were conditioned to prefer a flavor (CS+) paired with sucrose over another flavor (CS−) paired with saccharin, this conditioned flavor preference was extinguished by presenting the CS+ flavor without sucrose. These results were replicated in a second experiment in which spontaneous recovery of the extinguished flavor preference was demonstrated 7, 14, and 21 days after the extinction test. This is the first clear demonstration of the extinction and spontaneous recovery of a conditioned flavor preference based on calories. The implications of these results for our understanding of the mechanism underlying the conditioning of flavor preferences are explored.

In the present study, we investigated the mechanisms of potentiation using pigeons as subjects. Half the groups were given unreinforced preexposures to the CS on 2 consecutive days before aversion training. After training, the taste aversion was extinguished in some of the groups conditioned with a colored, tasty compound. Postconditioning extinction of the taste aversion was found to attenuate potentiated color aversions. This was the case for the subjects that both were and were not preexposed to the CS. These results lend support to the summation theory of potentiation (Durlach & Rescorla, 1980) and weaken the claim that CS preexposures are necessary for obtaining such support. Alternative accounts of the data are discussed.

Rajan Mahadevan has an exceptional memory for digits. A series of experiments using memory span and number matrices show that, consistent with the account of skilled memory given by Chase and Ericsson (1982, in G. H. Bower (Ed.), in The psychology of learning and motivation, Vol. 16 (pp. 1–58). New York: Academic Press), Rajan uses a retrieval structure and demonstrates a reduction in study time with practice. However, contrary to the Chase and Ericsson theory, Rajan uses a modified paired-associate procedure rather than using pre-existing knowledge to encode the presented information. These data suggest that Rajan is quite different from other memorists but shows comparable levels of performance.

Golden hamsters (Mesocricetus auratus) and dwarf hamsters (Phodopus campbelli) interacted with a conspecific demonstrator that had recently consumed a flavored food. When given a choice between their demonstrator's flavor and another flavor, the dwarf hamsters preferred the flavor their demonstrator had eaten. Golden hamsters did not prefer their demonstrators' diets when the demonstrators were unrelated adults or littermates, but they did when the demonstrator was their mother. Videotaping the interactions between demonstrators and observers revealed that adult golden hamsters did not investigate foods hoarded by their demonstrators whereas dwarf hamsters did. These results are interpreted in terms of the stimuli that activate feeding behavior systems in these 2 hamster species.

Bobwhites (Colinus virginianus) were trained to peck a green lighted key to receive food. Bird response performance was monitored for 14 days, then birds were dosed with five levels of dieldrin (50 to 300 micrograms every other day) for 42 days while their response performance was monitored. At the end of the 42-day dosage period, mean brain concentrations of dieldrin ranged from 2.6 ppm to 11.8 ppm; lower concentrations associated with lower dosage levels. All dieldrin dosage levels altered cage behavior of bobwhites, dieldrin dosage levels greater than 100 micrograms resulted in slower and less accurate responses by dosed birds during the 42-day trial period.

Following key peck training to a chromatic stimulus, one group of pigeons was given CER training with a white vertical line superimposed on the key as the CS and shock as the US; a second group was given presentations of the CS only; a third group received shock only with no CS preceding it on the key; a fourth group received only the key peck training with the chromatic stimulus. All groups then received identical training on a successive operant discrimination involving auditory stimuli. The CER subjects learned this discrimination faster than did subjects in the other three groups, which did not differ. The results extend the generality of conditions which facilitate the acquisition of successive operant discriminations.

Pigeons were given errorless discrimination training between chromatic stimuli with a specific reinforced response associated with each discriminative stimulus. These S s subsequently acquired a successive go/no-go auditory discrimination (utilizing one response class) faster than S s given single stimulus training. These results are more compatible with an explanation of transfer of training in successive operant discrimination learning based on general attention than one based on withholding responses.

Ten pigeons were given VI 2-min single-stimulus training and then were switched to a chain VI hmin VI 1-min schedule. For half of the Ss, the original training stimulus became the stimulus closest to primary reinforcement (S1) and a new stimulus became the stimulus farthest from primary reinforcement (S2). For the other Ss, the training stimulus became S2 and the new stimulus became S2. After 51/2h of training on the chained schedule, a generalization test in extinction revealed peak shifts away from S2 beyond S1 in both groups.