Four studies are reported examining the development of spontaneous alternation behavior in rats. Spontaneous alternation was found to increase from a rate of around 20% in 15-16 day old rats to around 90% in 100-day olds. Increasing the length of confinement in the 1st chosen goal arm did not affect alternation rates. Spontaneous alternation could be disrupted or facilitated in mature animals by the administration of either scopolamine hydrobromide or physostigmine sulphate, drugs which had no effect on the typical alternation pattern of 16-day olds, but appeared to begin to have an effect at around 24 days. Dose response curves revealed certain age-dose level interactions which were consistent with the hypothesis that cholinergic inhibitory mechanisms in the brain develop gradually in the rat.

Three groups of 8 male albino rats within each of the age ranges 24, 50, and 100 days were trained on an active avoidance task to a criterion of 10 successive avoidances. The number of trials to criterion was found to be a monotonic function of age. One group at each age was tested immediately thereafter for passive avoidance of the conditioning chamber, another group was tested for passive avoidance after 25 days, and the third was tested for retention of active avoidance after 25 days. Groups at 50, 75, and 125 days were used as controls for the active avoidance retention groups. All animals took significantly fewer trials to relearn the active avoidance after 25 days than did controls on the acquisition of the original learning task. On passive avoidance 24‐day olds performed less efficiently than the older groups and failed to show any retention after 25 days.

Males of Nippostrongylus brasiliensis, an intestinal parasite of rodents, were maintained in an environment permeated with pheromone produced by females of the species. After the males were removed from that environment, their subsequent ability to orient to a gradient of the pheromone emanating from living females was greatly reduced for periods up to 2 hours. This phenomenon might serve as the basis for a new, selective antihelminthic technique in which the premating communication between males and females is disrupted.

The learning of multiple choice discrimination tasks of 3-, 4-, 5-, and 6-year-old children was compared using the components of learning of cue significance and response regulation. No significant differences between age groups were found in the occurrence of cue significance learning, although the younger children's cue significance responses were less accurately related to task solution. On the two easier tasks, the component of response regulation improved significantly over the age range of 3-5 years. On the two more difficult tasks 6-year-olds' response regulation was significantly better than that of 4- and 5-year-olds. In a second experiment involving two different training procedures, 5-year-olds performed better than 4-year-olds. Only for 5-year-olds was performance with the procedure emphasizing response regulation superior to performance with the procedure emphasizing cue significance. These results are discussed in terms of an association between development of response regulation and maturation of hippocampal-prefrontal cortex systems.

rabbits, 8 cats and 7 of 8 rats mastered double alternation problem on the WGTA to the criterion of 80% correct responses over 50 consecutive sequences of responses; rats required many more trials (520-700 response sequences) than did the rabbits (180-420 sequences) or cats (150-360 sequences). Despite the fact that learning proceeded much more slowly for the rats, a striking similarity in pattern of learning to that of rabbits and eats was evidenced, thus, differing from results described by other workers for cats. Differences in procedure that may have accounted for these differing results for cats were outlined.