Progressive improvement in the learning of successive visual discrimination habits by rhesus monkeys and by human children (formation of "learning sets") has been described by Haiiow (4). These two primate species had markedly different pre-experimental histories; nevertheless, some of the characteristics of the performance measures were similar. Both showed gradual improvement in performance within each problem, and both showed gradual improvement from problem to problem. Subsequently Hayes, Thompson, and Hayes (7) reported that chimpanzees (Pan satyrus) also form learning sets, and with efficiency about equal to that of rhesus monkeys. The phenomenon has been reported also for three simian species: rhesus (Macaco, mulatto), squirrel monkey (Saimiri stiiirea), and marmoset (Callithrix jacchus) by Miles (12) and by Miles and Meyer (13); for cats by Warren and Baron (20); for rats by Koronakos and Arnold (11); for raccoons (Procyon lotor) by Shell and Riopelle (18) and by Johnson (9). Further data for rhesus monkeys have been reported by Braun (2) and by Riopelle ( 16).These investigations, some of which were conducted under substantially similar conditions, have shown that phyletic status is of importance in determining proficiency of performance despite the fact that any component discrimination problem.in the series would not successfully differentiate the species. Gardner and Nissen (3), for example, tested sheep, cows, horses, goats, chimpanzees, and human aments, and found comparable levels of performance in all species in a single discrimination problem. Clear differences among species were obtained for the multiple-discrimination task.Two factors, the success with which the
A significant development in the experimental study of the learning process during the past decade has been the demonstration by Harlow of progressive interproblem improvement in the rate of learning of visual discrimination problems by rhesus monkeys (formation of learning sets) (1), More recently it has been shown that learning sets develop at different rates in chimpanzees (3), platyrrhine monkeys (4, 8), marmosets (5), cats (9), and brain-injured rhesus monkeys (7, 10). The present study was designed to evaluate the performance of the American carnivore, the raccoon (Procyon lotor), in this learning situation.
METHOD
SubjectsFour young raccoons were tested. All were captured wild a few months before admission to the laboratory. Prior to the beginning of the experimental procedure the} 1 were permitted to become accustomed to the laboratory routine and were trained to displace a single test-object from a food well to secure reward.
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