Transfer after pattern discrimination in primates

Abstract

Two squirrel monkeys and one infant orangutan were trained on a simultaneous discrimination be tween two stimuli that were identical except for a 90-deg difference in or ientation. Subsequent transfer tests failed to reveal reliably the positive and negative anomalous transfer effects, i.e., preference for a solid-line stimulus over the original positive stimulus in the same orientation and preference for the original negative stimulus over a solid-line stimulus in the same orientation, respectively. Different transfer test procedures were implicated as being responsible for this failure, and it was suggested that additional exploration of the various transfer test procedures should be pursued before the generality of the anomalous effects could be established. Dodwell (1970) and Dodwell , Litner , & Niemi (1970) recently replicated and extended the "anomalous transfer effect" first reported by Krechevsky (1938). Dodwell (1970) used hooded rats and squirrels and taught these Ss a simultaneous discrimination between the stimuli shown in Fig. l A, The training stimuli were four dashed lines in either a horizontal or vertical orientation, which he referred to as " rows" and " columns ," respectively. During subsequent transfer tests , Dodwell ( 1970) and Dodwell et al ( 1970) found a preference for four solid lines in the same orientation as the positive training stimulus over the positive training stimulus itself (see Fig. IB for an example). Further, they found a preference for the original negative training stimulus over four solid lines in the same orientation. These results are referred to as positive and negative anomalous transfer effects, respectively. In addition , when both stimuli were solid lines, Dodwell (1970) found a preference for the stimulus in the same orientation as the original positive training stimulus. Finally, when the original positive stimulus was shown along with a stimulus that had solid lines in the same orientation as the original negative stimulus , the original positive stimulus was preferred (Dodwell , 1970) . These results were taken as additional evidence tha t the anomalous effects are not simply a novelty effect.