Variables underlying the recognition of random shapes

Speed of sorting decks of 32 cards with two alternative stimuli was measured. The stimuli were pairs of dots with attributes of distance between dots, angle of orientation of the pair, and position of the pair to the right or left of center. The attributes varied in relative discriminability and were used in all possible pair- and triple-correlated (redundant) combinations. Results showed an increase in speed of sorting with either an increase in discriminability or an increase in number of redundant attributes. It is argued that the increased speed with addition of redundant attributes is due both to a selective serial processing of attributes (requiring attribute separability) and to an increased discriminability with combined attributes (requiring attribute integrality).     

Verbal interference in a perceptual comparison task

When Ss had to indicate if the colors of pairs of items from the Stroop test were the same or different, the usual interference effect was completely eliminated. However, when the verbal information consisted of SAME and DIFF rather than color names, interference was reestablished. This indicates that the perceptual comparison task does not eliminate interference simply by rendering Ss insensitive to the meanings of words.     

The uniqueness and significance of simple structure demonstrated by contrasting organic “natural structure” and “random structure” data

The study compares the extent to which naturally structured data and artificial, relatively random data (both with the same basic parameters) produce simple structure factors which are uniquely determined. Two examples of unstructured matrices were compared with the ball problem matrix. The results show that an oblique position of maximum hyperplane count in the structured data differs from that in the unstructured by reaching a significantly more unique position in terms of the exactitude with which it is re-discoverable when starting from different positions, and by reaching (at the maximum) a significantly higher hyperplane count.     

A note on chaining and temporal discrimination

Four pigeons were exposed to a two-key DRL procedure. At the start of a trial, key A was illuminated. A response to the lighted key turned it off and simultaneously illuminated key B. Reinforcement was available for responses on key B which followed the initial key A response by more than 2 sec. In the course of exposure to these conditions, all birds acquired superstitious response chains on key A. The distribution of the number of responses on key A preceding a key B response and the distribution of intervals elapsing from the initial key A response to the key B response were of the same form. The suggestion is made that the superstitious responding on key A served to mediate the required delay interval. However, when intervals between successive key A responses were recorded for one subject, they were found to be regularly spaced in time. Thus, the problem remains of how this behavior is itself timed.     

Effects of deprivation and reinforcement-magnitude on response variability

Animals were trained to displace any one of five response keys in order to put themselves in a stimulus condition in which reinforcement could be obtained by depressing a response lever. Decreased deprivation and magnitude of reinforcement were found to increase the variability of the distribution of key responses. The relevance of these findings to other experiments in which deprivation, reinforcement magnitude, and intermittent reinforcement were studied is discussed.