Visual comparison of random-dot patterns: Evidence concerning a fixed visual association between features and feature-relations

Abstract

Subjects made Same–-Different judgements on pairs of briefly presented random-dot patterns: they had to judge in separate experiments either whether the members of each pair were identical in shape or whether the number of dots in each pattern was the same. When one pattern was the rotated version of the other, the proportion of Same responses varied with the angle of rotation in the same way for the two types of judgement. From these and other data obtained with pattern pairs in which members differed in shape and in dot-number, the following inferences are made. First, in making both kinds of Same judgements, a fixed visual association is established between local features (dot-clusters within the pattern) and certain spatial relations between these local features. Thus when spatial-relation information is in principle irrelevant to the pattern-comparison task, as in judgements of dot-number, this information is not separated from the relevant local-feature information in the pattern representation. Second, in both tasks, a common description of the patterns in terms of local features and feature-relations is used in making a Same judgement. Third, some shape discrimination independent of orientation and some dot-number discrimination independent of shape are each the result of the process mediating Different decisions.