Semantic distance and single cue use in category search

Perceptual classification may be based either on the physical features of target and background items or on the semantic attributes of the presented items. In this paper we used enumeration tasks to study the role of semantic features in a categorial classification task. This means that subjects were asked to count the number of target words in a display belonging to one semantic category among a number of background items of other categories. Our goal was to study the decision logic in category search by manipulating target background conditions and the semantic distance between target and background classes. In the first experiment we found that the larger the semantic distance between targets and background words, the easier it was to find the targets. In the second experiment we found a "pop-out" effect, in which subjects could use and benefit from a single distinctive semantic feature, "part-likeness", in categorial classification. The results of the two experiments imply that the categorization decision logic is basically the same in physical and semantic perceptual classification.