Uniting Identification, Similarity and Preference: General Recognition Theory
Nancy A. Perrin Portland State University
Psychology has a long history of investigating identification, similarity, and preference judgments. However, until recently no theory attempted to account for all three of these judgments simultaneously, despite the fact that they appear to be strongly related. For example, in making a preference judgment the items in the choice set may first be identified, next the similarity between the different items in the choice set might be estimated, and finally preference can be determined. In 1986, General Recognition Theory (GRT) ( Ashby & Perrin, 1988; Ashby & Townsend, 1986; Perrin, 1986) was introduced. One of the strengths of this theory is that it attempts to unify research in identification, similarity, and preference by using a common psychological space to model all three types of responses. Therefore, GRT offers a framework to better understand the perceptual processes associated with these judgments.
In an identification experiment, the stimulus set consists of two or more stimuli, and the subject is shown a stimulus and asked to name or identify it. Feedback as to the correct response is often given. Each stimulus is presented many times, and a confusion matrix is used to summarize the responses. The elements of the matrix are the number of times the column stimulus was identified as the row stimulus. In a similarity experiment, subjects are shown two stimuli simultaneously or consecutively and are asked to judge the similarity or dissimilarity of the stimuli. Subjects are shown all possible pairs of the stimuli, and the response scale for the similarity judgment is typically a rating scale. The responses are summarized in a similarity matrix, with each element representing the judged similarity of the row and column stimuli. Finally, in a preference experiment, subjects are asked to select the stimulus they most prefer. The most common preference experiment involves paired comparisons in which subjects