Multidimensional Representation of Decision-making in Chronic Schizophrenics.

We administered all paired comparisons of eight gambling stimuli to samples of inpatient schizophrenics, outpatient schizophrenics, and a comparison group of first-degree relatives. A matrix of pairwise preferences was elicited from each subject, and decomposed into a binary matrix indicating stimulus choice, and an unsigned dissimilarity matrix representing strength of preference. These matrices were analyzed using maximum likelihood multidimensional scaling methods, resulting in a representation of subjects and stimuli in an n-dimensional decision space. Results suggest that choice behavior of all groups was determined almost exclusively by the expected value of the stimuli, with no significant differences among the groups. Strength of preference was influenced by expected value for only the comparison group, with a much larger unsystematic component among the schizophrenic groups.