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Publication Summary and Abstract

Prescott, T. J., Newton, L. D., Mir, N. U., and Parks, R. W. (2006), A new dissimilarity measure for finding semantic structure in category fluency data with implications for understanding memory organization in schizophrenia, Neuropsychology, 20:685-99.

Abstract. The ordering of words in category fluency lists is indicative of the semantic distance between items in conceptual memory. Several studies have concluded from structural analyses of such data, using cluster analysis or multidimensional scaling, that the semantic memory of patients with schizophrenia is more disorganized than that of controls. Previous studies have based their analyses on a measure of average inter-item dissimilarity devised by Chan et al. (1993). Here we derive a new and improved method of determining dissimilarity and show that when this measure is applied to the fluency lists of patients with schizophrenia the average pattern of organization for the animal category has similar structure to that of controls, but with greater variability between individuals.

December, 2007. Software available. The program Fluent, for calculation of matrices of normalised inter-item distances from raw verbal fluency data, using the mean cumulative frequency (mcf) measure is available below (freeware) in both PC and Mac versions.

June, 2009. Erratum. The analysis of variability report on p. 693 of the published article (p. 22 of the preprint) should have used the standard deviation of the mcf measure in place of the standard error. The corrected analysis (see attached file below) shows a similar result to the original one. For future between-group analyses of variability the standard deviation is recommended and is now automatically generated by the Fluent program (ver. 2). Thanks to Daniel Pratt for drawing my attention to this issue.

Article at APA online (publisher's website)

Correction to variability analysis
Fluent program for analysing semantic fluency data, version 2, for PC
Fluent program for analysing semantic fluency data, version 2, for MAC