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Len Horowitz

Professor / Emeritus
Primary Area: 
Office Location: 
Jordan Hall, Building 420
(650) 725-5699
Roz Grayson

Research Summary

My research focuses on interpersonal processes related to personality and psychopathology.  Our interpersonal model of dyadic interaction emphasizes the motives that energize interpersonal behavior and the behavioral ambiguity that arises if the interpersonal motive is unclear.  The model organizes interpersonal motives broadly into two abstract categories—communion (concerning connections between people) and agency (concerning the influence of each person upon the other).  Communion and agency may also be viewed as dimensions along which interpersonal motives may each be located.  Adult attachment styles are related to these two dimensions, and much of our work relates to attachment styles.  The model also classifies and clarifies interpersonal problems and personality disorders, which we also study.  Finally, we are interested in individual differences in the kind of knowledge that a person must possess in order to satisfy a particular interpersonal motive, and we have developed laboratory procedures for assessing cognitive structures that are relevant to particular interpersonal motives.


The Johns Hopkins University (1960). Psychology

Courses Taught

Special Topics in Personality and Psychopathology (seminar)
Interpersonal Basis of Abnormal Psychology (undergraduate course)
Personality and Psychopathology (graduate course)

Other Biographical Information

Leonard M. Horowitz has been a Woodrow Wilson Fellow, a Social Science Research Council Fellow, and a Fulbright Fellow at University College, University of London.  He received his clinical training at the Mt. Zion Psychiatric Clinic as a Special Fellow of the National Institute of Mental Health, and he received a James McKeen Cattell Award in 1986-1987.  He has been a panelist of the National Science Foundation and served on a number of ad hoc committees for the National Institute of Mental Health as well as on advisory boards of numerous journals.  Together with Hans Strupp and Michael Lambert, he directed an American Psychological Association Task Force on creating a core battery of standardized tests for evaluating the outcome of psychotherapy.  That work resulted in the book Measuring Patient Changes in Mood, Anxiety, and Personality Disorders:  Toward a Core Battery (APA, 1997).  His test, the Inventory of Interpersonal Problems, was published in 2000 by the Psychological Corporation. His book Interpersonal Foundations of Psychopathology was published in 2004. He was president of the Society for Psychotherapy Research from 1992 to 1993 and president of the Society for Interpersonal Theory and Research from 1999 to 2000.