This study investigates the relationship between aspects of parent psychopathology and child egocentrism as measured by the Piagetian Three Mountains Task. Two hypotheses were tested: (1) The overall impairment of the previously hospitalized parent will relate to child egocentric errors on a Piagetian Three Mountains Task; (2) Overall impairment of this parent will be a better predictor of child egocentrism than diagnosis of the parent at the time of the study. Subjects were 112 families, each with a previously hospitalized parent for a psychiatric disorder and a child of age 4, 7, or 10. Measurement of the parent's overall impairment was obtained by the Spitzer-Gibbon-Endicott Global Assessment Scale based on symptomology and levels of social and employment functioning. Diagnosis at the time of the study was made using the DSM-III criteria. Findings supported both hypotheses, suggesting that the usual, ongoing impairment of the "patient" parent is more important than the current diagnosed disorder in producing the developmental difficulties shown by these children in relinquishing egocentric thought patterns. (Author/SS)