Four basic models in personality research (trait psychology, psychodynamics, situationism, and interactionsim) are reviewed and compared with respect to (a) types of laws sought, (b) determinants of behavior, (c) units of analysis, (d) the consistency vs specificity issue, (e) ontogenetic development of behavior, and (f) research strategies and populations sampled. An analysis of the controversy between the trait model and the interactional model suggests that the trait model is limited as a basis for use in description and prediction of behavior and as a general basis for personality research. Empirical results support an interactional view of behavior, in which actual behavior is determined by a continuous and multidirectional interaction between person variables and situation variables. The issues and research on situational determinants of behavior are reviewed, and the need for more systematic psychological studies of situations is stressed. Major features of the interactional model of personality are discussed, and the necessity of developing methods for investigating continuous interaction processes is emphasized. (3 p ref) (PsycINFO Database Record (c) 2006 APA, all rights reserved)