A theory of information integration is applied to attitudes and social judgments, based on a principle of information integration. For quantitative analysis, a simple but general algebraic model of judgment is used, in which each informational stimulus is characterized by two parameters, scale value and weight. Functional measurement procedures are employed to derive equal-interval scales of parameter values. Exact tests based on analysis of variance are given for four applications of the model, and these applications are reconsidered under the further restriction imposed by the averaging hypothesis. Qualitative comparisons are made to several other theories of attitude change. Tendencies toward balance and congruity are shown to be consequences of the principle of information integration. Critical tests between integration theory, and balance and congruity theories are also suggested. Similar comparisons are made to summation theory, logical-consistency theory, assimilation-contrast theory, and similarity-attraction theory. Molar and molecular analyses of communication structure are considered briefly and the analysis of inconsistency resolution within integration theory is also discussed. Finally, it is noted that integration theory has had reasonable success in the areas of learning, perception, judgment, decision making, and personality impressions, as well as attitude change. It may thus provide a beginning to a unified general theory.Attitude change stands out from most continually impinge on the person, in life areas of experimental psychology in the or in the laboratory, and he must integrate nature of its stimuli. In even the simplest them with one another as well as with his investigations of attitudes and opinions, prior opinions and attitudes. Social judgthe stimuli typically carry information at a ments are typically based on a cumulation cognitive level not often reached in other of various pieces of information, sometimes areas of research. Informational stimuli of the most diverse nature. Factual and !This work was supported by grants from the hearsay evidence, rumors, prestige associ-National Science Foundation (GB-6666) and the ations, gesture and appearance, may all a^lS'the SSal tt>» Menfaf bear on the final attitude. Information in-Health to the Center for Human Information Pro-tegration is thus fundamental in attitude cessing,