2 EXPERIMENTS PRESENTED SS WITH SEQUENCES OF DATA THAT 1ST FAVORED 1 HYPOTHESIS, AND THEN CHANGED TO FAVOR A 2ND HYPOTHESIS. AFTER EACH DATUM SS BECAME MORE OR LESS SURE OF WHICH HYPOTHESIS WAS CORRECT. THEY REFLECTED THIS CHANGE OF OPINION WITH PROBABILITY ESTIMATES, WHICH WERE COMPARED WITH PROBABILITIES CALCULATED BY MEANS OF BAYES' THEOREM. ESTIMATED PROBABILITIES CHANGED FROM FAVORING THE 1ST HYPOTHESIS TO FAVORING THE 2ND LATER THAN DID CORRESPONDING BAYESIAN PROBABILITIES. DATA THAT OCCURRED EARLY IN A SEQUENCE INFLUENCED SS MORE THAN DID LATER DATA-A PRIMACY EFFECT. THIS RESULT AGREES WITH RESULTS OF COMPARABLE EXPERIMENTS ON IMPRESSION FORMATION. (PsycINFO Database Record (c) 2006 APA, all rights reserved)