Four experiments investigated college students' judgments of inter-event contingency. Subjects were asked to judge the effect of a discrete response (tapping a wire) on the occurrence of a brief outcome (a radio's buzzing). Pairings of the possible event-state combinations were presented in a summary table, an unbroken time line, or a broken time line format. Subjects judged the extent to which the response caused the outcome or prevented it from occurring. Across all methods of information presentation, judgments were a positive function of response-outcome contingency and outcome probability. In the unbroken time line condition, judgments of negative response-outcome contingencies were less extreme than judgments of equivalent positive contingencies. Judgments of positive and negative relationships were generally symmetrical in the summary table condition. Summary table judgments were less influenced by the overall probability of outcome occurrence. These judgment differences among format conditions suggest that, depending on the method of information presentation, subjects differently partition event sequences into discrete event pairings. (Author/MNS)