In repeated-event paradigms, participants typically recall more accurate details from the first and final instances of a series of similar events (i.e., long-term primacy and recency effects). Encoding-level differences are assumed to contribute to these patterns; participants may encode distinct attributes of details of the boundary instances that subsequently facilitate source monitoring, although to date, there is no direct evidence of encoding-level mechanisms because repeated-event memory is typically assessed using free-recall paradigms that contaminate performance with retrieval-level processes. We focused on encoding-level mechanisms more directly by measuring reaction times in recognition tasks that either did or did not require source monitoring. We expected to observe faster hits in the task that did not require source attribution, and we also expected faster hits for the boundary instances. Participants viewed four videos, and after a 10–15-minute delay completed a recognition task. In Experiment 1 (N = 168, between-subjects), participants decided whether an item was old (i.e., presented in any video) or new, or whether an item was presented in video 1/2/3/4 or was new. In Experiment 2 (N = 160, within-subjects), the old/new decision was followed by an instance attribution decision. We found faster hits in the old/new task compared to the instance-attribution task. In the instance-attribution task, items from the boundary instances were accurately attributed faster compared to items from the middle instances. We found further support for the primacy and recency effects in measures of confidence, memory judgments, recognition accuracy and discriminability, and confidence-accuracy calibration.