Self-related information consistently receives privileged processing, a phenomenon known as the self-prioritization effect (SPE). In contrast, the joint memory effect (JME) refers to enhanced memory for information associated with a task partner. This study investigated temporal and functional dynamics of these effects during encoding and retrieval using event-related potentials (ERPs). In Experiment 1, participants performed an incidental encoding task followed by intentional retrieval. In Experiment 2, the same encoding task was followed by incidental retrieval. In the encoding task, participants judged whether each word belonged to the self-category. In the intentional retrieval task, they made old/new judgments for previously presented words, whereas in the incidental retrieval task, they counted target words. During encoding, self-related words elicited reduced N400 amplitudes, increased P3b amplitudes, and shorter P3b latencies, indicating greater expectancy, stronger attentional allocation, and faster evaluation. During retrieval, late positive components (LPCs) revealed robust SPEs under both intentional and incidental conditions, whereas the JME emerged only during intentional retrieval. These findings show that self-relevance exerts a pervasive influence on memory, independent of retrieval goals, whereas partner-related information depends more on task context. The results clarify how social labels modulate encoding and retrieval, highlighting the robustness of self-related prioritization and the conditional nature of joint memory.
Kato et al. (Sun,) studied this question.