Is the Self-Prioritization Effect Driven by the Same Mechanism as the Simon Effect?

The current thesis explores the underlying mechanism of the Self-Prioritization Effect (SPE), which refers to more accurate and faster responses in matching self-shape trials compared to matching other-shape trials in the shape-matching task. [A3.1]The shape-matching task includes two phases. In the learning phase, participants learn to associate a label (e.g., self and stranger) with a specific geometric shape (e.g., square and triangle). In the subsequent test phase, participants need to indicate if the presented shape-label pair matches the learned association. Recent studies suggest that a part of the SPE can be explained as an S-R compatibility phenomenon. The present study aimed to test whether the SPE exhibits the same temporal decay pattern observed in the Simon Effect, a well-known S-R compatibility phenomenon (Cespón et al., 2020; Simon & Small Jr., 1969). According to the decay hypothesis, increasing the temporal distance between stimulus presentation and response onset reduces the Simon effect (Hommel, 1993; Kornblum et al., 1990). Therefore, we applied a variant of the shape-matching task, in which an auditory go-signal was added to prompt participants to respond. The go-signal was presented either simultaneously with the shape–label pair or after a delay (SOA: 0 ms, 1,500 ms, 3,000 ms), and the study explored whether the magnitude of the SPE varied significantly as a function of this interval between stimulus onset and the go-signal in shape–label matching trials. Fifty-three [A4.1]participants initially completed the study. Following data screening, two participants were excluded from the final analyses, resulting in a sample of N = 51 participants. A Generalized Linear Mixed Models analysis revealed a significant interaction between condition and stimulus onset asynchrony (SOA), indicating that the SPE was largest at SOA = 0 ms, substantially reduced at SOA = 1,500 ms, and near zero at SOA = 3,000 ms. This suggests that the SPE shares a decay pattern with S-R compatibility phenomena.