Abstract: Self-relevant information is crucial for human survival and development. Previous studies have shown that the congruence between the implicit meanings of stimuli and the self-concept can facilitate the processing of self-related information, suggesting that self-cognition may be shaped and activated through implicit associations within dynamic environmental contexts. In the Chinese cultural context, completeness is often associated with integrity, unity, and perfection, serving as a meaningful implicit backdrop for examining how concrete perceptual features are linked to abstract self-cognition. However, it remains unclear whether complete shapes, as concrete perceptual cues, can further enhance the processing advantage for self-related information through implicit associations. Therefore, the present study investigated whether shape completeness modulates self-prioritization in perceptual decision-making. We hypothesized that associations between self-referential labels and complete shapes would receive preferential processing, resulting in a self-complete association advantage.
The present study comprised two experiments. Experiment 1 employed a 2 (Shape Completeness: complete, incomplete) × 2 (Encoding: self-related, stranger-related) × 2 (Match Type: match, mismatch) within-subjects design, combining hierarchical drift diffusion modeling and event-related potential techniques to investigate the impact of shape completeness on self-related processing and its underlying cognitive and neural mechanisms. Participants completed a perceptual matching task involving two phases. During the associative phase, they learned associations between two geometric shapes (i.e., complete and incomplete shapes) and two identity labels (i.e., self and stranger). In the subsequent shape-label matching phase, participants judged whether each presented shape-label pair matched the previously learned associations. Thirty-five college students participated in Experiment 1, and valid data from 30 participants (22 females, 8 males) were retained for analysis. EEG data were recorded from 64 scalp sites according to the standard international 10-20 system. The ERP components N1, P2, N2, early LPP, and late LPP were analyzed as indices of different temporal stages underlying the influence of shape completeness on self-related processing. Experiment 2 utilized a 2 (Group: self-complete/stranger-incomplete rule, self-incomplete/stranger-complete rule) × 2 (Encoding: self, stranger) × 2 (Match Type: match, mismatch) mixed design. Sixty college students (18 males, 42 females) were recruited and randomly assigned to two groups of 30 each. In this non-reversal design, each participant was assigned only one fixed identity-shape association, thereby excluding potential confounding effects from rule switching.
The behavioral results of Experiment 1 revealed a stable self-prioritization effect: compared with stranger-related associations, self-related associations yielded shorter response times, higher accuracy, greater perceptual sensitivity, and lower response criteria. In addition, a completeness advantage was observed, such that complete-shape associations were processed more efficiently than incomplete-shape associations. More importantly, on match trials, self-complete associations exhibited shorter response times, higher accuracy, and lower response criteria than both stranger-complete and self-incomplete associations, indicating a specific processing advantage for self-complete associations. The hierarchical drift diffusion modeling results further indicated that this self-complete association advantage was supported by a faster evidence accumulation rate and shorter non-decision times. The ERP results showed that, compared with self-incomplete and stranger-complete associations, self-complete associations elicited reduced N1 amplitudes in the 80-130 ms time window, attenuated N2 amplitudes at 250-350 ms, and larger early LPP amplitudes at 450-650 ms. Given that the N1 effect may be jointly modulated by block-level mapping rules and condition-related factors, the N1 finding was interpreted cautiously as an early processing difference specific to self-complete associations. Experiment 2 demonstrated that the self-complete association advantage persisted without rule reversal, indicating that this effect was not attributable to switching costs arising from rule changes.
Taken together, these results demonstrate that self-prioritization is not only reflected in the baseline preferential processing of self-related stimuli but is also modulated by the congruence between perceptual features and the self-concept. Complete-shape cues enhanced the processing priority for self-related associations, indicating that complete shapes may facilitate self-related processing by increasing the compatibility between perceptual completeness and the self-concept. This conclusion is corroborated by behavioral, diffusion-modeling, and ERP evidence, revealing that the self-complete association advantage involves faster evidence accumulation, shorter non-decision times, early processing differences, and enhanced late-stage attentional integration.

Key words: completeness cue, self-prioritization effect, drift diffusion model, ERPs