EXPRESS: Effects of perceptual redundancy, conceptual redundancy and self-relatedness on categorical responses.

A redundancy gain occurs when perceptually identical stimuli are presented together, resulting in quicker categorization of these paired stimuli compared to lone stimuli. Similar effects have been reported for paired stimuli within the same conceptual category, particularly if the category is self-related. We recruited 528 individuals across three related studies to investigate whether, during perceptual and conceptual redundancy, such self-bias effects on foreground stimuli are modulated by natural versus urban backgrounds. Here, we highlight our observations pertaining to perceptual and conceptual redundancy effects of the foreground stimuli. In our first experiment, response options were randomized per trial. Results showed reaction time gains for perceptually identical stimuli, but this advantage was not modulated by self/other categorization. However, slower reaction times were observed for conceptually-related stimulus pairs, and were influenced by self/other categorization. The second experiment replicated the methods of earlier studies of redundancy and observed comparable results to Experiment 1: A perceptual redundancy gain unmodulated by self/other categorization, yet, for conceptual redundancy, no gain/cost but effects of self/other categorization. In the third experiment, self/other categories were substituted with arbitrary A/B categories: Once more, there was a perceptual redundancy gain and no conceptual redundancy gain. Notably, A/B categorisation produced effects equivalent to self/other categorisation. Overall, these findings challenge previous research on the facilitated early processing of conceptually-related stimuli and suggest that self-relatedness may not exert a unique effect on stimulus processing beyond attentional and response preferences during categorization. Our study motivates further research to understand conceptual categorization and redundancy gain effects.