The involvement of reading processes and synesthetic color experiences during the classical and synesthesia Stroop task.

Both synesthetes and non-synesthetes commonly report orthography-based letter-color associations (e.g., B is blue). This study examined whether reading processes can confound results on the synesthesia Stroop by comparing 18 synesthetes and 18 non-synesthetes using full color words and their initial letters. Critically, only stimuli showing non-orthographic synesthetic colors were selected for each synesthete (e.g., R synesthetically perceived as yellow) and congruency was based on orthography (e.g., R in red) and not on synesthetes' consistently reported color experiences. Both groups showed congruency effects in the color-naming task for full color words and their initial letters. Notably, synesthetes showed reduced interference for full color words compared to initial letters over time. Possible accounts for this pattern are discussed. These findings highlight the need to control for orthographic confounds in synesthesia Stroop paradigms by avoiding using initial letters of color words as stimuli, as such associations can mimic true synesthetic effects and lead to false positives. The study deepens our understanding of how reading processes interact with synesthetic experiences during the Stroop task and its synesthesia variation.