Classic Stroop Color Words Produce No Stroop Effect When the Display Characteristics Are Based Upon Emotional Stroop Studies With Subliminal Presentations

Two forms of the Stroop task have produced contradictory findings regarding unconscious perceptual processing. Emotional Stroop task studies with prime words presented at an objective threshold (i.e., subliminal) produce Stroop-like effects, but comparable studies conducted with classic Stroop stimuli do not produce Stroop effects. We tested the possibility that differences in the display appearance might explain this discrepancy. Color word prime stimuli from the traditional Stroop task were used with display characteristics based upon the emotional Stroop studies. There was a Stroop effect for the relatively long prime stimulus durations (59, 87, or 108 milliseconds) but not for the brief durations (18, 24, or 38 milliseconds). Accordingly, the discrepancy in research findings cannot be attributed to simple differences in display methodology. The failure to find strong evidence of unconscious perceptual processing is consistent with the negative findings from some emotional Stroop studies that use subliminal stimulus presentations.