Perceptual conflict-induced late positive complex in a modified Stroop task

Abstract

To investigate the functional significance of the late positive complex (LPC) in the Stroop task, the present study recruited 22 participants and had them report the color of words in the classical Stroop task and the rotation state of words in a Rotation judgment task. Color words whose ink color was either congruent (CON) or incongruent (INCON) with the word's meaning were presented in both tasks. Consistent with previous studies, the N450 and LPC were observed in the Stroop task, accompanied by slowed reaction time (RT) in the INCON condition compared with the CON condition. Notably, a larger LPC was observed in the INCON condition than in the CON condition in the Rotation task, while RT and accuracy were comparable between the two conditions. Because the incongruence between ink color and word meaning was independent from the response, and neither influenced accuracy nor RT in the Rotation task, the results suggested that the LPC may have resulted from the perceptual conflict between ink color and word meaning.