Cognitive interference modulates speech acoustics in a vowel-modified Stroop task

AbstractHow do cognitive processes influence speaking? We used a novel variant of the Stroop test to measure whether cognitive inhibition could modulate acoustic properties of speech. Participants named the color of words in three categories: 1) congruent (e.g. “red” written in red), 2) color-incongruent (e.g. “green” written in red), and 3) vowel-incongruent, with phonetic properties that partially matched the text color (e.g. “rid” written in red). We hypothesized that the cognitive effort of inhibiting reading in this third condition—saying “red”, not “rid”—could affect the acoustics of the spoken response. A classic Stroop effect was evident: congruent trials were faster than color-incongruent trials. Interestingly, vowel-incongruent trials did not show this reaction time difference, but spoken vowels from these trials were systematically biased away from the visually-presented text. Thus, the inhibition of a competing target is manifest in an accentuation of the acoustic contrast between the spoken and inhibited words.

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