Michael J. Beran, Ph.D.
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September 1, 2021



Beran, M. J., Washburn, D. A., & Rumbaugh, D. M. (2007).  The Stroop Effect in color-naming of color-word lexigrams by a chimpanzee.  Journal of General Psychology, 134, 217-228. 

The Stroop effect reflects the difficulty in ignoring irrelevant, but automatically processed, semantic information inherent in certain stimuli. With humans, this effect is found when participants are asked to name the color of the letters that make up a word that is incongruent with that color. We tested a chimpanzee that had learned to associate geometric symbols called lexigrams with specific colors. When this chimpanzee was presented with a computer task in which she had to make different responses depending on the color of stimuli presented to her, she showed a Stroop-like effect when her previously-learned symbols for colors were presented in incongruent font colors. Her accuracy performance was significantly poorer with these stimuli than with congruent color-referent lexigrams, non-color-referent lexigrams, and non-lexigram stimuli, although there were not significant differences in response latency. This is a demonstration of color-word interference in a Stroop task with a nonhuman animal.

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