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Comparing verbal and nonverbal Stroop tasks: A synesthesia case study

posted Apr 6, 2012, 2:02 AM by Chris Koch
Kelsi Buswell & Christopher Koch

Summary.  Synesthesia is a condition in which senses are crossed so that one sensory modality evokes a response from another.  A common form of this condition is grapheme-color synesthesia.  In this type of synesthesia, numbers or letters are associated particular colors.  The Stroop task requires that an individual identify the color a word is printed in.  When the word (e.g., RED) matches the color (red), responses are relatively fast and can show Stroop facilitation.  However, when the word (RED) does not match the color (e.g., blue), responses are relatively slow indicating Stroop interference.  Modified versions of the Stroop task have been used with synesthetes (Elias, Saucier, Hardie, & Sarty, 2003).  Results from these studies suggest that graphemes automatically elicit a color experience.  Furthermore, the results are consistent with associations at the semantic and perceptual levels (Mroczko, Metsinger, Singer, & Nikolić, 2009).  These levels may also represent different underlying mechanisms for processing interference-inducing stimuli (cf., Berteletti, Hubbard, & Zorzi, 2010; Mroczko, Metsinger, Singer, & Nikolić, 2009).  In the present study, verbal and nonverbal Stroop tasks are compared to gain a more thorough understanding of the manner in which different Stroop tasks are processed.  D.P. completed a synesthesia interview (Grossenbacher & Lovelace, 2001) and a standardized test battery for synesthesia (Eagleman, Kagan, Nelson, Sagaram, & Sarma, 2007).  These assessments indicated that D.P. is a grapheme-color synesthete (associator type).  D.P. was administered three Stroop tasks including the Color and Word Stroop Test (Golden, 1978), a nonverbal Stroop task from the Leiter-3, and the Nonverbal Stroop Card Sorting Task (Koch & Roid, 2012).  The results show that D.P. performs the verbal and nonverbal Stroop tasks within normal limits.  However, the process by which the Nonverbal Stroop Card Sorting Task is completed may be quite different.  Instead of sorting cards by color, the cards are sorted by “odd” and “even”.  Additional follow-up research is being conducted to determine how D.P. processes each individual card in the card sorting task.  Implications for understanding Stroop processing, especially nonverbal Stroop processing, are discussed.

Poster presented at the 2012 Meeting of the Society for Neuroscience Oregon Chapter

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Chris Koch,
Apr 6, 2012, 2:02 AM
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