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The Achromatic ‘Philosophical Zombie’, a Syndrome of Cerebral Achromatopsia with Color Anopsognosia

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A, Carota
A, Carota
Pasquale Calabrese at University of Basel
Pasquale Calabrese
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We describe a patient with persistent cerebral achromatopsia occurring after bilateral occipital strokes. Blinded color recognition was assessed with a computerized experimental paradigm and the patient reported the degree of confidence in the response exactness on a visual percent scale. Color recognition was accurate and above chance (Fisher's exact test, p < 0.002). The degree of confidence in the answers showed a significant correlation with recognition scores (Spearman rank order correlation, p < 0.0001). These findings constitute the exceptional condition of what we called color anopsognosia (not knowing of seeing colors) and recall the theoretic figure of the 'philosophical zombie'. However, the cognitive mechanisms of the dissociation between a subjective colorless vision and good performance for color naming still remain poorly understood.
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The Achromatic ‘Philosophical Zombie’, a Syndrome of Cerebral Achromatopsia with Color Anopsognos
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... Indeed, there is evidence that at least some blindsight patients do report some visual experience when carefully queried Ffytche and Zeki, 2011). Similar to blindsight type 2, there is a case of an achromatic patient, who reports color blindness after occipital brain damage but performs well in color discrimination tasks, and his confidence in being correct in the task strongly correlates with task performance (Carota and Calabrese, 2013). Again, it is controversial whether the performance of achromatic patients occurs in complete absence of color experiences or is mediated by residual conscious contents of color (Heywood et al., 1998). ...
... Nevertheless, it seems rather odd why participants would readily acknowledge feelings of rightness while being reluctant to admit visual contents. Moreover, the present pattern of confidence without visibility seems to be reasonably robust as it was replicated in patients (Sahraie et al., 1998;Carota and Calabrese, 2013) and healthy human observers in a range of tasks (Schlagbauer et al., 2012;Charles et al., 2013;Zehetleitner and Rausch, 2013). Finally, the analysis of metacognitive sensitivity suggests that the effect of confidence and visibility as contents of subjective reports is not exhausted by criterion setting. ...
... However, although participants had conscious access when they reported they felt confident about task response, they reported no conscious visual experience. A similar pattern was reported from a patient suffering from achromatopsia (Carota and Calabrese, 2013): After bilateral temporal-occipital lesions, that patient reports to be color-blind although he performs accurately in a color recognition task. A potential explanation why the relation between phenomenal consciousness and conscious access varies is the number of items in the display: Visual short-term memory always used arrays of multiple stimuli. ...
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  • Apr 2016
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Thesis
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Article
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Article
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Article
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