 Dissociability and localizability. To say that a system is functionally dissociable is to say that it can be selectively impaired, that is, damaged or disabled with little or no effect on the operation of other systems. As the neuropsychological record indicates, selective impairments of this sort have frequently been observed as a consequence of circumscribed brain lesions. Standard examples from the study of vision include prosopagnosia (impaired face recognition), achromatopsia (total color blindness), and akinetopsia (motion blindness); examples from the study of language include agrammatism (loss of complex syntax), jargon aphasia (loss of complex semantics), alexia (loss of object words), and dyslexia (impaired reading and writing). Each of these disorders have been found in otherwise cognitively normal individuals, suggesting that the lost capacities are subserved by functionally dissociable mechanisms.