Toward a cognitive neuropsychology of awareness: implicit knowledge and anosognosia.

Although a systematic cognitive neuropsychology of awareness has not yet emerged, a number of phenomena reported in the literature provide an empirical basis for developing it. The present discussion focusses on two such phenomena: implicit knowledge, which refers to knowledge that is expressed in task performance unintentionally and with little phenomenal awareness; and anosognosia, which refers to unawareness of neuropsychological deficits. Two types of theoretical accounts of these phenomena are discussed. A first order theoretical account entails postulating damage to, or disconnection of, a system or process that generates awareness across multiple domains. A second-order account does not postulate disruption of a cross-domain awareness mechanism, but instead appeals to difficulties in gaining access to particular kinds of domain-specific information that are associated with aware expressions of knowledge in individual domains. Instances of first- and second-order accounts are illustrated with examples from studies of memory and amnesia. The relation between implicit knowledge and anosognosia is also discussed.