During the 1960s, information processing became the dominant model in psychology for understanding mental processes. This provided an important theoretical basis for cognitive neuropsychology, as it allowed an explanation of what areas of the brain might be doing (i.e. processing information in specific and specialised ways) and also allowed brain injury to be understood in abstract terms as impairment in the information processing abilities of larger cognitive system.
Methods
The 'lesion method' (using brain injury or lesions to infer cognitive function) was probably best described unwittingly by singer-songwriter Joni Mitchell when she wrote "You don't know what you've got 'till it's gone". By understanding what a person can no longer do, and correlating this with a knowledge of exactly which parts of the nervous system are damaged, it is possible to infer previously undiscovered functional relationships.
By using this method, it should also be possible to discover whether a skill is handled by a single cognitive process or a combination of several working together. For example, if a theory states that reading and writing are simply different skills stemming from a single cognitive process, it should not be possible to find a person who, after brain injury, can write but not read or read but not write. This selective breakdown in skills suggests that different parts of the brain are specialised for the different processes and so the cognitive systems are separable.
The philosopher Jerry Fodor has been particularly influential in cognitive neuropsychology, particularly with the idea that the mind, or at least certain parts of it, may be organised into independent modules. Evidence that cognitive skills may be damaged independently seem to support this theory to some degree, although it is clear that some aspects of mind (such as belief for example) are unlikely to be modular. Ironically, Fodor (a strict functionalist) rejects the idea that the neurological properties of the brain have any bearing on its cognitive properties and doubts the whole discipline of cognitive neuropsychology.
Cognitive neuropsychology also uses many of the same techniques and technologies from the wider science of neuropsychology and fields such as cognitive neuroscience. These may include brain imaging, electrophysiology and neuropsychological tests to measure either brain function or psychological performance.
The principles of cognitive neuropsychology have recently been applied to mental illness, with a view to understanding, for example, what the study of delusions may tell us about the function of normal belief. This relatively young field is known as cognitive neuropsychiatry.
