Much of the evidence to support the

Much of the evidence to support the critical period theory comes from observations of patientssuffering from aphasia, which is a loss of language abilities associated with brain damage frominjury or disease. A vast amount of evidence has accumulated over the last one hundred yearsthat language is localised in the brain's left hemisphere. Seventy percent of adult patients withsome injury to the left hemisphere suffer some language disability. However, patients withinjuries to the right hemisphere remain able to speak and understand language perfectly. Theirproblems are with such activities as recognising faces and patterns or finding their way from oneplace to another.