Anosognosia /æˌnɒsɒgˈnəʊsɪə/ is a condition in which a person who suffers disability seems unaware of the existence of his or her disability. Unlike denial, which is a psychological defence mechanism, anosognosia is rooted in physiology (for example, damage to the frontal or parietal lobe due to illness and disease). This may include unawareness of quite dramatic impairments, such as blindness or paralysis. It was first named by the neurologist Joseph Babinski in 1914. Relatively little has been discovered about the cause of the condition since its initial identification. The word comes from the Greek words nosos, "disease", and gnosis, "knowledge", with an- or a- as a negative prefix.