Living Reference Work Entry

Encyclopedia of Clinical Neuropsychology

pp 1-2

Date: Latest Version


  • John E. MendozaAffiliated withDepartment of Psychiatry and Neuroscience, Tulane Medical School and SE Louisiana Veterans Healthcare System Email author 


Inability to determine by touch alone certain physical properties of an object such as its texture, density (weight), or resistance to pressure, with difficulties in perceiving size or shape is referred to as amorphognosia. While perhaps seeming a bit artificial, according to Bauer and Demery (2003), the distinction between ahylognosia and amorphognosia apparently traces back to 1935 when a French neurologist, Delay, divided astereognosis into two subtypes of deficits: amorphognosia, which was defined as a difficulty in recognizing the size or shape of an object by touch, and ahylognosia, which was described as a failure to differentiate the “molecular qualities” of an object, such as its density, weight, thermal conductivity, or roughness. Delay also defined a third type of astereognosis, tactile asymboly, which was characterized as the inability to identify an object by touch in the absence of amorphognosia and ahylognosia. These same distinctions were followed by Critchley ...

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