In neuropsychology, dysmetria (literally meaning wrong length) is a specific kind of ataxia (loss of control of motor movements) where a patient cannot properly carry out an intended motor movement, and they tend to misjudge the target by overshooting it, undershooting it, or have an improper velocity or rate of the action. Schmahmann (1991) proposed that there also existed a ‘dysmetria of thought.’ He later proposed (2004) the cerebellar cognitive affective syndrome (CCAS), with the following symptoms: (1) problems with executive functions such as poor planning, deficient abstract reasoning, working memory problems, trouble with multitasking and set-shifting, decreased verbal fluency; (2) impaired visuospatial cognition including disorganization and poor visuospatial memory; (3) personality changes such as flattening or blunting of emotions, disinhibition or inappropriate behaviors; (4) language difficulties including troubles with prosody (appropriate variations in the melody, tone, quality and accents used in speaking), word-finding difficulty, and grammatical errors (not necessarily because of a poor environmental upbringing). He also concluded that the syndrome was associated with an overall lowering of intellectual functioning. It is important to note that Schmahmann developed this syndrome based on patients with strokes, tumors, atrophy, or infections of the cerebellum. One interesting area of future research could be a screening for CCAS in populations where cerebellar compromise was not suspected in order to determine whether CCAS can appear without obvious cerebellar damage. In other words, in people not suspected of cerebellar damage, is it still possible to have word fluency problems, deficient abstract reasoning, inappropriate, impulsive, or erratic behaviors, poor grammar, strange word choices, neologisms (coining new words as children often do), or highly superficial wordings because of subtle cerebellar compromise?
Schmahmann, J. D. (2004). Disorders of the cerebellum: Ataxia, dysmetria of thought, and the cerebellar cognitive affective syndrome. Journal of Neuropsychiatry Clinical Neuroscience, 16(3), 367-378.