“…However, its occurrence in some normal subjects rules out equating dysrhythmia with vestibular system pathology (Hammersma 1957;Clement 1970;Jongkees 1973). Dysrhythmia is typically evaluated subjectively (e.g., Lidvall 1961), though methods for quantifying it have been suggested (Proctor, Carli, and Davis 1972;Henriksson et al 1976). Dysrhythmia is lessened by maintaining mental alertness (Mahoney, Harlan, and Bickford 1957;Lidvall 1961Lidvall , 1962Collins 1965aCollins , 1965b, by minimizing visual suppression (Stahle 1956;Riesco-MacClure and Stroud 1960;Henriksson et al 1972), and by counteracting habituation (Forssman, Henriksson, and Dolowitz 1963;Forssman 1964;Henriksson et al 1972).…”