• parkinsonism;
  • bradyphrenia;
  • delayed auditory feedback;
  • reaction time;
  • mental test score;
  • ageing

Sufferers from parkinsonism have difficulty shifting or developing an appropriate mental set. Delayed auditory feedback may, therefore, disrupt their speech more than that of healthy controls. This was the case when 104 subjects with idiopathic parkinsonism and 144 without were compared. Moreover, the disruptive effect was complementary, in discriminating between those with and without clinical parkinsonism, to the response in reaction time to a warning. Unlike the latter, the disruption caused by delayed auditory feedback appeared independent of mental test score results and uninfluenced by consumption of tobacco or anti-parkinsonian therapy. Neither were influenced by a rating of affect. More precise delineation of the mental disorders of parkinsonism is needed in clinical practice, set against background information on prognosis and drug responsiveness.