The Effects of Delayed Auditory Feedback (DAF) on Normal Speakers and the Aphasics

Abstract

There has been little investigation upon the experiment of delayed auditory feedback concerning speech of aphasic patients. This study was conducted with the aim of evaluating DAF as a possible tool for examining physiological aspects of aphasic speech and language.Normal speakers were 20 men in their fifties and the aphasics were 45 patients of 4 types—amnesic, conduction, sensory and motor — aged from 24 to 74 years. Each subject was asked to read a Japanese 50 syllable table under NAF (normal auditory feedback) and DAF condition with a delay time of 0.2 seconds and feedback level of 90 dB SPL to both ears.The responses of the aphasic patients to DAF were divided broadly into three groups;1) The response of the mild group (amnesic aphasia) was similar to that of a normal speaker — increased vocal intensity, reduced rate of utterance and syllable repetition.2) The response of the severe group (typical sensory or motor aphasia) was characterized by unaffected vocal intensity and articulatory errors in both NAF and DAF.3) The response of the moderate group (conduction aphasia) was in between the mild and the severe groups.