Investigation of the influence of visual stimuli on the breakdown of the echo threshold

Abstract

Audiovisual interaction is already known from the ventriloquism effect [W. R. Thurlow and Ch. E. Jack, Percept. Mot. Skills 36, 1171–1174 (1973)]. Synchronously presented auditory and visual stimuli are perceptually grouped and localized as one object. The performed experiments aimed to explore a possible influence of visual stimuli on echo suppression. They focused on investigating whether visual stimuli can also cause a breakdown of the echo threshold. One hypothesis is that the breakdown of echo suppression is caused by violations of the listeners’ expectations concerning the presented scenario. The question is whether this implausibility can be attributed to acoustical reasons. Two different kinds of visual implausibilities were tested by measuring echo threshold with an adaptive paradigm. In the build-up phase of both experiments, visual and auditory parts of the stimuli have been presented from the same direction. In the test phase, the visual stimulus’ direction was altered. The main result of the investigations was that both experiments did not provide any evidence of a visually induced breakdown of the echo threshold. This holds true, even if the position of the auditory event corresponding to the direct sound was changed due to the ventriloquism effect by changing the corresponding visual stimulus’ direction of incidence.