Effects of Degree of Visual Association and Angle of Displacement on the “Ventriloquism” Effect 1

Abstract

The “ventriloquism”, effect refers to the perception of speech sounds as coming from the same direction as the visually observed speaker (even though they are not actually coming from the same direction). Our experiments provide further proof that a necessary condition for this effect is that there be an association between certain critical visual stimuli of the source and the speech sounds. Synchronized movement of the speaker's mouth, associated in the past with speech sounds, is the most important variable. Delay of even .2 sec. between mouth movements of a human speaker, and speech sounds, leads to a large decrease in the “ventriloquism” effect. Results obtained by systematically varying the horizontal angle between the (concealed) sound source and the “visual” source confirm findings of others that strong “ventriloquism” effects can be obtained for an angle as large as 30°. “Ventriloquism” effects can also be obtained for concealed sources placed behind S, though the effect decreases rapidly as the horizontal angle of source placement is changed from a position directly in back of S.