Vocal Suppression: The Effects of Processing Time and the Nature of the Subsidiary Task

Abstract

<p>There is considerable evidence indicating that speech information plays a part in visual information processing. To translate visual input into a speech code would require some sort of speech recoding stage. One technique widely used to verify the existence of this speech recodinq stage has been the vocal suppression paradigm, where the translation stage is presumed to be interfered with by concurrent irrelevant vocal activity. However, attempts have been made to explain the vocal suppression effect in terms of general cognitive capacity overload, without recourse to speech-specific interference. This thesis represents an attempt to implicate the existence of speech recoding by demonstrating that vocal suppression is, in fact, attributable to interference with subvocal activity.</p> <p>Three experiments are reported. The first indicates that subjects, given control over the rate at which sentences are presented to them, do not choose to read more slowly in an attempt to overcome the vocal suppression effect. The second experiment indicates that even when forced to read at a slower rate, subjects cannot overcome the effect. The final experiment indicates that the suppression effect can occur with a non-verbal interference task. The results are discussed in terms of the distinction between general and speech-specific interference.</p>