The perceptual loop theory of speech monitoring (Levelt, 1983) claims that inner and overt speech are monitored by the comprehension system, which detects errors by comparing the comprehension of formulated utterances to originally intended utterances. To test the perceptual loop monitor, speakers named pictures and sometimes attempted to halt speech in response to auditory (Experiments 1 and 3) or visual (Experiments 2, 4, and 5) words that differed from the picture name. These stop-signal words were varied in terms of their semantic or phonological similarity to the intended word. The ability to halt word production was sensitive to phonological similarity and, in Experiment 5, to emotional valence, but not to semantic similarity. These results suggest that the perceptual loop detects errors by making comparisons at a level where phonological knowledge is represented. These data also imply that dialogue, back channeling, and other areas where speech production is affected by simultaneous comprehension may operate based on phonological comparisons.
Halting in Single Word Production: A Test of the Perceptual Loop Theory of Speech MonitoringOne of the more striking features of language production is its efficiency and accuracy. Levelt (1989) estimates that we produce about 150 words per minute, but make only one lexical error per 1,000 words. This is especially impressive considering the complexities of word production. When speakers produce words, they start with an idea they wish to communicate, then must retrieve both lexical and phonological information, and finally program a set of motor movements that can then be comprehended by listeners. Despite these complexities, speech production seems relatively effortless and error-free.One reason that errors are relatively infrequent may be that speakers comprehend their own speech to inspect it for errors, thereby allowing them to inhibit and repair erroneous utterances and speak relatively fluently. It is not unusual for speakers to stop and correct themselves when they make an error, sometimes even before the error is externally apparent. This idea has been formalized as the speech monitor.A number of findings in the speech-error record have been used as evidence for an inner speech monitor, such as the fact that phonological speech errors are more likely to result in real words than nonwords (the lexical bias effect). Baars, Motley and MacKay (1975) provided experimental evidence of this effect by using a procedure to elicit Spoonerisms (exchanges of Please address correspondence to: L. Robert Slevc, Department of Psychology 0109, University of California, San Diego, La Jolla, CA 92093-0109, slevc@psy.ucsd.edu Publisher's Disclaimer: This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final citable form. Please note that d...