Michael S. Vitevitch

When Words Compete: Levels of Processing in Perception of Spoken Words:

Current theories of spoken-word recognition posit two levels of representation and process: lexical and sublexical. By manipulating probabilistic phonotactics and similarity-neighborhood density, we attempted to determine if these two levels of representation have dissociable effects on processing. Whereas probabilistic phonotactics have been associated with facilitatory effects on recognition, increases in similarity-neighborhood density typically result in inhibitory effects on recognition arising from lexical competition. Our results demonstrated that when the lexical level is invoked using real words, competitive effects of neighborhood density are observed. However, when strong lexical effects are removed by the use of nonsense word stimuli, facilitatory effects of phonotactics emerge. These results are consistent with a two-level framework of process and representation embodied in certain current models of spoken-word recognition.

A web-based interface to calculate phonotactic probability for words and nonwords in English.

Phonotactic probability refers to the frequency with which phonological segments and sequences of phonological segments occur in words in a given language. We describe one method of estimating phonotactic probabilities based on words in American English. These estimates of phonotactic probability have been used in a number of previous studies and are now being made available to other researchers via a Web-based interface. Instructions for using the interface, as well as details regarding how the measures were derived, are provided in the present article. The Phonotactic Probability Calculator can be accessed athttp://www.people.ku.edu/~mvitevit/PhonoProbHome.html.

The influence of phonological similarity neighborhoods on speech production.

The influence of phonological similarity neighborhoods on the speed and accuracy of speech production was investigated with speech-error elicitation and picture-naming tasks. The results from 2 speech-error elicitation techniques-the spoonerisms of laboratory induced predisposition technique (B. J. Baars, 1992; B. J. Baars & M. T. Motley, 1974; M. T. Motley & B. J. Baars, 1976) and tongue twisters-showed that more errors were elicited for words with few similar sounding words (i.e., a sparse neighborhood) than for words with many similar sounding words (i.e., a dense neighborhood). The results from 3 picture-naming tasks showed that words with sparse neighborhoods were also named more slowly than words with dense neighborhoods. These findings demonstrate that multiple word forms are activated simultaneously and influence the speed and accuracy of speech production. The implications of these findings for current models of speech production are discussed.

Phonetic priming, neighborhood activation, and PARSYN

Perceptual identification of spoken words in noise is less accurate when the target words are preceded by spoken phonetically related primes (Goldinger, Luce, & Pisoni, 1989). The present investigation replicated and extended this finding. Subjects shadowed target words presented in the clear that were preceded by phonetically related or unrelated primes. In addition, primes were either higher or lower in frequency than the target words. Shadowing latencies were significantly longer for target words preceded by phonetically related primes, but only when the prime-target interstimulus interval was short (50 vs. 500 msec). These results demonstrate that phonetic priming does not depend on target degradation and that it affects processing time. We further demonstrated that PARSYN—a connectionist instantiation of the neighborhood activation model—accurately simulates the observed pattern of priming.

Phonotactics, Neighborhood Activation, and Lexical Access for Spoken Words

Probabilistic phonotactics refers to the relative frequencies of segments and sequences of segments in spoken words. Neighborhood density refers to the number of words that are phonologically similar to a given word. Despite a positive correlation between phonotactic probability and neighborhood density, nonsense words with high probability segments and sequences are responded to more quickly than nonsense words with low probability segments and sequences, whereas real words occurring in dense similarity neighborhoods are responded to more slowly than real words occurring in sparse similarity neighborhoods. This contradiction may be resolved by hypothesizing that effects of probabilistic phonotactics have a sublexical focus and that effects of similarity neighborhood density have a lexical focus. The implications of this hypothesis for models of spoken word recognition are discussed.

The facilitative influence of phonological similarity and neighborhood frequency in speech production in younger and older adults

A tip-of-the-tongue (TOT) elicitation task and a picture-naming task were used to examine the role of neighborhood frequency as well as word frequency and neighborhood density in speech production. As predicted for the younger adults in Experiment 1, more TOT states were elicited for words with low word frequency and with sparse neighborhoods. Contrary to predictions, neighborhood frequency did not significantly influence retrieval of the target word. For the older adults in Experiment 2, however, more TOT states were elicited for words with low neighborhood frequency. Furthermore, in Experiment 3, pictures with high neighborhood frequency were named more quickly and accurately than pictures with low neighborhood frequency. These results show that the number of neighbors and the frequency of those neighbors influence lexical retrieval in speech production. The facilitative nature of these factors is more parsimoniously accounted for by an interactive model rather than by a strictly feedforward model of speech production.

The neighborhood characteristics of malapropisms.

This study examined the phonological neighborhood characteristics (frequency, density, and neighborhood frequency) of 138 malapropisms. Malapropisms are whole word substitutions that are phonologically, but not semantically, related. A statistical analysis of a speech error corpus suggests that neighborhood density and word frequency differentially affected the number of malapropisms. Specifically, a greater number of malapropisms were found among high frequency words with dense neighborhoods than with sparse neighborhoods. Exactly the opposite pattern was found among low frequency words. That is, more errors were found among low frequency words with sparse neighborhoods than with dense neighborhoods. More malapropisms resided in low frequency neighborhoods than in high. The average word frequency, average neighborhood density, and average neighborhood frequency of the malapropisms were significantly lower than the same averages computed from randomly sampled control words. Finally, more target words were replaced by error words that had relatively higher frequency than by error words that had relatively lower frequency. The implications of these findings for models of lexical representation and processing are discussed.

Sublexical and Lexical Representations in Speech Production: Effects of Phonotactic Probability and Onset Density.

Phonotactic probability, neighborhood density, and onset density were manipulated in 4 picture-naming tasks. Experiment 1 showed that pictures of words with high phonotactic probability were named more quickly than pictures of words with low phonotactic probability. This effect was consistent over multiple presentations of the pictures (Experiment 2). Manipulations of phonotactic probability and neighborhood density showed only an influence of phonotactic probability (Experiment 3). In Experiment 4, pictures of words with sparse onsets were named more quickly than pictures of words with dense onsets. The results of these experiments provide additional constraints on the architecture and processes involved in models of speech production, as well as constraints on the connections between the recognition and production systems.

Change deafness: The inability to detect changes between two voices.

A shadowing task was used to demonstrate an auditory analogue of change blindness (the failure to detect a change in a visual scene), namely change deafness. Participants repeated words varying in lexical difficulty. Halfway through the word list, either the same or a different talker presented the words to participants. At least 40% of the participants failed to detect the change in talker. More interesting is that differences in shadowing times were found as a function of change detection. Alternative possibilities to the change detection phenomenon were ruled out. The results of these experiments suggest that the allocation of attention may influence the detection of changes as well as the processing of spoken words in complex ways.

The curious case of competition in Spanish speech production

In previous studies in English examining the influence of phonological neighbourhood density in spoken word production, words with many similar sounding words, or a dense neighbourhood, were produced more quickly and accurately than words with few similar sounding words, or a sparse neighbourhood. The influence of phonological neighbourhood density on the process of spoken word production in Spanish was examined with a picture-naming task. The results showed that pictures with Spanish names from sparse neighbourhoods were named more quickly than pictures with Spanish names from dense neighbourhoods. The present pattern of results is the opposite of what has been previously found in speech production in English. We hypothesise that differences in the morphology of Spanish and English and/or the location in the word where phonological neighbours tend to occur may contribute to the processing differences observed in the two languages.