Use of phonological and lexical cues in the resolution of perceptual-lexical ambiguities by listeners differing in working memory span

The purpose of this research is to examine why there are differences in language processing between listeners with high and low working memory spans (WMS). Possible reasons include: differences in auditory perception of the speech signal, differences in coding the signal at the phonological, lexical and/or sentence levels, interaction between processing at different levels, differences in rehearsal capacity for speech, and/or, differences in generating and/or evaluating alternative interpretations to ambiguous signals. With regard to the matter of how processing at different levels might interact, the following questions are examined: Which aspects of spoken language processing interact with each other? To what extent do they interact with each other? and, Does the pattern of interaction differ for groups that vary in working memory limitations? This research makes new contributions in two ways: 1) the relationship between working memory span and the domain of listening is examined, (rather than reading, on which most of the research has been focussed to date), and 2) the linguistic signal presented is made ambiguous through perceptual degradation in order to examine the relationship between perception, working memory and language comprehension. In the first three experiments, target words which varied in terms of a minimal pair contrast were embedded in a variety of sentences and presented in varying degrees of background noise to high and low WMS adult listeners. As the background noise (and consequently the acoustical confusions of speech sounds) increased, the target words were rendered increasingly ambiguous. The listeners were asked, in each experiment, to identify the target word. The sentences varied in the degree to which they contained contextual information at the lexical level in Experiment 1, and at the sentence level in Experiments 2 and 3. The manner in which high and low WMS listeners used phonological, lexical and sentence level information processing components was compared. The fourth experiment employed a gating task (following Grosjean, 1980), in which the initial portion of the word increased in duration on each trial until the word was correctly identified by the listener. Thus it was possible to directly assess whether listeners generate multiple alternatives to ambiguous words (Carpenter et al., 1995) or evaluate alternatives differently (e.g., through inhibitory mechanisms; Stoltzus, Hasher, & Zacks, 1996). In Experiments 2-4, temporal auditory processing (via gap-detection scores) was also compared to comprehension performance in order to evaluate whether it could help to explain group differences in processing ambiguous spoken language. The results of the first and fourth experiments provide evidence that high WMS listeners discriminate phonological cues better, generate more alternatives to ambiguous words, are better at inhibiting incorrect responses, and, overall, process phonological cues relatively independently of lexical knowledge. The second, third and fourth experiments showed that sentence level knowledge interacts with processing of phonological cues similarly for both WMS groups and that high WMS listeners demonstrate superior rehearsal capacity for phonological information. Temporal auditory processing as measured by gap detection does not appear to be related to spoken language processing for either group. Therefore, the results show that the differences in language processing between high and low WMS groups appear to lie in the interaction between lexical and phonological processing, and generation and evaluation of alternatives, but fail to provide evidence that there are differences in sentence processing or temporal auditory processing. The results of this research contribute to relatively unexplored aspects of existing WMS models.Arts, Faculty ofPsychology, Department ofGraduat