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.     

Information processing components of substitution test performance

Although substitution tests have been included in tests of intelligence for years, the underlying abilities they measure have still not been clearly determined. This study used componential analysis to investigate the information-processing components underlying substitution test performance. The bases of sex and age differences were also of interest. One hundred subjects from each of three age groups (9–11, 18–25, and 60–89 years) were tested.The componential analysis found that substitution tests measure perceptual speed and, to a lesser extent, memory ability and writing speed. The component “Stimulus Orientation, Response Initiation, and Execution” was related to substitution test performance in the sample of children and the sample of older adults but not in the sample of younger adults. Verbal ability was not significantly related to substitution test performance in the two younger samples but was strongly related to substitution performance in the oldest sample. Although females outperformed males on the Symbol Digit Test, males did as well as females on the computerized tasks. Apparently, sex differences in substitution test performance cannot be explained by the components of the test measured here.     

TEACHING FUNCTIONAL COMMUNITY SKILLS TO AUTISTIC CHILDREN USING NONHANDICAPPED PEER TUTORS

In this study, two autistic children were paired with normal peers who, after pretraining sessions, taught community skills to the autistic children. Data were collected during three conditions: baseline, modeling, and peer tutoring. Results demonstrated that no identified skills were acquired during the baseline and modeling conditions. However, direct instruction of each child by a peer tutor resulted in the learning and maintenance of functional community skills.     

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.     

Delayed commitment in spoken word recognition: Evidence from cross-modal priming

Using the cross-modal priming paradigm, we attempted to determine whether semantic representations for word-final morphemes embedded in multisyllabic words (e.g., /lak/ in /hεmlak/) are independently activated in memory. That is, we attempted to determine whether the auditory prime, /hεmlak/, would facilitate lexical decision times to the visual target,key, even when the recognition point for/hεmlak / occurred prior to the end of the word, which should ensure deactivation of all lexical candidates. In the first experiment, a gating task was used in order to ensure that the multisyllabic words could be identified prior to their offsets. In the second experiment, lexical decision times for visually presented targets following spoken monosyllabic primes (e.g., /lak/-key) were compared with reaction times for the same visual targets following multisyllabic pairs (/hεmlak/-KEY). Significant priming was found for both the monosyllabic and the multisyllabic conditions. The results support a recognition strategy that initiates lexical access at strong syllables (Cutler & Norris, 1988) and operates according to a principle of delayed commitment (Marr, 1982).     

Pooling peripheral information: Averages versus extreme values

Suppose, as an idealization, that sensory intensity is coded in peripheral channels as identical Poisson pulse trains with intensity parameter a power function of signal intensity. Discrimination models based on either an average count computed over a fixed time or an average time computed for a fixed count per channel have difficulty in fitting the Weber function ($\text{ΔI}\text{I}$ versus I) if the free parameters are constrained to ranges determined from other experiments (magnitude estimation, reaction time). Here we study a different decision rule, namely, the most extreme observation in either the counting or timing mode. Our extremum-counting model, but not two timing ones, accounts very nicely for the Weber function. However, the ROC curves for these extremum models, which agree in shape with data of Green and Luce, yield estimates for the intensity parameter which are much larger than predicted by the power function growth used to calculate ΔI and about twice as large as those estimated from reaction time data collected in the same experiment.     

An observable property equivalent to a choice model for discrimination experiments

The choice model considered by Luce in an earlier work is stated in terms of unobservable parameters. In this paper a consequence of the model, involving only observables, is shown to be equivalent to the model.This work was supported in part by National Science Foundation Grants NSF G-8864 and NSF G-17637 to the University of Pennsylvania.     

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.