Testing the limits of long-distance learning: learning beyond a three-segment window

Traditional flat-structured bigram and trigram models of phonotactics are useful because they capture a large number of facts about phonological processes. Additionally, these models predict that local interactions should be easier to learn than long-distance ones because long-distance dependencies are difficult to capture with these models. Long-distance phonotactic patterns have been observed by linguists in many languages, who have proposed different kinds of models, including feature-based bigram and trigram models, as well as precedence models. Contrary to flat-structured bigram and trigram models, these alternatives capture unbounded dependencies because at an abstract level of representation, the relevant elements are locally dependent, even if they are not adjacent at the observable level. Using an artificial grammar learning paradigm, we provide additional support for these alternative models of phonotactics. Participants in two experiments were exposed to a long-distance consonant-harmony pattern in which the first consonant of a five-syllable word was [s] or [∫] ("sh") and triggered a suffix that was either [-su] or [-∫u] depending on the sibilant quality of this first consonant. Participants learned this pattern, despite the large distance between the trigger and the target, suggesting that when participants learn long-distance phonological patterns, that pattern is learned without specific reference to distance.     

Accuracy of perceptual and acoustic methods for the detection of inspiratory loci in spontaneous speech

The present study investigates the accuracy of perceptually and acoustically determined inspiratory loci in spontaneous speech for the purpose of identifying breath groups. Sixteen participants were asked to talk about simple topics in daily life at a comfortable speaking rate and loudness while connected to a pneumotach and audio microphone. The locations of inspiratory loci were determined on the basis of the aerodynamic signal, which served as a reference for loci identified perceptually and acoustically. Signal detection theory was used to evaluate the accuracy of the methods. The results showed that the greatest accuracy in pause detection was achieved (1) perceptually, on the basis of agreement between at least two of three judges, and (2) acoustically, using a pause duration threshold of 300 ms. In general, the perceptually based method was more accurate than was the acoustically based method. Inconsistencies among perceptually determined, acoustically determined, and aerodynamically determined inspiratory loci for spontaneous speech should be weighed in selecting a method of breath group determination.     

Generalization to unfamiliar talkers in artificial language learning

While there is evidence that talker-specific details are encoded in the phonetics of the lexicon (Kraljic, Samuel, & Brennan, Psychological Science 19(4):332–228, 2008; Logan, Lively, & Pisoni, Journal of the Acoustical Society of America, 89(2):874-886, 1991) and in sentence processing (Nygaard & Pisoni, Perception & Psychophysics, 60(3):355–376, 1998), it is unclear whether categorical linguistic patterns are also represented in terms of talker-specific details. The present study provides evidence that adult learners form talker-independent representations for productive linguistic patterns. Participants were able to generalize a novel linguistic pattern to unfamiliar talkers. Learners were exposed to spoken words that conformed to a pattern in which vowels of a word agreed in place of articulation, referred to as vowel harmony. All items were presented in the voice of one single talker. Participants were tested on items that included both the familiar talker and an unfamiliar talker. Participants generalized the pattern to novel talkers when the talkers spoke with a familiar accent (Experiment 1), as well as with an unfamiliar accent (Experiment 2). Learners showed a small advantage for talker familiarity when the words were familiar, but not when the words were novel. These results are consistent with a theory of language processing in which the lexicon stores fine-grained, talker-specific phonetic details, but productive linguistic processes are subject to abstract, talker-independent representations.     

A comparison of hemispheric asymmetries in speech-related brain potentials of autistic and dysphasic children

In a previous study (G. Dawson, C. Finley, S. Phillips, & L. Galpert, 1986, Child Development, 57, 1440-1453) it was found that measures of hemispheric asymmetry during speech processing were predictive of level of language ability in autistic children. The purpose of the present study was to determine whether a similar relationship between pattern of hemispheric asymmetry and language ability exists for language-impaired children without autism. Ten autistic children (8-13 years), 10 dysphasic children (6-15 years), and 10 normal children (8-13 years) were compared in terms of their patterns of hemispheric asymmetry in the averaged cortical evoked response to a simple speech stimulus, and the relationship between pattern of hemispheric asymmetry and language ability was assessed for each clinical group. It was found that, for both the autistic and dysphasic groups, the majority of subjects showed a reversed direction of hemispheric asymmetry from that characteristic of the normal group. A strong relationship between pattern of asymmetry and level of language ability was found for autistic subjects; autistic subjects with more severe language impairments were more likely to show reversed asymmetry than subjects with less severe language impairments. In contrast, no relationship between language ability and direction of hemispheric asymmetry in the evoked response was found for dysphasic subjects. Separate analyses of right and left hemisphere evoked responses indicated that language ability was related to right hemisphere activity for autistic subjects, and to left hemisphere activity for dysphasic subjects.     

Tachistoscopic software for the Hercules display controller

The functions necessary for a high-quality microcomputer emulation of a tachistoscope are summarized. A software package containing an extensive set of tachistoscope-emulation functions for IBM PC-type computers is described. This software gives computers equipped with the Hercules monochrome/graphics display controller the ability to produce fast tachistoscopic presentations of text material.     

An oscilloscopic point-plotter interface for 8-bit microcomputers

An inexpensive interface capable of driving high-resolution point-plotting systems is described. Specific examples of modifications to the electronic hardware are detailed for the Rockwell Aim 65, but the design is readily adaptable to most commercially available 8-bit microcomputers. Some comparisons are drawn between salient features of raster-scan and of point-plotting display systems.     

Microcontrolled stepping motors in behavior research: Two application examples

An inexpensive microprocessor-based motor controller is described. Two examples of research applications are discussed, and a listing of a motor control program is included. Some comparisons are made between the conventional methods of laboratory motion control and the microcontrolled stepping motor approach.