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Biomedical subjects

L A Thorpe

Publications and source records attributed to L A Thorpe.

12 recordsLinked to original sources
PubMed1990

Infants' perception of timbre: classification of complex tones by spectral structure.

Infants 7 to 8.5 months of age were tested for their discrimination of timbre or sound quality differences in the context of variable exemplars. They were familiarized with a set of complex tones with specified spectral structure; members of the set varied in fundamental frequency, intensity, or duration. Infants were then tested for their detection of tones that contrasted in spectral structure but were similar in other respects. They successfully differentiated the two spectral structures in the context of these variations, indicating that they can classify tonal stimuli on the basis of timbre. When the stimuli were organized into arbitrary categories, infants were unable to differentiate these categories, indicating that their performance with nonarbitrary categories was not attributable to memorization of the familiarized set.

Female↗
PubMed1989

Infants' perception of rhythm: categorization of auditory sequences by temporal structure.

We presented 7- to 9-month-old infants with repetitions of three- or four-tone sequences characterized by a particular rhythmic structure. We then evaluated their detection of changes in rhythmic structure in the context of randomly presented variations in tempo (rate) and frequency. Infants successfully differentiated between three-tones sequences with 1, 2 (X XX) and 2, 1 (XX X) structure as well as four-tone sequences with 2, 2 (XX XX) and 3, 1 (XXX X) structure. In other tasks, they indicated their ability to discriminate between contrasting tempos in the context of frequency variations. We conclude, then, that infants can categorize auditory sequences on the basis of rhythm and also on the basis of tempo.

Arousal↗
PubMed1989

Developmental changes in masked thresholds.

Masked thresholds for octave-band noises with center frequencies of 0.4, 1, 2, 4, and 10 kHz and for a 1/3-octave-band noise centered at 10 kHz were obtained from listeners 6.5 months to 20.5 years of age at two levels of a broadband masker (0 and 10 dB/cycle). Thresholds declined exponentially as a function of age for all stimuli tested. The rate and extent of this decline, but not its asymptote, were independent of the frequency or bandwidth employed. The time course for this change parallels that found for electrophysiological maturation of more central auditory processes.

Adolescent↗
PubMed1989

Developmental changes in high-frequency sensitivity.

Sensitivity to 1/3-octave-band noises with centre frequencies of 10, 20, and 25 kHz was measured for 200 children between 1.5 and 16 years of age and for 20 young adults. In the case of the 25-kHz signal, listeners of 1.5 and 3 years of age as well as those 16 and 20 years of age were unable to detect it at its highest intensity (57 dB). In contrast, listeners 5-14 years of age could detect the 25-kHz signal. Sensitivity to the 20-kHz signal improved until about 8 years of age, deteriorating gradually thereafter. Finally, sensitivity to the 10-kHz signal improved rapidly, reaching young adult levels by 5 years of age, and remaining stable until 20 years of age. These findings are consistent with the onset of high-frequency hearing losses at around 10 years of age. Whether such hearing losses are due to normal aging (presbyacusis) or to noise exposure (socioacusis) remains to be determined.

Adolescent↗
PubMed1989

Effects of uncertainty on melodic information processing.

In three experiments, musically trained and untrained adults listened to three repetitions of a 5-note melodic sequence followed by a final melody with either the same tune as those preceding it or differing in one position by one semitone. In Experiment 1, ability to recognize the final sequence was examined as a function of redundancy at the levels of musical structure in a sequence, contour complexity of transpositions in a trial, and trial context in a session. Within a sequence, tones were related as the major or augmented triad; within a trial, the four sequences began on successively higher notes (simple macrocontour) or on randomly selected notes (complex macrocontour); and within a session, trials were either blocked (all major or all augmented) or mixed (major and augmented randomly selected). Performance was superior for major melodies, for systematic transpositions within a trial (simple macrocontours), for blocked trials, and for musically trained listeners. In Experiment 2, we examined further the effect of macrocontour. Performance on simple macrocontours exceeded that on complex, and excluded the possibility that repetition of the 20-note sequences provided the entire benefit of systematic transposition in Experiment 1. The effect of musical structure (major/augmented) was also replicated. In Experiment 3, listeners provided structure ratings of ascending 20-note sequences from Experiment 2. Ratings on same trials were higher than those on corresponding different trials, in contrast to performance scores for augmented same and different trials in previous experiments. The concept of functional uncertainty was proposed to account for recognition difficulties on augmented same trials. The significant effects of redundancy on all the levels examined confirm the utility of the information-processing framework for the study of melodic sequence perception.

Adolescent↗
PubMed1988

Auditory sensitivity in school-age children.

Thresholds for octave-band noises with center frequencies of 0.4, 1, 2, 4, and 10 kHz and 1/3-octave-band noises centered at 10 and 20 kHz were obtained from children 6 to 16 years of age. Such thresholds, combined with those obtained previously for infants, preschool children, and adults, provide a detailed picture of developing auditory sensitivity between infancy and maturity. Continuing improvements in sensitivity are evident from infancy through the preschool period, well into the school years. For stimuli with center frequencies of 0.4 and 1 kHz, maximal sensitivity is achieved at about 10 years of age, compared to 8 years for stimuli of 2 and 4 kHz. For 10-kHz stimuli, there is little change beyond 4 or 5 years of age. Finally, 20-kHz stimuli yield maximal sensitivity at about 6 or 8 years of age, followed by a progressive decline to adult levels. These findings are considered in relation to auditory sensitivity in nonhuman species, to structural and functional development of the ear, and to possible changes in the efficiency of neural processing.

Adolescent↗
PubMed1987

Organizational processes in infants' perception of auditory patterns.

Infants 9-11 months of age were tested for their discrimination of changes in the melodic contour (direction of successive pitch changes) of brief melodies in the context of discernible variations in key (different absolute frequencies, same intervals) or interval size (different absolute frequencies and frequency ratios, same contour). Infants detected contour changes in both variable contexts, suggesting that they categorize sequences of sounds on the basis of global, relational properties such as melodic contour. Implications of such processing strategies for infants' perception of running speech are considered.

Attention↗
PubMed1987

Deaf children's referential messages to mother.

Deaf children 6-10 years of age, from oral or bimodal educational programs, were tested in 2 tasks. In the first, they were required to describe a designated picture from a set of 4 pictures so that their mother could identify the intended referent from the 4 alternatives. In the second, they studied a single picture and were subsequently required to identify it from a set of 4 related pictures. Despite greater hearing loss, bimodally educated children provided more differentiated messages than did orally educated children. Bimodally educated children also provided better reformulations of messages that were initially inadequate. Although mothers of orally educated children received inferior messages, they were as successful at selecting the correct referent as were mothers of bimodally educated children. Both groups of deaf children performed at near perfect levels on the picture recognition task, suggesting that performance differences were attributable to differential message formulation skill as opposed to differential visual processing of the referential array.

Child↗
PubMed1986

Development of the perception of musical relations: semitone and diatonic structure.

In the present research we examined the development of sensitivity to two musical relations significant in Western tonal music, the semitone and diatonic structure. Infants and preschool children were tested for their detection of a semitone change in any position of a five-note melody. Two standard melodies were used, one composed of diatonic tones only and the other containing a non-diatonic tone. In Experiment 1, children from 4 to 6 years of age were superior in detecting the semitone change in the diatonic context compared with the nondiatonic context. In Experiment 2, infants 9 to 11 months of age detected the semitone change in all positions, but their performance was not influenced by diatonic context. These findings indicate that infants and children can discriminate a semitone in a musical context and that the priority of diatonic structure emerges by 4 to 6 years of age.

Auditory Perception↗
PubMed1986

Auditory sensitivity in preschool children.

Thresholds for octave-band noises with center frequencies of 0.4, 1, 2, 4, and 10 kHz, and 1/3-octave-band noises with center frequencies of 10 and 20 kHz, were obtained from children 3-5 years of age and from a comparison group of adults. Thresholds for all frequencies decreased between 3 and 5 years of age. Thresholds decreased further between 5 years of age and adulthood, except for the 20-kHz stimulus, for which children had lower thresholds than adults. These results are discussed in terms of possible age-related changes in the mechanical properties of the ear and in the efficiency of neural coding.

Adolescent↗
PubMed1985

Children's perception of melodies: the role of contour, frequency, and rate of presentation.

Children 4 to 6 years of age were exposed to repetitions of a six-tone melody, then tested for their detection of transformations that either preserved or changed the contour of the standard melody. Discrimination performance was examined as a function of contour condition, magnitude of contour change, rate of presentation, and the presence of novel frequencies. Performance was superior for transformations that changed contour compared to those that did not, for greater changes in contour, and for faster presentation rates. Melodies transformed by a reordering of component tones were no less discriminable than those transformed by the addition of novel frequencies.

Auditory Perception↗