Michael A. Hammer

Perception of gated, highly familiar spoken monosyllabic nouns by children, teenagers, and older adults

A forward-gating procedure, employing highly familiar monosyllabic words, was used in testing 5–7-year-old children, 15–17-year-old teenagers, and 70–85-year-old adults. Teenagers identified the words at shorter gate durations than either the children or older adults, whose identification performances were nearly identical. Teenagers gave meaningful guesses at shorter durations than children, who, in turn, gave meaningful guesses at shorter durations than adults. The oldest listeners provided the largest number of phonetic guesses, whereas teenagers gave almost none. Individual differences in auditory pure-tone sensitivity did not account for the results. It is hypothesized that both word frequency effects and temporal processing differences were responsible for the findings.

Age differences in discrimination of simulated single-formant frequency transitions

We studied auditory discrimination of simulated single-formant frequency transitions that resembled portions of certain speech consonants. Significant age differences in transition discrimination occurred; both children and older adults required larger acoustic differences between transitions for discrimination than did teenagers/young adults. Longer transitions were more easily discriminated than shorter transitions by all listeners, and there were no differences between discriminations of rising and falling transitions. Teens/young adults and older adults, but not children, required larger frequency differences to discriminate frequency transitions followed by a steady-state sound than for transitions alone. There were also age differences in discrimination of steady-state sounds. These developmental-perceptual differences may help explain why children and older adults who have good pure-tone sensitivity may experience difficulty in understanding speech.

Perception of Gated, Highly Familiar Spoken Monosyllabic Nouns by Children With and Without Learning Disabilities

A forward-gating procedure employing highly familiar monosyllabic words was used in auditory testing of age- and gender-matched children with learning disabilities and normally achieving children aged 8 to 11 years. The portion of the word presented, or “gate,” was longer on each successive trial. Nondisabled children identified an average of one more word than the children with learning disabilities, but the mean duration required for word identification did not differ between groups. Better receptive vocabulary scores were associated with identification of words at shorter durations only among the children with learning disabilities. The two groups of children had similar numbers of different meaningful-word and different non-word incorrect responses. The children with learning disabilities exhibited poorer fine-grained auditory discrimination than a control group of nondisabled children. The study concluded that auditory closure skills for the gating task were as good among children with learning disabilities as among nondisabled children, but that sensory discrimination problems may contribute significantly to the learning difficulties of the former group.

Discrimination of rising and falling simulated single-formant frequency transitions: practice and transition duration effects

Two experiments evaluated discrimination of simulated single-format frequency transitions. In the first experiment, listeners received practice with trial-by-trial feedback in discriminating either rising or falling frequency transitions of three different durations (30, 60, and 120 ms). Transitions either occurred in isolation or were followed by a steady-state sound matched in frequency to the transition end point. Some improvement in discrimination over practice runs occurred for the shortest transitions. Whether performance was evaluated at the beginning or end of practice, there were no differences attributable to transition direction or to whether transitions were followed by steady-state sound. Discrimination, however, was significantly better for the longest transitions. Just noticeable differences (jnds) for the longest transitions, measured in Hz at transition onsets, were of approximately the same magnitude as jnds for steady-state sounds that were equal in frequency to the midpoints of the transitions. Subjects of the second experiment discriminated the longer rising and falling transitions, but did not receive extensive practice. Results of experiment 2 replicated results of experiment 1 in showing similar jnds. Experiment 2 also showed no differences attributable to transition direction or to the presence of the steady-state sound following transitions.

Fine-grained auditory discrimination and performance on tests of receptive vocabulary and receptive language

This research investigated the relation between children’s performance on two measures of receptive language and children’s auditory discrimination of consonant-vowel sounds having frequency and temporal acoustic differences. The measures of fine-grained auditory discrimination produced significant multiple regression coefficients against both receptive vocabulary (Peabody Picture Vocabulary Test-Revised) and receptive language (Token Test for Children) scores. Validation analyses conducted by predicting receptive vocabulary and language scores for a new sample of children and relating them to the actual scores led to significant outcomes. It was concluded that fine-grained auditory discrimination is particularly important in the relatively early stages of language learning.

Asymmetrical discrimination of narrow‐band stimuli

A three-interval, forced-choice procedure that obtained complete psychometric functions was used to study frequency discrimination for 13-item continua of impulse-generated, narrow-band, buzz-like, steady-state sounds. For all subjects and durations, discrimination relative to the highest center frequency (1060 Hz) stimuli was better than discrimination relative to the lowest center frequency (940 Hz). This result is not in consonance with traditional reports of pure tone frequency discrimination and is not readily explained. However, additional experiments with similar stimuli replicated these findings.

Discrimination of second-formant-like frequency transitions

Discrimination of two types of simulated single-second-formant: frequency transitions was studied, transitions where members of a stimulus set shared the same onset frequency and transitions where stimuli of a set shared the same offset frequency. Experiment 1 employed an adaptive procedure to measure just-noticeable differences for transitions that increased in frequency. Experiment 2 obtained complete psychometric functions, based on a three-interval,forced choice procedure,for transitions that either increased or decreased in frequency. In both experiments, better discrimination occurred for longer stimuli, measured in hertz/millisecond, and for transitions that shared the same onset frequency. There were no differences, in Experiment 2, between discrimination of rising and falling transitions. Results are considered from several theoretical perspectives.

Antagonism of opiate-like, lanthanum-induced analgesia by naloxone, 2 mg/kg, in rats

Abstract Lanthanum chloride (La +3 ; 1 mol) was microcannulated into the ventral central gray of rats. The latency to tail-flick and to face-rub (both evoked by noxious heat) was elevated to about 250% of a sham control condition. Naloxone, 2 mg/kg, antagonized the analgesia, reducing the latencies to values not different, in most cases, from control values.

Discrimination of Converging and Diverging Frequency Transition

ABSTRACT Better discrimination occurred within sets of frequency transitions that diverged from a common onset frequency than among sets of transitions that converged to the same offset. No single available theory satisfactorily explains these outcomes.

Relation of children's identification of consonant‐vowel syllables to their fine‐grained auditory discrimination: A progress report

Just‐noticeable differences (JNDs) and identification (i.e., labeling) functions were obtained for children aged 6 through 11 years. Two consonant‐vowel (CV) continua representing the place‐of‐articulation and voice‐onset‐time features served as stimuli; the adaptive discrimination task that has been previously described [e.g., L. L. Elliott et al., J. Acoust. Soc. Am. 70, 669 (1981)] was used. Some children produced consistent identification functions for both continua; some were inconsistent in labeling CVs of one continuum only; and some were inconsistent for both continua. In many cases, the children with the poorest identification performance also exhibited the poorest JNDs for the same stimulus continuum. The irregular identification functions observed for some of these normal‐hearing children resembled functions that have been reported for some adults [B. E. Walden et al., J. Acoust. Soc. Am. 79, 1101 (1986)]. [Work supported, in part, by NINCDS (NIH).]