Biomedical subjects

L A Werner

Publications and source records attributed to L A Werner.

3 recordsLinked to original sources

PubMed1992

Infant auditory temporal acuity: gap detection.

The development of auditory temporal acuity during infancy was examined in 3-, 6-, and 12-month-old infants and in adults using the gap detection paradigm. Listeners detected a series of gaps, or silent intervals, or variable duration in a broadband noise. In order to vary the acoustic frequencies available to the listener, a high-pass noise was used to mask frequencies above specified cutoffs. High-pass maskers with cutoffs of 500, 2,000, and 8,000 Hz were used. The minimum detectable gap was determined using the Observer-based Psychoacoustic Procedure. The thresholds of 3- and 6-month-olds were considerably poorer than those of the adults, although the effect of masker condition was about the same for these 3 groups. The thresholds of 12-month-olds were significantly worse than the adults when the stimulus was unmasked or when the masker cutoff frequency was 2,000 or 8,000 Hz. When the masker cutoff frequency was 500 Hz, 12-month-olds fell into 2 groups: some had gap thresholds that were about the same as 3- and 6-month-olds, while some had gap thresholds that approached those of adults. In a second experiment, a larger group of 12-month-olds were tested with a 500-Hz masker cutoff. Average performance of 12-month-olds was about the same as that of 3- and 6-month-olds in Experiment 1. Some infants attained thresholds close to those of adults. Thus, gap detection thresholds are quite poor in infants, although the similarity of the effect of frequency on performance in infants and adults suggests that the mechanisms governing temporal resolution in infants operate qualitatively like those in adults.

Adult↗

PubMed1991

Methods for estimating infant thresholds.

Detection thresholds for 1000-Hz, 16-ms tone bursts were estimated for 3- and 6-month-old infants and for young adults. The test procedure used was the observer-based psychoacoustic procedure. Thresholds were estimated using two different adaptive procedures and the method of constant stimuli. There was little difference among the average thresholds determined by any of these techniques. The least variable thresholds were obtained in the method of constant stimuli. In addition, 10 infants at each age completed two 30-trial blocks of trials in the method of constant stimuli; 22 adults completed 8 blocks of 30 trials. For 3- and 6-month-olds and for adults, there was no significant change in average threshold between blocks. Individual 6-month-olds' thresholds rarely changed by more than 5 dB between blocks, and the correlation between the thresholds obtained in the two blocks was significant. Individual 3-month-olds' thresholds, however, sometimes changed by as much as 10 dB between blocks, and the correlation between first and second block threshold was not significant. The effects of response bias on threshold were assessed by examining receiver operating characteristic plots of hit and false alarm rates at threshold and the correlation between false alarm rate and threshold. Although there was some variability in response bias, infant/observer teams tended to respond in an unbiased fashion. In one of the adaptive procedures only, false alarm rate was significantly correlated with threshold. In all procedures, the exclusion of infants with high false alarm rates changed the average thresholds obtained by less than 5 dB.(ABSTRACT TRUNCATED AT 250 WORDS)

Audiometry, Pure-Tone↗

PubMed1991

Sources of auditory masking in infants: distraction effects.

Previous work has demonstrated that infants' thresholds for a pure tone are elevated by a masker more than would be predicted from their critical bandwidths. The present studies explored the nature of this additional masking. In Experiment 1, detection thresholds of 6-month-old infants and of adults for a 1-kHz tone were estimated under three conditions: in quiet, in the presence of a 4- to 10-kHz bandpass noise at 40 dB SPL, and in the presence of the same noise at 50 dB SPL. The noise was gated on at the beginning of each trial. Adult thresholds were the same in all three conditions, indicating that little or no sensory masking took place in the presence of the noise. Infant thresholds were about 10 dB higher in the presence of the noise. We term this effect distraction masking. In Experiment 2, the effect of gating the noise on at trial onset was examined. Thresholds for the same tone were estimated in quiet and in the presence of the band-pass noise at 40 dB SPL, but the noise was presented continuously during the session. Under these conditions, distraction masking was still observed for infants. These findings suggest that a masker can have nonsensory effects on infants' performance in a psychoacoustic task.

Attention↗