Lynne Werner Olsho

Pure‐tone sensitivity of human infants

Pure-tone thresholds at frequencies ranging from 250 to 8000 Hz were estimated for 3-, 6-, and 12-month-old infants and for adults, using the Observer-based Psychoacoustic Procedure (OPP). Sounds were presented monaurally using an earphone. Psychometric functions of infants were similar to those of adults, although 3-month-olds had shallower functions at higher frequencies. The thresholds of 6- and 12-month-old infants were 10-15 dB higher than those of the adults, with the difference being greater at lower frequencies. This result is in general agreement with results from other laboratories. The thresholds of 3-month-olds were 15-30 dB higher than those of adults. The greatest difference between 3-month-olds and adults was at 8000 Hz. This threshold difference is smaller than that reported in earlier behavioral studies; higher thresholds at high frequencies have been previously reported for newborn and 3-month-old infants. The relative contributions of sensory and nonsensory variables to these age differences are discussed.

Level and age effects in infant frequency discrimination

Frequency difference limens (FDLs) were estimated for 3-, 6-, and 12-month-old infants and for adults using pure tones at 500, 1000, and 4000 Hz. Each listener provided an FDL at 40 dB and at a higher (80 dB, in most cases) sensation level (SL). An observer-based behavioral testing technique was used. The FDLs of 3-month-olds were worse than those of adults at all three frequencies, and increased with increasing frequency. The FDLs of 6- and 12-month-olds were worse than those of adults at 500 and 1000 Hz, but not at 4000 Hz. Decreasing the SL led to an increase in the FDL of about the same magnitude at all ages, and the same age differences were found at both SLs. Thus infant-adult differences in FDL are not a simple consequence of differences in absolute sensitivity. Infant FDLs at one SL were also found to be significantly correlated with the FDL at the other SL. The FDLs at one age were, in general, predictive of the FDL at a later age in a longitudinal sample of infants. Models that might account for these age-related differences are discussed.

Auditory Frequency Discrimination in Infancy

The ability of 5-8-month-old infants and of young adults to detect changes inthe frequency of pure tones was investigated. A head turn for visual reinforcementtechnique was used to obtain difference thresholds for 14 infants and 5 adultsat 1000, 2000, and 3000 Hz. With signals presented at 70 dB above adultdetection thresholds, infants reliably detected frequency changes on the orderof 2%, whereas adults could detect changes of about 1%. These data not onlyconfirm the findings of previous, studies that infants can distinguish differentfrequencies but indicate that infants can make relatively fine discriminations.

Discharge patterns of lagenar and saccular neurones of the goldfish eighth nerve: Displacement sensitivity and directional characteristics

Abstract 1. 1. The responses of goldfish lagenar and saccular neurones were analyzed for underwater sound stimulation and head vibration in three orthogonal directions. 2. 2. Both organs show similar sound pressure and displacement sensitivity below 200 Hz, and respond to a motional stimulus component at 100 Hz. 3. 3. Calculated directions of best sensitivity in the saggital and horizontal planes correspond with hair cell orientation maps. 4. 4. Stimulus-response phase-angles correspond only roughly with the patterns to be expected from a simple model for hair cell stimulation. 5. 5. Variation in the degree of coupling between hair cell cilia and the otolith, and complex three-dimensional relative motion patterns probably occur in both organs.

Infant frequency discrimination

Frequency difference limens were determined for infants aged 5 to 8 months and for adults, at six tonal frequencies ranging from 250 to 8000 Hz, using the visually reinforced head-turn procedure. The relative difference threshold (threshold divided by frequency) was a nonmonotonic function of frequency with a minimum around 1000 Hz for both infants and adults. However, infant thresholds were twice those of adults at low frequencies but did not differ from adult values at high frequencies. Previously reported differences in absolute sensitivity at low frequencies are not great enough to account for the age difference in low frequency discrimination ability. These findings suggest that the auditory mechanisms responsible for frequency discrimination mature first at high frequencies, paralleling the base to apex sequence of prenatal development of hair cells and associated auditory nerve fibers.

Preliminary data on frequency discrimination in infancy

An operant head‐turn technique was used to measure frequency‐difference thresholds for 5‐ to 8‐month old infants and for adults. At a standard of 1000 Hz, presented at 70 dB above adult threshold, infant thresholds averaged 21.6 Hz, adult thresholds, 7.4 Hz. In a two‐alternative forced choice procedure, difference thresholds of the same adults approached those reported by Wier et al. [J. Acoust. Soc. Am. 61, 178–184 (1977)].

Response patterns of neurons in the lagenar branch of the goldfish auditory nerve

The response of single fibers of the goldfish lagenar nerve were recorded extracellularly in response to tonal stimuli generated by a loudspeaker. Measures were made of both the average impulse rate and the degree of phase locking at a number of different stimulus frequencies and sound pressure levels. Phase locking was determined to be a more sensitive and reliable measure of sound pressure sensitivity than impulse rate. Unit tuning curves constructed using phase‐locking criteria showed low‐pass characteristics above 150 Hz. Wide variability was observed in sensitivity, bandwidth, spontaneous activity and adaptation. Lagenar fibers overlap in sensitivity with type II saccular neurons described by Fay [J. Acoust. Soc. Am. 60, S80 (A) (1976)]. The discharge patterns of lagenar and saccular neurons were analyzed in response to direct vibration of the head and were found to have quite similar directional sensitivities. The results are discussed in terms of the information available to the fish for auditory l...

Infant thresholds for short duration tone bursts

Thresholds for short duration tone bursts were measured for three‐and six‐month‐old infants and for adults. An experimenter, blind to trial type, observed the infants behavior. On each trial, the experimenter judged whether or not a tone had been presented and received feedback. The stimuli were 1000‐Hz pure tones, with 16‐ms rise/fall times and no steady‐state duration. Eight tone bursts were presented at a rate of 2/s during a signal trial. Stimuli were presented monaurally via insert earphone. Thresholds were estimated using an adaptive procedure. Adults were tested using the same stimuli and procedure. Thresholds for six‐month‐olds averaged about 13 dB higher, while those of three‐month‐olds averaged about 24 dB higher than those of the adults. The size of the infant‐adult difference for these short duration tones is nearly the same as that reported for longer duration stimuli [Olsho et al., J. Acoust. Soc. Am. Suppl. 1 80, S123 (1986)]. That the effects of duration on detection threshold are quite s...

SEARCHING FOR MULTIPLE TARGETS SIMULTANEOUSLY: IS IT REALLY POSSIBLE?

In an attempt to clarify the findings of Neisser and his associates with respect to parallel processing of multiple target items in a visual search task, subjects were tested in a multiple-target search situation in which the various target sets were not nested. 20 sessions were run for each subject with 12 trials per day. The targets used were geometric forms, allowing for manipulation of the number of features in each form. The results do not confirm those of Neisser, in fact, the interaction of session × target-set size was in a direction opposite to that predicted by a parallel scan model. These findings indicate that what Neisser reported as parallel preattentive processing may in fact have reflected a tendency for subjects to scan for a master set of targets, regardless of which subset of that set was actually present on a given set.

Foveal task effects on same-different judgments in the visual periphery

An attempt was made to examine the extent to which the presence of a foveal stimulus affects same-different judgments regarding the horizontal-vertical orientation of two lines located in peripheral vision. The results of the study indicated that accuracy in reporting peripheral visual stimuli is determined not only by the nature of those stimuli, but also by whether other stimuli are presented foveally. The simultaneous presence of another stimulus in foveal vision reduces accuracy in reporting peripheral stimuli, independent of instructions to ignore, detect, or identify the foveal stimulus.