Temporal summation of 500-Hz tones and octave-band noise bursts in infants and adults

A visually reinforced operant procedure was employed to obtain 2-point threshold-duration functions in 7-month-old infants and adults in two experimental paradigms. In Experiment 1, thresholds were determined for 10- and 100-msec, 500-Hz tones and octave-band noise bursts presented in quiet and noise backgrounds. Threshold-duration functions were significantly steeper for infants than for adults under all experimental conditions, and did not differ in slope as a result of differences in either stimulus bandwidth or masking noise. In Experiment 2, thresholds for trains of brief 500-Hz tone pulses were examined in infant and adult subjects. Infant functions were adult-like for integration of multiple-pulse stimuli, suggesting that the traditional, long-term process of temporal summation is mature by 7 months of age. Differences between the present results and those previously obtained for 4-kHz stimuli appear to be consistent with the view that different mechanisms are involved in the detection of low- and high-frequency signals.     

Developmental changes in infants' sensitivity to octave-band noises

Localization responses to octave-band noises with center frequencies at 200, 400, 1000, 2000, 4000, and 10,000 Hz were obtained from infants 6, 12, and 18 months of age. During an experimental trial, an octave-band noise was presented on one of two speakers located 45° to each side of the infant. A head turn to the noise (correct response) was rewarded by activating an animated toy on top of the speaker. The intensity of the noise was varied over trials (method of constant stimuli) to determine thresholds at each center frequency. Thresholds for the lower frequencies were approximately 5–8 db higher in the 6-month-old infants compared to the older infants. However, there were no consistent differences among groups at the higher frequencies. Infant thresholds were found to be 20–30 db higher than adult thresholds at the lower frequencies. At the higher frequencies thresholds for infants were approaching those of adults.     

A further study of melodic channeling

Subjects listened to repetitive presentations of C major scale patterns and simple two-part contrapuntal specimens, both dichotically and in a stereophonic free sound field. All scalar and melodic patterns were presented so that successive tones alternated from ear to ear: when a component of one scale or melody was routed through one speaker or headphone, the concurrent member of the other scale or melodic pattern was routed through the other speaker or headphone, and vice versa. The stimulus parameters of spectral contour and envelope characteristics, duration, melodic pattern, and loudness were varied, and a testing procedure was designed to minimize any bias in responses which might be produced by learning, immediate memory, or vocal Limitations of subjects. Virtually all responses (95.2% to scalar stimuli, 99.1% to melodic stimuli) indicated that the subjects channeled stimuli by pitch range, and not by ear of input. When spectral contours routed through the separate headphones or speakers were noticeably dissimilar, no subject perceived that this timbral inequality switched from ear to ear: all subjects heard an overall change in tone quality which pervaded both scalar or melodic sequences, and which apparently emanated from both headphones or speakers.     

Developmental changes in visual scanning of face and nonface patterns by infants

The eye movements of infants, aged 4–5, 7–8, and 10–11 weeks, were recorded while they viewed either a representation of a face or a nonface stimulus. Presentation of the visual stimulus was paired with the presentation of an auditory stimulus (either voice or tone) or silence. Attention to the visual stimulus was greater for the older two groups than for the youngest group. The effect of the addition of sound was to increase attention to the visual stimulus. In general, the face was looked at more than the nonface stimulus. The difference in visual attention between the face and the nonface stimulus did not appear to be based solely on the physical characteristics of the stimuli. A sharp increase in the amount of looking at the eyes of the face stimulus at 7–8 weeks of age seemed to be related to a developing appreciation of the meaning of the face as a pattern.     

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.     

Effects of sound frequency on behavioral and cardiac orienting in newborn and five-month-old infants

Alert newborn and 5-month-old infants' responsivity to variations in spectral composition of a rattle sound was examined. Each child received four stimulus conditions: low-, mid-, and high-frequency bandpass-filtered rattles and an unfiltered broadband rattle. Stimuli were played through a single loudspeaker laterally positioned, and head orientation and cardiac responses to sound were recorded. Compared to other stimuli, the low-frequency sound elicted less head turning in both age groups, with this effect exaggerated in younger infants. Head orientation toward the mid-frequency, high-frequency, and broadband stimuli did not differ with age. For all conditions, latency and duration of newborns' head turning was longer than that of 5-month-olds. Newborns responded with cardiac deceleration only on trials when they failed to turn. When head turns occurred, an acceleratory cardiac response was obtained. Five-month-olds responded with reliable cardiac deceleration irrespective of head turning toward the sound. Heart rate change did not vary as a function of frequency at either age, suggesting that all stimuli were equally effective in eliciting the infant's attention.     

Stimulus sequence and the exponent of the power function for loudness

In two experiments, 15 and 13 subjects estimated the loudness of 12 sound-pressure levels (38-104 dB; 6-dB intervals) of a 1000-Hz tone by the method of magnitude estimation with a modulus assigned to the first stimulus presented. The tone duration was 1 sec. and the interstimulus interval was 6 sec. The presentation order was systematically ascending-descending in one experiment and balanced-irregular in the other. The results indicate that (1) loudness is a power function of sound pressure with an exponent of 0.60 for the systematic order and 0.29 for the irregular order. (2) For both the irregular and systematic orders, a large step-size (12 or 18 dB) between the stimulus on Trial n and on Trial n-1 (or n-3) results in a slight assimilation effect. This also occurs for the small step-size (6 dB) in the irregular order. (3) The size of momentary exponents (based on two points, Trials n and n-1 or n-3) depends on the sound pressures of successive stimuli, whether the steps are positive or negative, and whether the stimuli have been presented in systematic or irregular order. For positive steps, the momentary exponent is lower for a soft tone (Trial n) than for a loud tone, whereas for negative steps the momentary exponent is lower for a loud tone than for a soft tone. These effects ar more pronounced when these stimuli are presented in an irregular order. A relative judgment model is offered for magnitude estimation. It assumes that subjects judge the loudness of a stimulus in terms of three reference markers: the minimum and maximum sound pressures as well as the sound pressure of the previous stimulus.     

Reliability of electrodermal habituation measures under two conditions of stimulus intensity

The present study investigated test-retest reliability of habituation of the evoked skin conductance response. Subjects received 20 presentations of a 1000-Hz, 3-sec tone at the same time of day on two separate occasions, separated by an interval of 97–160 days. Thirteen subjects received stimuli of 90 dB, while for 24 subjects, stimulus intensity was 70 dB. Interstimulus interval was 21 sec for both groups. Both absolute rate of habituation and trials to criterion displayed moderate reliability, and the relationships between habituation measures and other aspects of electrodermal activity were in agreement with previous findings.     

The effect of skin temperature on vibrotactile sensitivity

The effect of skin temperature on detection of vibrotactile stimuli was measured for vibrations of 30 and 250 Hz. Data for the 250-Hz stimulus supported the results of Weitz (1941), who found that thresholds for 100-, 256-, and 900-Hz vibration varied as a If-shape function of skin temperature with a minimum at about 37°C. Temperature had a negligible effect on sensitivity at 30 Hz. A second experiment examined a range of frequencies between 30 and 250 Hz. Cooling greatly lowered sensitivity only to 150- and 250-Hz stimuli. Warming reduced sensitivity less, but more uniformly across frequencies. It was concluded that cooling may affect vibrotactile thresholds by decreasing the sensitivity of Pacinian corpuscles; the reason for the decrease in sensitivity due to warming is unclear.     

Twelve-month-olds privilege words over other linguistic sounds in an associative learning task

We examined whether 12-month-old infants privilege words over other linguistic stimuli in an associative learning task. Sixty-four infants were presented with sets of either word–object, communicative sound–object, or consonantal sound–object pairings until they habituated. They were then tested on a ‘switch’ in the sound to determine whether they were able to associate the word and/or sound with the novel objects. Infants associated words, but not communicative sounds or consonantal sounds, with novel objects. The results demonstrate that infants exhibit a preference for words over other linguistic stimuli in an associative word learning task. This suggests that by 12 months of age, infants have developed knowledge about the nature of an appropriate sound form for an object label and will privilege this form as an object label.     

Infants’ detection of increments in low- and high-frequency noise

A visually reinforced operant paradigm was employed to examine the relationship between the difference limen (DL) for intensity and level of the standard during infancy. In Experiment 1,7-month-old infants and adults detected increments in continuous noise presented via headphones at each of four levels ranging from 28 to 58 dB SPL. Noise stimuli were 2-octave bands centered at either 400 or 4000 Hz, and increments were 10 and 100 msec in duration. Infants’ DLs were significantly larger than those of adult subjects and significantly larger for low- than for high-frequency stimuli. For the high-frequency noise band, infants’ DLs were generally consistent with Weber’s law,remaining essentially constant for standards higher than 28 dB SPL (3 dB SL) for 100-msec increments and 38 dB SPL (13 dB SL) for 10-msec increments. For low-frequency noise, infants’ absolute thresholds were exceptionally high, and sensation levels of the standards were too low to adequately describe the relationship. In Ex-periment 2, 7-month-old infants detected 10- and 100-msec increments in 400-Hz noise stimuli presented in sound field. Infants’ low-frequency DLs were large at low intensities and decreased with increases in level of the standard up to at least 30 dB SL. For both low- and high-frequency noise, the difference between DLs for 10- and 100-msec increments tended to be large at low levels of the standard and to decrease at higher levels. These results suggest that the relationship between the DL and level of the standard varies with both stimulus frequency and duration during infancy. However, stimulus-dependent immaturities in increment detection may be most evident at levels within approximately 30 dB of absolute threshold.     

Development of neuronal responsiveness in the mediorostral neostriatum/hyperstriatum ventrale during auditory filial imprinting in domestic chicks

Chronic electrophysiological recordings of slow field potentials from tone-imprinted chicks show significantly enhanced fast Fourier transform (FFT) power during playback of rhythmic 400-Hz imprinting tone stimuli in the presence of a surrogate mother. The FFT power was already significantly higher during the very first imprinting session, when the chick was exposed to the imprinting tone stimuli in the presence of the surrogate mother compared to spontaneous activity (EEG recordings). During discrimination tests, where individual chicks were exposed to the imprinting tone stimuli in alternation to rhythmic 700-Hz tone stimuli (discrimination tone stimuli), the FFT power was significantly higher during playback of the imprinting tone stimuli than the FFT power during playback of the discrimination tone stimuli. Chicks which were imprinted in the absence of the surrogate mother also show enhanced FFT power in the course of the imprinting sessions; however, in contrast to the first group, they did not show significant differences in the FFT power during playback of either the imprinting or discrimination tone stimuli in the discrimination tests. Our results suggest that the high FFT power of a potential imprinting stimulus or situation, which is expressed in newborn (still naive) chicks, is maintained only when the chicks form an association between the tone stimuli and a positive emotional situation (represented by the surrogate mother).     

Memory retrieval by 18--30-month-olds: age-related changes in representational flexibility

Deferred imitation was used to trace changes in memory retrieval by 18-30-month-olds. In all experiments, an adult demonstrated 2 sets of actions using 2 different sets of stimuli. In Experiments 1A and 1B, independent groups of infants were tested immediately or after a 24-hr delay. Each infant was tested with 1 set of stimuli from the original demonstration and 1 set of stimuli that was different. Recall of the target actions when tested with different stimuli increased as a function of age, particularly after a delay. In Experiment 2, infants were provided with a unique verbal label for the stimuli during the demonstration and the test. The verbal label facilitated performance by 24-month-olds tested with different stimuli but had no effect on performance by 18-month-olds. One hallmark of memory development appears to be an age-related increase in the range of effective retrieval cues for a particular memory.     

Auditory sensitivity and tone-sequence reproduction in oral contraceptive users and nonusers

In two stages spanning a single academic year, 10 women using oral contraceptives and 11 not using oral contraceptives were tested on their auditory threshold sensitivity to six frequencies (250, 750, 1500, 3000, 6000, and 8000 Hz) as a function of phases of the menstrual cycle. 11 women (5 users and 6 nonusers) were also tested on their ability to reproduce successively longer tone sequences. Results showed that there was little variation due to phase of the menstrual cycle, with the exception that oral contraceptive users showed lower relative thresholds at low frequencies during the postmenstrual phase. Over-all, oral contraceptive users had higher absolute and relative thresholds than nonusers, except at 3000 Hz. Although not statistically significant, results on the tone-reproduction test showed an enhanced ability to reproduce tones during the premenstrual phase for women using oral contraceptives. Results are discussed in relation to previous findings.     

The effects of sound duration on newborns' head orientation

Two experiments assessed the importance of sound duration for eliciting head orientation responses from newborn infants. In Experiment 1, thirty infants turned with equal frequency toward 20-s continuous rattle sounds and 20-s trains of rattle segments. The duration of the rattle segments--14 and 100 ms (2/s), or 500 ms (1/s)--did not influence the likelihood of turning. Response latencies and durations proved quite similar for all stimuli. In Experiment 2, twenty-four infants heard continuous rattle sounds of four different durations: 1, 5, 10, and 20 s. They turned reliably to all stimulus durations; furthermore, the magnitude and temporal characteristics of head orientation responses did not differ for the four stimulus durations. These results suggest that the newborn's head orientation response may reflect a motor program that is initiated by auditory input and then executed in a similar fashion regardless of further stimulation.     

Influences of vowel and tone variation on emergent word knowledge: a cross‐linguistic investigation

To learn words, infants must be sensitive to native phonological contrast. While lexical tone predominates as a source of phonemic contrast in human languages, there has been little investigation of the influences of lexical tone on word learning. The present study investigates infants’ sensitivity to tone mispronunciations in two groups of infants. For one group (Chinese learners), tone is phonemic in their native language, and for the second group (English learners), tone is non‐phonemic and constituted suprasegmental variation. In Experiment 1, English learners were trained on novel word–object pairings and tested on their recognition of correct pronunciations, tone and vowel mispronunciations of these words at 18 and 24 months. In Experiment 2a, bilingual English‐Chinese learners were tested on a similar task translated into Chinese at the same age intervals. Results demonstrate that non‐tonal learners treated tonal and vowel substitutions alike as mispronunciations at 18 months but only treated vowel substitutions as mispronunciations at 24 months. Tonal learners treated both tonal and vowel substitutions as mispronunciations at both ages. In Experiment 2b, bilingual non‐tone language learners were tested on the same set of tasks replicating a similar set of results as monolingual non‐tone language learners (Experiment 1). Findings point to an early predisposition to treat tone as a defining characteristic of words regardless of its lexical relevance at 18 months. Between 18 and 24 months, learners appear to ascribe lexical relevance to tone in a language‐specific manner. The current study identifies the influences of tone variation on memories for newly learned words and the time period during which lexical tone – a highly frequent constituent of human languages – actually becomes lexical for early learners. Findings are contextualized with prevailing models of the developing lexicon.     

Directed attention influences the modification of startle reflex probability

The present study was designed to investigate the effect of directed attention on elicitation and modification of the startle reflex. 30 adult human subjects received 90 dB(A) broadband noise startle stimuli either alone or preceded by a 60 dB(A) prepulse (either 2000-Hz tone, 1000-Hz tone, or broadband noise). Subjects were instructed to attend to one of the three prepulses during half the trials and to ignore all stimuli during the rest of the trials. The probability of responding while attending to a prepulse was significantly lower than the probability of responding while ignoring the prepulses. Responding to the prepulses was also more probable while subjects were attending to the prepulses, and these effects were more pronounced for tone than for noise prepulses. These results suggest that directed attention can influence the probability of the startle reflex without influencing startle amplitude or latency.     

Infant perception of causal motion produced by humans and inanimate objects

Both the movements of people and inanimate objects are intimately bound up with physical causality. Furthermore, in contrast to object movements, causal relationships between limb movements controlled by humans and their body displacements uniquely reflect agency and goal-directed actions in support of social causality. To investigate the development of sensitivity to causal movements, we examined the looking behavior of infants between 9 and 18 months of age when viewing movements of humans and objects. We also investigated whether individual differences in gender and gross motor functions may impact the development of the visual preferences for causal movements. In Experiment 1, infants were presented with walking stimuli showing either normal body translation or a “moonwalk” that reversed the horizontal motion of body translations. In Experiment 2, infants were presented with unperformable actions beyond infants’ gross motor functions (i.e., long jump) either with or without ecologically valid body displacement. In Experiment 3, infants were presented with rolling movements of inanimate objects that either complied with or violated physical causality. We found that female infants showed longer looking times to normal walking stimuli than to moonwalk stimuli, but did not differ in their looking time to movements of inanimate objects and unperformable actions. In contrast, male infants did not show sensitivity to causal movement for either category. Additionally, female infants looked longer at social stimuli of human actions than male infants. Under the tested circumstances, our findings indicate that female infants have developed a sensitivity to causal consistency between limb movements and body translations of biological motion, only for actions with previous visual and motor exposures, and demonstrate a preference toward social information.     

Children's scales of length and loudness: A developmental application of cross-modal matching

The cross-modal matching techniques that have produced scales of sensory magnitude for a variety of perceptual continua in adults were used to construct similar scales in children. Subjects were adults and children 4, 6, 8, and 12 years old. Their task was, first, to match the loudness of a 1000-Hz tone to various visual lengths, and, second, to match the length of a white tape to various loudnesses of the tone. Almost all subjects were able to perform the matching tasks; the average precision of older subjects (12 and Adult) was somewhat greater, but in each of the younger age groups a majority of subjects performed with a precision that equaled that of older subjects. The exponent of the power function that relates length and loudness does not change with age. The scale factor does change, in a way that suggests either that a given sound intensity seems softer, or, more probable, that a given length seems longer, to younger children. The success of cross-modal matching with subjects as young as 4 years means that it is possible to investigate not only single perceptual scales but also intermodal organization in young children.     

Neuroanatomical basis of binaural phase-difference analysis for sound localization: a comparative study.

Four varieties of mammals whose medial superior olives range from large to none at all were tested for their ability to localize single, brief tone pips at various frequencies. Although each animal could localize high-frequency tone pips, their ability to localize middle- and low-frequency tone pips corresponded to the size of their medial superior olive (MSO). Since this latter range of frequencies is the one in which binaural phase-difference cues predominate, this anatomical-behavioral correspondence supports the idea that MSO is the chief binaural time-analyzing center for sound localization.