No abstract

Infants 8-11 months of age were exposed to repetitions of a 6-tone sequence or melody, then tested for their discrimination of transpositions of that sequence as well as other melodic transformations previously used by Massaro, Kallman, and Kelly with adults. In experiment 1, infants showed evidence of discriminating all transformations from the original melody. In Experiment 2, the task was made more difficult, and infants failed to discriminate transpositions of the original melody as well as transformations that preserved the melodic contour and approximate frequency range of the original melody. By contrast, infants showed evidence of discriminating transformations that violated the contour of the original melody or that included changes in the octaves from which component tones were drawn. This global processing strategy parallels that used by adults with atonal or unfamiliar tonal melodies.

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.

Infants 7 to II months of age were tested for their detection of a frequency relational change of one semitone in a five-note melody. Melodies were presented in various transpositions that altered absolute frequencies of the component tones but preserved the frequency ratios. In Experiment 1, two background melodies were based on major and minor triads, both of which occur commonly in Western tonal music. Contrast melodies were minor or major triads, respectively. Infants were able to discriminate these contrasting melodies that differed from the background melodies by one semitone. In Kxpcriment 2, infants were found to detect a semitone difference more easily when the major triad was background and a relatively uncommon triad, the augmented triad, was the contrast. They failed to make this discrimination when the roles of these two melodies as background and contrast were reversed. In a final study, infants discriminated the major and minor backgrounds used in Experiments 1 and 2 from contrasting variations, called inversions, that did not differ in triad quality as did previous background/contrast pairs. Therefore, encoding of triad quality alone cannot account for the evidence of discriminability in Experiments 1 and 2. Rather, the ability to detect a semitone difference in transposed melodies indicates that infants can respond to precise relations between the component tones of a melody based on familiar or stable structures. These findings also imply that sets of tones that arc unfamiliar or unstable may present encoding or memory difficulties for infants, as has been found for children and adults. RKSUMF. Dcs enfants agesde 7 a 11 mois ont etc cvalues sur leur capacity a detcctcr un changement de frequence rclationnellc d'un demi-ton dans une melodie de cinq notes. Les melodies eiaient presentees dans divcrses transpositions dc facon a altcrcr les frequences absolucs tout en prescrvant lcs rapports dc frequence. Dans Inexperience I, deux melodies de fond ctaient basees sur dcs triades majeures ct mineures, lcs deux ctant communement retrouvces dans la musiquc tonalc occidentalc. Lcs melodies dc contrastc ctaient dcs triades mineures ou majeures, respectivement. Lcs enfants ctaient capablcs dc discriminer les melodies contrastantcs qui difTeraicnt dcs melodies de fond d'un demi-ton. Dans ('experience 2, Ton rapportc que les enfants detcctaient plus facilemcnt une difference d'un demi-ton lorsque la triade majcure etait en fond ct qu 'une triade relativcment pcu commune, la triadc augmentcc, ctait la triade contrastee. Us etaient incapablcs de faire cctte discrimination lorsque les roles dc ces deux melodies ctaient inversees. Dans l'erudc finale, lcs enfants pouvaienf discrimincr le.s fonds majeurs ct mineurs utilises dans lcs experiences I ct 2 dcs variations contrastantcs, appclccs inversions, qui ne differaient pas dans la quality des triades tclles que I'ctaient lcs paires fond/contraste prccedentcs-*This research was supported by grants to Sandra E. Trehub from Ihe Natural Sciences and Engineering Rese...

We tested infants 6 to 8 months and children 5 Vi years of age for their discrimination of silent intervals between elements of auditory patterns. Standard patterns consisted of six 200-ms tones, three at 440 Hz and three at 659 Hz, with 200-ms intertone intervals (XXXOOO). Contrasting patterns differed only in the addition of a silent increment following the third tone (i.e., between tone groups, XXX OOO) or following the fourth tone (i.e., within a tone group, XXXO OO). Contrasting stimuli presented to infants had increments of 200, 125, 100, or 75 ms; those presented to children had increments of 100, 75, and 50 ms. Infants detected all increments in all locations except the 75ms increment in the between-group location, but there were no differences in performance for different increment locations. Children detected all increments, but performed significantly worse for between-group increments than for within-group increments. Thus, the context of a temporal increment influences its detectability for children, as it does for adults, indicating that children group the elements of auditory stimuli on the basis of frequency.

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 nondiatonic 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.

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 successfuly differentiated between three-tone 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.K£SUM£ NOUS avons presence a des enfants dc 7 a 9 mois des repetitions dc sequences de trois ou quatrc tons caracterisees par unc structure rythmique particuliere. Nous avons ensuite eValue leur capacitc a dctecter des changements dans la structure rythmique dc variations de tempo et de frequence presentees au hasard. Les enfants diffcrenciaient avec succes entrc des sequences de trois tons avec unc structure 1, 2 (X XX) et 2, I (XX X) ainsi que des sequences de quatre tons avec des structures 2, 2 (XX XX) et 3, 1 (XXX X). Dans d'autres laches, ils ont montrc leur habilete a discriminer cntrc des tempos contestants dans Ic contcxtc de variations de frequence. Nous concluons alors que les enfants peuvent categoriser des sequences auditives sur la base du rythme et aussi du tempo.

Extended previous research on perceptual grouping in infancy (Thorpe, Trehub, Morrongiello, & Bull, 1988). Infants' detection of temporal increments to silent intervals between groups of tones was compared with their detection of comparable silent increments within groups of tones. Ss were presented with standard 6-tone sequences, with the fust 3 tones differing from the last 3 in harmonic structure, frequency, or intensity, and contrasting sequences with increments of 80 or 100 ms to the silent interval between the 3rd and 4th tone (XXX OOO, between groups) or between the 4th and 5th tone (XXXO OO, within group). Infants discriminated temporally altered sequences from the standard only when the increments occurred within a group. The authors conclude that perceptual grouping processes are operative in infancy and that infants perceive the silent increments between groups of sounds as longer than identical intervals within a group, as do adults.