Eve E. Perris

Object Representation Guides Infants' Reaching in the Dark

Infants were presented with two sounding objects of different sizes in light and dark, in which sound cued the objects identity. Reaching behavior was assessed to determine if object size influenced preparation for grasping the object. In both light and dark, infants aligned their hands when contacting the large object compared with the small object, which resulted in a reach with both hands extended for the large object and reach with one hand more extended for the small object. Infants contacted the large object more frequently on the bottom and sides rather than the top, where the sound source was located. Reaching in the dark by 6 1/2-month-olds is not merely directed toward a sound source but rather shows preparation in relation to the objects size. These findings were interpreted as evidence that mental representation of previously seen objects can guide subsequent motor action by 6 1/2-month-old infants.

Infant timbre perception: Discrimination of spectral envelopes

Seven-month-old infants were trained to discriminate the timbre of tonal complexes that differed in their spectral envelopes. In a conditioned head-turning paradigm, infants initially learned to discriminate stimuli that had the same fundamental frequency, 200 Hz, but different harmonic components (Le., frequencies). After successfully completing the basic timbre discrimination, the same infants learned to discriminate less salient stimuli from which the fundamental frequency had been removed. These results suggest that young infants can analyze the spectra of tonal complexes and discriminate differences in one of the most important cues for timbre perception in adults, the spectral envelope.

Fifty months of memory: A longitudinal study in early childhood.

Three studies were conducted to evaluate long-term memory longitudinally. In Study 1, 10-month-olds (N = 20) were taught to operate a toy in their homes and were tested at home after four months, as were age-matched (14 months) inexperienced controls (N = 20). Experienced infants were more willing to remain in the play situation, relearned faster than controls, and one operated the toy spontaneously. In Study 2, conducted 18 months thereafter, two subgroups (N = 5) of Study 1 groups and an age-matched (32 months) control group (N = 5) were observed in a lab playroom. Only the children with experiences at both 10 months and 14 months operated the toys without being shown. Children with a single 14-month experience made equivalent numbers of toy contacts and successful responses, however, and both groups exceeded controls. In Study 3, conducted 2+ years after Study 2, 36 children played in a novel playroom. Subgroups differed in amount and timing of experience (in Studies 1 and 2); a naive age-matched (60 months) control group (N = 6) was added. Controls took longer to make the toy work than children in the combined experience groups. Only experienced children elected to operate the toys later in the session. Two children verbally recalled part of the 10-month event. The findings are discussed in the light of their relevance to the assessment and description of memory during early childhood.

Does reaching in the dark for unseen objects reflect representation in infants

Five groups of 7-month-old infants had varying amounts of experience with a sounding object in the light before being presented with it in the dark. Neither visual nor auditory experience was necessary for accurate reaching in the dark, suggesting that infants represented the unseen object.

Timbre discrimination by 7‐month‐old infants

While previous research has demonstrated the infants ability to categorize sounds according to their pitch in the presence of irrelevant spectral variations, little or no research has evaluated discrimination of those spectral variations. In the present study, 7‐ to 8‐month‐old infants demonstrated the ability to discriminate harmonic tonal complexes from two timbre categories that differed in their spectral energy distributions. These differences in timbre were identical to the irrelevant variations over which infants categorized sounds in earlier work. In a conditioned head‐turning paradigm, infants initially learned to discriminate stimulus tokens that contained the same fundamental frequency, 200 Hz, but different harmonic components (e.g., harmonics 5–10 versus harmonics 3–8 or 7–12). After successfully completing the basic timbre discrimination, the same infants transferred their learning to missing fundamental stimuli that had novel spectral energy distributions (e.g., harmonics 4–9 versus harmoni...