Abstract: Shimada

2. Nakamura M, Itoh N. (2008)　Hunting with tools by Mahale chimpanzees, Pan Africa News, 15, 2-6.

Many adults may have less subjective feelings of familiarity toward infants’ vocalizations since an infant’s sound are different from those of adults. However, mothers frequently exposed to infant’s vocalizations may be less averse to infants’ voices. To test this hypothesis, 21 mothers (M age = 31.1 ye., SD = 4.3) of infants (M age = 8.2 mo., SD = 3.5), 18 mothers (M age = 34.4 ye., SD = 4.8) of children between two and five years of age (M age = 2.8 ye., SD = 1.0), and 17 women (M age = 29.2 ye., SD = 11.1) with no children were exposed to 20 types of sounds. Of these sounds, 14 were produced by infants. Although the mothers of infants did not recognize sounds as those of an infant’s vocalization, they showed higher subjective feelings of familiarity toward the timbres of the vowel-like stimuli than did the other groups. By contrast, the subjective feelings of familiarity for nonspeech sounds did not differ among groups. Mateal experiences may change women’s recognition of perceived sounds.

1. Shimada Y., & Itakura, S. (2005). Alteation of adult’s auditory affinity to infant voice, Paper presented atSociety for Reproductive and Infant Psychology 25th annual conference,University of Amsterdam, Amsterdam, September 8-10.

Infants are thought to live in the perceptual world different from that of adults. This applies to auditory perception as well. Some precursory studies on linguistics and psychology show that infants produce various voices including the phonemes of foreign language that adults cannot distinguish. Such a voice is thought to be less affinitive for the ears of many adults who have already lost those phonemes. However, ears of mothers who frequently listen to their baby’s voice might be enhancing the range of affinity to infant vocal sound, which adult have lost, by their experience. We compared mothers with high exposure to baby’s voices and non-mothers with low exposure to baby’s voices in hearing impression tests. Participants listened to 19 units of sound, which consisted of 14 units of infant sound, 1 unit of an adult’s utterance as a baseline, and 4 units of animal voice as control stimuli and also as distracters. To exclude the influence of the context of the sound, the stimuli were cut in 1 second each. The stimuli were repeated 3 times and 1 second of white noise was inserted in between. After listening to each sound unit, they were asked to rate values related to affinity (e.g. noisiness, weirdness, whether it sounded like human voice). The score of affinity to vowel-like voice was significantly higher in the mother group than the non-mothers. This may be considered as a kind of aural alteation because they showed high affinity to timber of stimuli even when they did not know that that was a baby’s voice. This could be because in their daily life, mothers might hear infant voices with an expectation that the infants would produce language-like sounds. On the other hand, the score of not-vowel-like sounds was not different between the two groups. It may be because “not-vowel-like” sounds contained both kinds of sounds that are very different from and not very different from adults’ voices. These results suggest that experience as mothers alter their ears. Further investigation is needed to examine what kind of infant sound is affinitive to adult’s ears and what kind of other aural experience alter the range of affinity to infant voices.

2. Shimada, Y., & Itakura, S. (2006). Adults’ affinity for infant sound in accordance with Language experience, Paper presented atInteational Conference on Infant Studies, Kyoto, June 19-22.

Infant sounds are different from adults’, and their auditory sensitivity is also different. This thought to be because adults’ sounds and ears have already be converged into the sound of their native language although infants have not. Continuous experience of the language is also the sound experience, which may limit the range of sound they can use in their communication. If that is true, it may well be said that adults have different type of sound limitation in each type of input-language. Thus, we thought that people who have different language-sound experience show different degree of affinity with infant sounds. Methods: Japanese monolingual adults and Chinese (Mandarin and local Chinese languages) speaking adults and Dutch (Dutch, and also some European language after school age) listened to short sound stimuli including infant sounds. They rated their impression of affinity with each of the sound without any information about sound sources. The test stimuli were sampled from spontaneous sounds of a 5-month old infant, in the middle of the term of sound expansion according to Oller (1980). We distinguished vowel-like sounds from others because those sounds were thought to be more affinitive for adults who use similar sounds in their belonged language (Especially Chinese and Japanese in this study). To exclude the context of the sounds (an infant’s sounds), all the stimuli were cut down in 1 second each. We mixed some control stimuli picked up from a chimpanzee and a cat’s sound and Japanese adult’s speaking voice in the series of sounds. Participants listened to the stimuli three times each through a headphone and rated their degree of affinity; “Noisiness”, “Weirdness” (as negative degree) and “Likeness to human sound” (as positive degree) to each of the sounds on the 5-point scale rating sheet. Key Result: The rating score of affinity of control stimuli was not significantly different while that of vowel-like sound stimuli was significantly higher in Chinese-language group (p< .01 in negative questions, p< .05 in positive one). Also, Dutch-language group showed lower affinity with not-vowel-like infant sounds (only in negative questions, p< .01). Conclusion: The result suggested that the degree of affinity with infant sounds was different in accordance with language experiences. This will be argued as a matter of the relation between infant sounds and different, altered ears of adults which might affect adults' understandings to infants.

3.Shimada, Y., & Itakura, S. (2006). Adults’ affinity for infant sound in accordance with language experience, Paper presented atThe 4th Inteational Work Shop for Young Psychologist, Kyoto, September 2-3.

Adults’ different sound experience such as native language of each person or experience of particular sounds in their everyday life may result in different degree of sound tolerance or affinity. Especially with infant sounds, which include alien sounds for adults, adults may show the different degree of affinity according to their sound experience. We examined auditory affinity of (1) Japanese mothers and other Japanese women (2) Chinese and Dutch people with infant sounds in expansion period of sound development, which include wide range of sound quality. As each stimulus is cut down into 1 second, participants could not get any context of the sound flow. They listened to the test sounds without any information about sound sources. Result showed that Mothers compared to Non-mothers have higher degree of affinity to the sounds especially with vowel-like sounds. Also, Chinese were affinitive with the same kind of sounds as well, while Dutch were not so much. This result would be discussed in the context of difference or alteration of mateal auditory affinity.

4.Shimada, Y., & Itakura, S. (2006). Infant sound production as a playing behavior, Lancaster-Kyoto Joint Inteational Symposia, Lancaster, October 25-26.

Present study investigated the possibility that early infants’ sound production could be a playing behavior. Four to five month-old infants’ spontaneous sound was recorded in their home. To test our hypothesis that infants produce sound to hear the sound, we compared frequency and duration of the sound in each condition: 1. An adult respond naturally to the infant’s sound. 2. The infant was alone in the room and produce sound. 3. Infants was alone, hearing amplified feedback for their own sound. As a result, the frequency and duration of the sound were significantly higher in the condition 3 than the condition 2. The result suggested that the behavior was motivated by the sound feedback itself. The possibility that the sound production as a play is not related to communication with others but to the exploration of ecological self or to early motivation to art will be discussed.

5.Shimada, Y., Itakura, S. (2007), Infant sound production to listen to the sound; ontogenetic origin of singing, Paper presented at the 2007 Spring Meeting of the Japanese Society for Music Perception and Cognition, Hokkaido University, May 27.

Background: Infant sound in a social context has been shown to be an important factor in mother-infant interaction and in the development of infants, although few study investigated infant sound production without any responses from others. Some episodic studies have suggested that infants do produce sound in solitude as like they are “playing” alone. Cause there is no evidence that infants indeed show comfort sound when alone, pre research was needed. We asked mothers of young infants by questionnaire to report on this phenomenon. The result suggested that majority of mothers usually observe their infant produce “happy” sounds continuously in solitude. Previous studies suggested that infants show playful behavior in social situation or with an object. However, those studies did not considered infants’ playful behavior with sound produced by them selves. If the infants play with the sound, it might be related to an early motivation to joy of sound production. Purpose: The present study investigated the difference in sound pattes produced by infants when they are in interaction and in solitude. We hypothesized that infants produce sound in solitude, and the purpose of the behavior is sound feedback. Method: The experimenter visited each participant’s home to record the infant’s spontaneous behavior in solitude situation. A recorder (Roland Ediroll R-09, 24bit, 48khz) and two speakers (TIMEDOMEIN) were put on the bedside (or carpet side) in the room the infant was usually staying. Having set the apparatus, the experimenter went out to the next room or behind a partition where a video camera monitored the experiment. When the mother and the experimenter agreed that the infant was in comfort states, the mother started the first condition: 1) the respond condition, where the mother responded naturally to the infant. The other two conditions were started when the infant started to produce sound spontaneously and continuously in comfort states: 2) the no response condition, where the infant was alone in a comfortable state and produced sound spontaneously, and 3) the no response amplified condition, where the infant was alone and got amplified feedback of their own sound from two speakers. The frequency of sound production and total duration of sounds in the three conditions were compared. Results: The frequency of production of longer sound (more than one second) were significantly higher in the no-response condition than the respond condition, and in the no-response amplified condition than the no-response condition. The sound-to silence ratio was also increased in no-response condition and in no-response amplified condition. Actions defined as “Response-Waiting” (Tomasello, 1985) were observed often in the respond condition but less in the two solitude conditions. Conclusions: The result suggested that the infants’ behavior in solitude was promoted by the sound feedback itself as the amplified feedback condition provided them longer and louder echo increased the infants’ longer sounds. It is possible that the purpose of the behavior was not to wait for a response but a joy of sound; to use their vocal organs and/or listening to the sound feedback.

6.Shimada, Y., & Itakura, S. (2008). Infants’ sound production as a playing behavior, Paper presented at Inteational Conference on Human Behavior and Evolution Society, Kyoto University, July 4-8.

The present study hypothesized that infants produce sound in solitude for the purpose of listening to the sound feedback. When the infants were in comfort states, the mother started the test: 1) the respond condition, where the mother responded naturally to the infant. The other two conditions were started when the infant started to produce sound spontaneously: 2) the no response condition, where the infant was alone in a comfortable state and produced sound spontaneously, and 3) the no response ampli?ed condition, where the infant was alone and got ampli?ed feedback of their own sound from two speakers. The result showed infants continued to produced sound signi?cantly longer in the no-response condition than the respond condition, and in the no-response ampli?ed condition than the no-response condition. The result suggested that the infants’ behavior in solitude was promoted by the sound feedback itself.

7.Shimada, Y., & Itakura, S. (2008). Origin of singing; Infants’ vocalization in solitude, (Paper presented at) Inteational Conference on Music Psychology, Hokkaido university, August 25-29.

The present study reported here investigated the psychological meaning of infants’ vocalization when they are alone without any responses. In the experiment, we compared frequency and duration of the sound in three conditions; 1) an adult (caregiver) respond naturally to infant’s vocalization, 2) infants are kept alone and begin to vocalize spontaneously, 3) Infants are kept alone and begin to vocalize spontaneously, with amplified sound feedback by stereo speakers. In all conditions, infants did not express uncomfortable such as crying or fussing. As a result, the duration of the behavior was significantly higher in the amplified condition than the respond condition. Ratio of sound during the recording was marginally higher in the alone condition than the respond condition, and the alone with amplified feedback condition than alone condition. The results suggested that infants vocalize not only for response to others but also listening the sound of their own.