Premenstrual enhancement of snake detection in visual search in healthy women.

It is well known that adult humans detect images of snakes as targets more quickly than images of flowers as targets whether the images are in color or gray-scale. When such visual searches were performed by a total of 60 adult premenopausal healthy women in the present study to examine whether their performance would fluctuate across the phases of the menstrual cycle, snake detection was found to become temporarily enhanced during the luteal phase as compared to early or late follicular phases. This is the first demonstration of the existence of within-individual variation of the activity of the fear module, as a predictable change in cognitive strength, which appears likely to be due to the hormonal changes that occur in the menstrual cycle of healthy women.

The influence of color on snake detection in visual search in human children.

It is well known that adult humans detect snakes as targets more quickly than flowers as the targets and that how rapidly they detect a snake picture does not differ whether the images are in color or gray-scale, whereas they find a flower picture more rapidly when the images are in color than when the images are gray-scale. In the present study, a total of 111 children were presented with 3-by-3 matrices of images of snakes and flowers in either color or gray-scale displays. Unlike the adults reported on previously, the present participants responded to the target faster when it was in color than when it was gray-scale, whether the target was a snake or a flower, regardless of their age. When detecting snakes, human children appear to selectively attend to their color, which would contribute to the detection being more rapidly at the expense of its precision.

Preference for infant-directed singing in 2-day-old hearing infants of deaf parents.

L. J. Trainor (1996) reported preferences for infant-directed versus infant-absent singing in English in 4-7-month-old hearing infants of English-speaking hearing parents. In this experiment, the author tested preferences for infant-directed singing versus adult-directed singing in 15 two-day-old hearing infants of deaf parents for a Japanese and an English play song. Using a modified visual-fixation-based auditory-preference procedure, the author found that infants looked longer at a visual stimulus when looking produced infant-directed singing as opposed to adult-directed singing. These results suggest that infants prefer infant-directed singing over adult-directed singing and that the preference is present from birth and is not dependent on any specific prenatal or postnatal experience.

[Synchronization between preverbal vocal behavior and motor action in early infancy. II: An acoustical examination of the functional significance of the synchronization].

Normal infants start to produce canonical babbling (CB) at the age of 6 to 10 months. CB consists of reduplicated sequences of consonant-vowel syllables which have adult-like acoustical features. Therefore, onset of CB is considered to be a landmark in the development of spoken language. The previous study indicated that a behavioral synchronization of vocalizations with rhythmic actions occurred in infants before the onset of CB. The present study examined the function of synchronization. Acoustical analyses were conducted on vocalizations of four infants during three-months-period including the month when synchronization occurred most frequently. The results show that both utterance length and formant frequency transition duration of synchronized vocalizations are shorter than those of non-synchronized vocalizations. These acoustical features, which are required to produce CB, persisted even after the synchronization has disappeared. The present study suggests that synchronization of vocalizations with rhythmic actions has the function of prompting infants to produce CB.

Perception of motherese in Japanese sign language by 6-month-old hearing infants.

N. Masataka (1996) reported results of an experiment in which 6-month-old deaf infants were presented with videotapes that showed 5 identical scripts signed in Japanese Sign Language by 5 deaf mothers toward their deaf infants or toward their deaf friends. The experiment demonstrated that infants showed greater attentional and affective responsiveness to infant-directed signing than to adult-directed signing. The present study explored the possibility that this same phenomenon might extend to hearing infants who have never been exposed to signed language. When the same stimulus tape as used previously was presented to 45 six-month-old hearing infants, they too showed greater attentional and affective responsiveness to infant-directed sign than to adult-directed sign. This fact suggests that infants are prepared to detect sign motherese characteristics without specific experience in the modality.

[Xenotransplantation].

A Bulk of studies on xenotransplantation have been accumulated for the last few years. Most of the studies focus in the investigation for etiologic mechanism of hyperacute rejection seen in the xenotransplantation between distant species. Underlying pathophysiology in hyperacute rejection is primarily based on initial antigen-antibody reaction between oligosaccharide epitope of the xenogeneic organ and natural antibody in the recipient plasma. Subsequent activation of complement cascade and activation of the endothelial cell constitute an integral part of the entire complexity of the hyperacute rejection. We herein summarize the updated knowledge and provide an overview on this interesting research field.

[On the function of swaddling as traditional infant-care practiced by Native South Americans].

Placing the infant in a device which restrained his/her movement was a traditional custom of infant caretaking in a number of parts of the world, and is still observed in some of them. An example of such practices, swaddling, was investigated with Native Americans, the Aymara, in Bolivia, and caretaking behaviors in 24 swaddling and 18 non-swaddling families were compared. Results did not support the notion that swaddling was a form of infant neglect on the part of caretakers. Swaddling caretakers actually exhibited as strong interest in the infant as non-swaddling caretakers, and spent more money on his/her clothes. The mother spent less time for infant care in the swaddling family. However, other members of the family took more time to take care of the infant than those in the non-swaddling family. It is argued that swaddling effectively encourages non-mother family members to participate in infant caretaking, in addition to serving a potentially beneficial function to protect infants from unsafe and unsanitary home environments.

The relation between index-finger extension and the acoustic quality of cooing in three-month-old infants.

Fourteen full-term, healthy, three-month-old infants were observed during a total of 15 minutes spontaneous face-to-face interaction with their mothers. Facial and manual actions, gaze direction and vocalizations were coded. The infants' cooing vocalizations were categorized into syllabic and vocalic sounds. Index-finger extension occurred frequently in sequence with syllabic sounds, which are speech-like vocalizations, but rarely occurred in sequence with vocalic sounds. No other categories of nonvocal behaviours showed such a relationship. In a subsequent experiment, the infants experienced either conversational turn-taking or random responsiveness from their mothers. In the turn-taking condition, the infants produced a higher ratio of syllabic to vocalic sounds, and a higher frequency of index-finger extension. These results suggest a strong connection between speech and the pointing gesture long before the infant can actually talk.

Effects of contingent and noncontingent maternal stimulation on the vocal behaviour of three- to four-month-old Japanese infants.

A total of 48 male infants experienced either conversational turn-taking or random responsiveness of their mothers when aged 0;3 and 0;4. In both periods, the infant's rate of vocalizing was not significantly influenced by the contingency of the mother's response, but contingency altered the temporal parameters of the infant's vocal pattern. Infants tended to produce more bursts or packets of vocalizations when the mother talked to the infant in a random pattern. When the infants were aged 0;3 such bursts occurred most often at intervals of 0.5-1.5 sec whereas when they were aged 0;4 they took place most frequently at significantly longer intervals, of 1.0-2.0. The difference corresponded to the difference between intervals with which the mother responded contingently to vocalizations of the infant at 0;3 and at 0;4. While the intervals (between the onset of the infant's vocalization and the onset of the mother's vocalization) rarely exceeded 0.5 sec when the infant was aged 0;3, they were mostly distributed between 0.5 and 1.0 sec when he was aged 0;4. After vocalizing spontaneously, the infant tended to pause as if to listen for a possible vocal response from the mother. In the absence of a response, he vocalized repeatedly. The intervals between the two consecutive vocalizations were changed flexibly by the infant according to his recent experience of turn-taking with the mother.

Early ontogeny of vocal behavior of Japanese infants in response to maternal speech.

Discriminant analysis was used to distinguish statistically between the comfort-state vocalizations uttered by Japanese infants following 5 different types of pitch contours of maternal speech. Ontogenetic changes of their vocal behaviors were investigated during the first 5 months of life. Structural variability in infant vocalizations across variants of maternal speech was found to be characterized by a set of quantifiable physical parameters. However, infant's age when a vocalization was recorded was not an important contributor. Successful attempts at cross-validation, in which the discriminant profiles derived from one sample of vocalizations were used to classify a second set of vocalizations, indicated that the result obtained was not an artifact of using the same data set to derive the profiles to test reclassification accuracy. Proportion of cross-validated vocalizations that were misclassified decreased as age increased. The results of the present study demonstrate that a statistically significant relation exists between acoustic features of maternal speech and those of following infant vocalizations, and that such a relation strengthens over age.

Pitch characteristics of Japanese maternal speech to infants.

The fundamental frequency F0 patterns of maternal-speech addressed to infants aged 0;3-0;4 were measured quantitatively. Speech samples were recorded when six Japanese-speaking mothers addressed an adult and their own infants. Japanese mothers speaking to adults use a relatively restricted F0 range, concentrated around the mother's F0, which tends to be near the low end of the total range used. These acoustic characteristics are not altered substantially when these same women speak to their infants in initial utterances to attract the infants' attention. If such attempts are unsuccessful, however, they are likely to make more exaggerated utterances, in which F0 shifts upward and the frequency range is significantly increased. Moreover, only when acoustic characteristics of maternal speech to infants are exaggerated, can the type of F0 contour of the infant's subsequent response be predicted to a significant extent from the mother's preceding utterance.

Primate play vocalizations and their functional significance.

It is well known that, among mammals, specific play vocalizations are produced exclusively by certain nonhuman primate species. In order to investigate the functional significance of these calls, we examined their phyletic distribution among New World and Old World monkeys. The results indicate that such calls are produced by species in which allomothering behaviour occurs. We propose a functional explanation of play vocalizations according to which they serve as a possible source of information for maternal retrieval of infants whenever necessary.

Development of vocal recognition of mothers in infant Japanese macaques.

Individual vocal recognition was studied in infant Japanese macaques by presenting natural calls of mothers and nonmother cagemates to them in a habituation-dishabituation paradigm. Discriminability was measured by an increase in conditioned sucking response rate to a second stimulus call after habituation to the first stimulus call. Recovery from habituation was greater in subjects over 190 days postconception when mother's vocalizations were played back after the stimulus change than when sounds of others were presented. Results demonstrate that the subjects could sort acoustic variants of vocalizations given by their cagemates into at least two categories (mother versus others) and suggest that vocal recognition of mothers develops relative to postconception (maturational) rather than postnatal age in Japanese macaques.