Characteristics of the rhythmic organization of vocal babbling: implications for an amodal linguistic rhythm

Vocal babbling involves production of rhythmic sequences of a mouth close–open alternation giving the perceptual impression of a sequence of consonant–vowel syllables. Petitto and co-workers have argued vocal babbling rhythm is the same as manual syllabic babbling rhythm, in that it has a frequency of 1 cycle per second. They also assert that adult speech and sign language display the same frequency. However, available evidence suggests that the vocal babbling frequency approximates 3 cycles per second. Both adult spoken language and sign language show higher frequencies than babbling in their respective modalities. No information is currently available on the basic rhythmic parameter of intercyclical variability in either modality. A study of reduplicative babbling by 4 infants and 4 adults producing reduplicated syllables confirms the 3 per second vocal babbling rate, as well as a faster rate in adults, and provides new information on intercyclical variability.     

Infant feeding and HIV in Sub-Saharan Africa: what lies beneath the dilemma?

The debate over how to best guide HIV-infected mothers in resource-poor settings on infant feeding is more than two decades old. Globally, breastfeeding is responsible for approximately 300,000 HIV infections per year, while at the same time, UNICEF estimates that not breastfeeding (formula feeding with contaminated water) is responsible for 1.5 million child deaths per year. The largest burden of these infections and deaths occur in Sub-Saharan Africa. Using this region as an example of the burden faced more generally in other resource-poor settings, we contrast the evolution of the clinical standard of care for infant feeding with HIV-infected mothers in high-income countries to the current international clinical guidelines for HIV-infected mothers and infant feeding in resource-poor settings. While the international guidelines of exclusive breastfeeding for a 6-month period seem to offer the least-worst strategy for reducing mother-to-child transmission of HIV during infancy while conferring some immunity through breastfeeding post-6 months, we argue that the impact of the policy on mothers and healthcare workers on the ground is not well understood. The harm reduction approach on the level of health policy translates into a complicated, painful moral dilemma for HIV-positive mothers and those offering them guidance on infant feeding. We argue that the underlying socio-economic disparities that continue to fuel the need for a harm reduction policy on infant feeding and the harm to women and children justify: (1) that higher priority be given to solving the infant feeding dilemma with improved data on safe feeding alternatives, and (2) support of innovative, community-driven solutions that address the particular economic and cultural challenges that continue to result in HIV-transmission to children within these communities.

Vowel categorization during word recognition in bilingual toddlers

Toddlers’ and preschoolers’ knowledge of the phonological forms of words was tested in Spanish-learning, Catalan-learning, and bilingual children. These populations are of particular interest because of differences in the Spanish and Catalan vowel systems: Catalan has two vowels in a phonetic region where Spanish has only one. The proximity of the Spanish vowel to the Catalan ones might pose special learning problems. Children were shown picture pairs; the target picture’s name was spoken correctly, or a vowel in the target word was altered. Altered vowels either contrasted with the usual vowel in Spanish and Catalan, or only in Catalan. Children’s looking to the target picture was used as a measure of word recognition. Monolinguals’ word recognition was hindered by within-language, but not non-native, vowel changes. Surprisingly, bilingual toddlers did not show sensitivity to changes in vowels contrastive only in Catalan. Among preschoolers, Catalan-dominant bilinguals but not Spanish-dominant bilinguals revealed mispronunciation sensitivity for the Catalan-only contrast. These studies reveal monolingual children’s robust knowledge of native-language vowel categories in words, and show that bilingual children whose two languages contain phonetically overlapping vowel categories may not treat those categories as separate in language comprehension.     

Causal perception of action-and-reaction sequences in 8- to 10-month-olds

Four experiments with 202 8- to 10-month-old infants studied their sensitivity to causation-at-a-distance in schematic events seen as goal-directed action and reaction by adults and whether this depends on attributes associated with animate agents. In Experiment 1, a red square moved toward a blue square without making contact; in “reaction” events blue moved away while red was approaching, whereas in “delay” events blue started after red stopped. Infants were habituated to one event and then tested on its reversal. Spatiotemporal features reversed for both events, but causal roles changed only in reversed reactions. Infants dishabituated more to reversed reaction events than to reversed delay events. Squares moved rigidly or in a nonrigid animal-like fashion. Infants discriminated these, but motion pattern did not affect responses to reversal. Infants also discriminated reactions from launching and dishabituated to reversed reactions lacking self-initiated motion. These results suggest that sensitivity to causation-at-a-distance depends on the event structure but not pattern or onset typical of animal motion.     

Infants’ auditory enumeration: Evidence for analog magnitudes in the small number range

Vigorous debate surrounds the issue of whether infants use different representational mechanisms to discriminate small and large numbers. We report evidence for ratio-dependent performance in infants’ discrimination of small numbers of auditory events, suggesting that infants can use analog magnitudes to represent small values, at least in the auditory domain. Seven-month-old infants in the present study reliably discriminated two from four tones (a 1:2 ratio) in Experiment 1, when melodic and continuous temporal properties of the sequences were controlled, but failed to discriminate two from three tones (a 2:3 ratio) under the same conditions in Experiment 2. A third experiment ruled out the possibility that infants in Experiment 1 were responding to greater melodic variety in the four-tone sequences. The discrimination function obtained here is the same as that found for infants’ discrimination of large numbers of visual and auditory items at a similar age, as well as for that obtained for similar-aged infants’ duration discriminations, and thus adds to a growing body of evidence suggesting that human infants may share with adults and nonhuman animals a mechanism for representing quantities as “noisy” mental magnitudes.     

Statistical inference and sensitivity to sampling in 11-month-old infants

Research on initial conceptual knowledge and research on early statistical learning mechanisms have been, for the most part, two separate enterprises. We report a study with 11-month-old infants investigating whether they are sensitive to sampling conditions and whether they can integrate intentional information in a statistical inference task. Previous studies found that infants were able to make inferences from samples to populations, and vice versa [Xu, F., & Garcia, V. (2008). Intuitive statistics by 8-month-old infants. Proceedings of the National Academy of Sciences of the United States of America, 105, 5012-5015]. We found that when employing this statistical inference mechanism, infants are sensitive to whether a sample was randomly drawn from a population or not, and they take into account intentional information (e.g., explicitly expressed preference, visual access) when computing the relationship between samples and populations. Our results suggest that domain-specific knowledge is integrated with statistical inference mechanisms early in development.     

Thought translation, tennis and Turing tests in the vegetative state

Brain damage can cause massive changes in consciousness levels. From a clinical and ethical point of view it is desirable to assess the level of residual consciousness in unresponsive patients. However, no direct measure of consciousness exists, so we run into the philosophical problem of other minds. Neurologists often make implicit use of a Turing test-like procedure in an attempt to gain access to damaged minds, by monitoring and interpreting neurobehavioral responses. New brain imaging techniques are now being developed that permit communication with unresponsive patients, using their brain signals as carriers of messages relating to their mental states.     

Yawning frequency and distribution in preterm and near term infants assessed throughout 24-h recordings

Yawning has been observed in foetuses and preterm infants. The aim of this study was to assess the frequency and the 24 h distribution of yawning in preterm infants.Twelve low-risk infants between 31 and 40 weeks of post-conceptional age (PCA) were continuously video-recorded for 24 h in their incubator. Spontaneous yawning was defined as opening of the mouth to its full extension in a dramatic stretch movement.The results showed that the rate of yawning across the 24-h period was 1.10/h. The highest incidence of yawns was in the waking motility pattern when compared to active sleep or quiet sleep motility patterns.Between 31 and 40 weeks, yawn incidence significantly decreased mainly during the day. The marked decrease in yawn frequency with age may be related to the development of circadian and homeostatic control of sleep and wake.     

Risk and Protective Factors for Children of Adolescents: Maternal Depression and Parental Sense of Competence

We investigated the relationship between depression and parental sense of competence to child cognitive outcomes for a sample of 49 adolescent mothers and their young children (Mean age=9 1/2 months) enrolled in a student parenting program. Cognitive development of the infants and toddlers was assessed using the Bayley Scales of Infant Development. Maternal depression was assessed with the CES-D and parental competence measured with the Parental Sense of Competence Scale. Results indicated that maternal depression and parental sense of competence alone did not predict children’s cognitive scores; the interaction of the variables significantly predicted children’s outcomes. Mothers reporting high levels of depression, who self-reported high levels of parental competence, had children who scored higher on the Bayley. Children of mothers with high levels of depression, and low reported levels of competence scored lower on the Bayley. The relationship was not significant for mothers reporting low levels of depression. Our findings suggest additional research needs to focus on the buffering effect of parental sense of competence for adolescent mothers experiencing depression.