Exploration of vocal tract properties during serial production of vowels by full term and preterm infants

This study examines the acoustic characteristics of individual vowels and those produced in sequences of three or more during vocal play by full term and preterm at age 6 months. Laboratory and home audiotape recordings of infant vowel sounds were made and digitized for acoustic analysis. Of interest was whether, during production of vowel sequences compared to those produced singly, infants explored the relation between tongue height and tongue advancement, as measured acoustically by the first formant (F1) and second formant (F2) frequencies, respectively. In both groups of infants, the region of F1-F2 space for individually produced vowels was significantly greater than for vowels produced in sequence. High correlation coefficients for F1 and F2 during exploration of vowels produced in sequence were apparent in full term, but not preterm infants. The data support the claim that vowels produced in sequence occupy a more limited region of the vocal tract than those produced singly, and that infants explore the characteristics of their vocalizations within sequences.     

Development of a view-invariant representation of the human head

Do infants perceive visual cues as diverse as frontal-view faces, profiles or bodies as being different aspects of the same object, a fellow human? If that is the case, visual exposure to one such cue should facilitate the subsequent processing of the others. To verify this hypothesis, we recorded event-related responses in 4-month-old infants and in adults. Pictures of eyes were interleaved amongst images belonging to three human contexts (frontal-view faces, profiles or bodies) or non-human contexts (houses, cars or pliers). In adults, both profile and frontal-face contexts elicited suppression of the N170 response to eye pictures, indicating an access to a view-invariant representation of faces. In infants, a response suppression of the N290 component was recorded only in the context of frontal faces, while profile context induces a different effect (i.e., a P400 enhancement) on eye processing. This dissociation suggests that the view-invariant representation of faces is learned, as it is for other 3-D objects and needs more than 4 months of exposure to be established. In a follow-up study, where infants were exposed to a short movie showing people rotating their heads, the profile-induced P400 effect was speeded up, indicating that exposure to successive views of the same object is probably a way to build up adult-like face representations.     

Hold your horses: how exposure to different items influences infant categorization

We investigated how exposure to pairs of different items (as compared with pairs of identical items) influences 10-month-olds' (n=79) categorization of horses versus dogs in an object-examining task. Infants responded to an exclusive category when familiarized with pairs of different items but not when familiarized with pairs of identical items (Experiment 1), even when the frequency of exposure to each item was controlled (Experiment 2). When familiarized with pairs of identical items, infants failed to show evidence of memory for the individual exemplars (Experiment 3). Reducing the retention interval between presentations of different items in the identical pairs condition facilitated infants' recognition of an exclusive categorical distinction (Experiment 4). These results are discussed in terms of how exposure to collections of different items, and how opportunities to compare items, influences infants' categorization.     

Carrying human infants – An evolutionary heritage

We propose that infant carrying is a biological norm for human caregiving, given that human infants have evolved a capacity to cling onto an upright caregiver whose body co-evolved to enable offspring carrying. The origins of this mutual adaptation may date back 4 million years, with the emergence of bipedalism, which precluded the infant horizontal and gravity-supported position on the back of a quadrupedal caregiver. We describe infant cooperative reflexes and behaviors, including the carrying-induced calming response and discuss hypotheses for the invention of infant carrier tools.Carrying involves several physiological and behavioral parent-infant co-adaptations that imply it is an evolutionarily conserved strategy. Epigenetic transmission of reproductive behavior through generations affects the development of the offspring, as well as the mental health of the parent. Carrying might have contributed to the evolution of Hominidae, potentially aiding dexterity, handedness, language acquisition, and social interactions.We review the evolutionary milestones and time points where the infant-caregiver interactions might have changed, exploring infant carrying as it intersects with biological and cultural evolution. We briefly summarize the effects of infant carrying on physiological, epigenetic, and socio-emotional outcomes.     

Rhyming abilities in 9-month-olds: The role of the vowel and coda explored

Nine-month-olds can respond to a change in rhyme when the conditioned head turn procedure is used [Hayes, R. A., Slater, A., & Brown, E. (2000). Infants’ ability to categorise on the basis of rhyme.Cognitive Development, 15, 405–419]. However, it is not known whether infants are detecting the change in vowel, the change in coda, or both. In Study 1, it was found that 9-month-old infants clearly attend to both the vowel and coda of the syllables presented, since they successfully categorised the syllables on the basis of both. However, infants found it harder to detect the difference when only the vowel or the coda changed than when both changed, a pattern of results that was also found in Study 2 with adults. These findings suggest that preverbal 9-month-olds parse syllables into smaller units than just onset and rime, and do so in a manner that is comparable to that of adults. The findings are discussed in relation to work demonstrating a relationship between rhyming ability and competence in word learning, reading and writing.     

Effect of external motion on correspondence between infant actigraphy and maternal diary

Correspondence between infant actigraphy and mother-recorded diary differed significantly when receiver–operator function area under the curve, correlation, and logistic regression was calculated with and without excluding periods of external motion. External motion occurred in 40% of recording time and significantly changed activity count per epoch.     

The Problem of Other Minds

This paper reimagines the traditional problem of other minds. On a Cartesian view, the problem involves humans’ inability to perceive other persons’ minds. Similarly, Gilbert Ryle claims that we cannot directly access another’s mind. The paper’s rethinking of the problem of other minds moves beyond these questions of perceptibility and accessibility. It asks whether there are certain groups of people whose minds are systematically misinterpreted, or even denied mentality. It argues that there are. This claim builds off recent work in philosophy and social psychology on epistemic injustice and the role of social categories in mental state attribution. The paper proposes the Problem of the Other’s Mind: the phenomenon of a (relatively) socially privileged person’s inability or lack of desire to understand the mind of a (relatively) socially underprivileged person.     

Infant sleep moderates the effect of infant temperament on maternal depressive symptoms,maternal sensitivity,and family functioning

Observed infant temperamental difficulty and infant sleep efficiency and sleep variability were examined as predictors of maternal depressive symptoms, maternal sensitivity, and family functioning. Eight observations at 8-months postpartum were used to assess infant temperament, and actigraphy was used to measure infant sleep for 1-week at the time of the 8-month assessment. Structured clinical interviews were used to assess maternal depressive symptoms between 5 and 12 months postpartum and at 15 months postpartum, and observational assessments were used to assess maternal sensitivity and family functioning at 15 months postpartum. Variability in infant sleep moderated the effect of infant temperament on maternal depressive symptoms, maternal sensitivity, and family functioning. Infant temperament was positively associated with maternal depressive symptoms when variability in infant sleep efficiency was high, but not when variability in infant sleep efficiency was low. Likewise, infant temperament was negatively associated with maternal sensitivity and family functioning when variability in infant sleep efficiency was high, but not when variability in infant sleep efficiency was low. Results underscore the importance of infant sleep for maternal and family health.     

Concurrent anticipation of two object dimensions during grasping in 10-month-old infants: A quantitative analysis

The anticipation of more than one object dimension while grasping for objects has been rarely investigated in infancy. The few existing studies by Newell et al. and Schum et al. have revealed mixed results probably mainly due to methodological limitations. Therefore, the present experiments tested concurrent anticipatory grasping for two object dimensions, namely, object size and object orientation using a quantitative motion capture system (Vicon), in 10-month-old infants and adults. We presented objects varying in size (small vs. large) and orientation (horizontally vs. vertically) and analyzed participants’ anticipatory hand configurations. As with adults, we observed that infants rotated their wrists, thumbs, and index fingers as a function of object orientation and adjusted their maximum grip apertures and their grip apertures shortly before they touched the objects as a function of object size. Analyses on an individual level showed that infants like adults anticipated both dimensions when the maximal values of aperture and angle were used but not when the measures shortly before touch were considered. Thus, the ability to anticipate more than one object dimension can already be observed at 10 months of age but seems to improve considerably over the first year of life.     

Is sensory processing an issue for infants with colic?

ObjectivesTo determine the association between sensory functioning, sleep, cry/fuss, and feeding behaviors of infants with colic younger than 4 months of age.MethodsDunn’s Infant/Toddler Sensory Profile™ and a modified Barr Baby Day Diary^© were used to assess 44 breastfed infants with colic under four months of age. Colic was defined according to Wessel’s criteria.ResultsThirty-four of the 44 infants with colic (77%) scored as atypical for sensory processing. Of these, 56% scored atypical for sensory processing on quadrant one (Q1) (Low Registration), with 24%, 65%, and 18% scoring as atypical for sensory processing on Q2 (Sensory seeking), Q3 (Sensory sensitivity), and Q4 (Sensation avoiding), respectively. All infants demonstrating sensation avoiding also scored as Low Threshold. A moderate statistically significant correlation was found between sensation seeking and time spent sleeping (r = 0.31; p = 0.04). No other statistically significant associations between infant behaviors and their sensory functioning were demonstrated. Overall, infants demonstrating atypical sensory responses (in any quadrant) slept significantly more than infants demonstrating typical sensory responses (mean difference = −67.8 min/day; 95% CI = −133.6 to −2.1; p = 0.04).ConclusionVery limited associations between infant behaviors and sensory functioning were demonstrated, suggesting that sensory functioning may not be a significant factor in the multifactorial nature of infant colic. Further well-designed studies using validated tools for infants with colic are required to determine whether associations between infant behaviors and sensory functioning exist.