The effects of SES on infant and maternal diurnal salivary cortisol output

The present study directly compared diurnal salivary cortisol output and maternal-infant synchrony in low and high socio-economic status (SES) mother–infant dyads. Saliva cortisol samples were collected from 32 6–12-month-old infants and their mothers on the same day in the morning, afternoon and evening, and assayed for free cortisol concentration. Low-SES infants and mothers exhibited higher average salivary cortisol output, without dysregulation, compared to high-SES infants. Low-SES infants and mothers also showed reduced synchrony in cortisol output compared to high-SES infants and mothers. Results are discussed with respect to maternal sensitivity and early stress reduction interventions.     

Socio‐economic Status (SES) Affects Infants' Selective Exploration

Infants change their behaviours in accordance with the objects they are exploring. They also tailor their exploratory actions to the physical context. This selectivity of exploratory actions represents a foundational cognitive skill that underlies higher‐level cognitive processes. The present study compared the development of selective exploratory behaviours in high and low socio‐economic status (SES) infants. Sixty‐one 6–8‐ and 10–12‐month‐old infants were presented with rigid and flexible cubes on a tray that was half rigid and half flexible. There were SES effects for each category of exploratory behaviours: object only, surface only and object–surface interactions. Low‐SES infants engaged in comparable amounts of exploratory behaviours with high‐SES infants, but they exhibited behaviours less conducive to information uptake, compared with high‐SES infants. The results suggest difficulty for low‐SES infants in transitioning to more mature exploration strategies. Copyright © 2015 John Wiley & Sons, Ltd.     

Learning to walk changes infants’ social interactions

The onset of crawling marks a motor, cognitive and social milestone. The present study investigated whether independent walking marks a second milestone for social behaviors. In Experiment 1, the social and exploratory behaviors of crawling infants were observed while crawling and in a baby-walker, resulting in no differences based on posture. In Experiment 2, the social behaviors of independently walking infants were compared to age-matched crawling infants in a baby-walker. Independently walking infants spent significantly more time interacting with the toys and with their mothers, and also made more vocalizations and more directed gestures compared to infants in the walker. Experiment 3 tracked infants’ social behaviors longitudinally across the transition from crawling and walking. Even when controlled for age, the transition to independent walking marked increased interaction time with mothers, as well as more sophisticated interactions, including directing mothers’ attention to particular objects. The results suggest a developmental progression linking social interactions with milestones in locomotor development.     

Number Versus Contour Length in Infants' Discrimination of Small Visual Sets

This study examined infants' use of contour length in number discrimination tasks. We systematically varied number and contour length in a visual habituation experiment in order to separate these two variables. Sixteen 6- to 8-month-old infants were habituated to displays of either two or three black squares on a page. They were then tested with alternating displays of either a familiar number of squares with a novel contour length or a novel number of squares with a familiar contour length. Infants dishabituated to the display that changed in contour length, but not to the display that changed in number. We conclude that infants base their discriminations on contour length or some other continuous variable that correlates with it, rather than on number.     

Attentional Predictors of 5‐month‐olds' Performance on a Looking A‐not‐B Task

In the first year of life, the ability to search for hidden objects is an indicator of object permanence and, when multiple locations are involved, executive function (i.e. inhibition, cognitive flexibility and working memory). The current study was designed to examine attentional predictors of search in 5‐month‐old infants (as measured by the looking A‐not‐B task), and whether levels of maternal education moderated the effect of the predictors. Specifically, in a separate task, the infants were shown a unique puppet, and we measured the percentage of time attending to the puppet, as well as the length of the longest look (i.e., peak fixation) directed towards the puppet. Across the entire sample (N = 390), the percentage of time attending to the puppet was positively related to performance on the visual A‐not‐B task. However, for infants whose mothers had not completed college, having a shorter peak looking time (after controlling for percentage of time) was also a predictor of visual A‐not‐B performance. The role of attention, peak fixation and maternal education in visual search is discussed. Copyright © 2015 John Wiley & Sons, Ltd.     

The role of crawling and walking experience in infant spatial memory

This research explored infants' use of place learning and cue learning in a locomotor task across the transition from crawling to walking. Novice and expert crawling and walking infants were observed in a novel locomotor task-finding a hidden goal location in a large space. In Experiment 1, infants were tested with distal landmarks. Infants with fewer than 6 weeks of experience, either crawling or walking, could not find the goal location. All infants with more locomotor experience were more successful. Learning did not transfer across the transition to walking. In Experiment 2, novice and expert crawlers and walkers were tested with a direct landmark. Again, novice crawlers and walkers with fewer than 6 weeks of experience could not find the goal, whereas those with more experience could. Taken together, these findings suggest that infants' spatial learning is inextricably linked to mode of locomotion.