Browsing by Subject "Cognitive development"

The uniquely human mathematical mind sets us apart from all other animals. Although humans typically think about number symbolically, we also possess nonverbal representations of quantity that are present at birth and shared with many other animal species. These primitive numerical representations are thought to arise from an evolutionarily ancient system termed the Approximate Number System (ANS). The present dissertation aims to determine how these preverbal representations of quantity may serve as the foundation for more complex quantitative reasoning abilities. To this end, the five studies contained herein investigate the relations between representations of number, representations of other magnitude dimensions, and symbolic math proficiency in infants, children, and adults. The first empirical study, described in Chapter 2, investigated whether infants engage the ANS to represent the full range of natural numbers. The study presented in Chapter 3 compared infants' acuity for detecting changes in contour length to their acuity for detecting changes in number to assess whether representations of continuous quantities are primary to representations of number in infancy. The study presented in Chapter 4 compared individual differences in acuity for number, line length, and brightness in children and adults to determine how the relations between these magnitudes may change over development. Chapter 5 contains a longitudinal study investigating the relation between preverbal number sense in infancy and symbolic math abilities in preschool-aged children. Finally, the study presented in Chapter 6 investigated the mechanisms underlying the maturation of the number sense and determined which features of the number sense are predictive of symbolic math skill. Taken together, these findings confirm that number is a salient feature of the environment for infants and young children and suggest that approximate number representations are fundamental for the acquisition of symbolic math.

Many diverse adult diseases, from diabetes to dementia, are increasingly viewed as arising, in part, from early life environmental influences. The so-called Developmental Origins of Health and Disease (DOHaD) research paradigm offers the potential to improve our understanding of the etiology of many hard-to-treat adult diseases by focusing researcher’s attention on the pre and post-natal and early childhood years, where small interventions could pay large dividends later on. Along with great potential, the DOHaD framework offers great challenges, as it is logistically and conceptually difficult to investigate the environmental origins of chronic diseases that may manifest only decades after harmful exposures. This dissertation presents a series of five original studies that sought to answer open empirical questions about the developmental origins of health and disease focusing on early-life factors that influence the health and aging of the brain. Three increasingly broad "levels" of the early life environment are considered across three sequential dissertation chapters: (1) the individual micro-physical level, (2) the family level, and (3) the neighborhood level. At each level this dissertation considers at least one exposure that has relevance to researchers and policy makers, either because, like exposure to neighborhood vegetation / greenery, it may offer a good route for intervention (e.g., the exposure is potentially modifiable) or because, like exposure to the heavy metal lead, it is understood to be more widespread than previously assumed. Studies were conducted using data from two population-representative longitudinal birth cohorts, the New Zealand-based Dunedin Multidisciplinary Health and Development Study (born in 1972-1973) and the United Kingdom-based Environmental Risk Longitudinal Twin Study (born in 1994-1995). Across the five studies, results supported the DOHaD framework and provided new evidence about the long-term consequences of childhood exposure to lead, adversity (e.g., physical and emotional abuse, household dysfunction, etc.), and neighborhood disadvantage. These negative early life events / exposures at the micro-physical, family, and neighborhood-levels associated, across multiple decades, with subtle and diverse poor brain-related outcomes later in life, including diminished cognitive capacity, increased symptoms of psychopathology, altered epigenetic controls, disadvantageous personality styles, and worse physical health. Results collectively reinforce the view that the early life represents a profound window of vulnerability and opportunity, with a lifespan perspective offering great potential for more efficacious public health research, clinical practice, and policy, as the diseases of the adult likely have roots in the life of the child.