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The development of numerosity estimation: Evidence for a linear number representation early in life
(2015)
Several studies investigating the development of approximate number representations used the number-to-position task and reported evidence for a shift from a logarithmic to a linear representation of numerical magnitude with increasing age. However, this interpretation as well as the number-to-position method itself has been questioned recently. The current study tested 5- and 8-year-old children on a newly established numerosity production task to examine developmental changes in number representations and to test the idea of a representational shift. Modelling of the children's numerical estimations revealed that responses of the 8-year-old children approximate a simple positive linear relation between estimated and actual numbers. Interestingly, however, the estimations of the 5-year-old children were best described by a bilinear model reflecting a relatively accurate linear representation of small numbers and no apparent magnitude knowledge for large numbers. Taken together, our findings provide no support for a shift of mental representations from a logarithmic to a linear metric but rather suggest that the range of number words which are appropriately conceptualised and represented by linear analogue magnitude codes expands during development.
Objective: To investigate the association of the neuropeptide Y (NPY) promoter polymorphism rs16147 with body mass index (BMI) during the course of development from infancy to adulthood.
Design: Longitudinal, prospective study of a German community sample.
Subjects: n = 306 young adults (139 males, 167 females).
Measurements: Participants' body weight and height were assessed at the ages of 3 months and 2, 4.5, 8, 11, 15 and 19 years. NPY rs16147 was genotyped.
Results: Controlling for a number of possible confounders, homozygote carriers of the rs16147 C allele exhibited significantly lower BMI scores when compared with individuals carrying the T allele. In addition, a significant genotype by age interaction emerged, indicating that the genotype effect increased during the course of development.
Conclusions: This is the first longitudinal study to report an association between rs16147 and BMI during childhood and adolescence. The finding that this effect increased during the course of development may either be due to age-dependent alterations in gene expression or to maturation processes within the weight regulation circuits of the central nervous system.