Sex differences in the end-state comfort effect in pre-adolescent children

Abstract

There has been recent interest in the developmental trajectory of the end-state comfort effect (ESCE) in young children. However, potential sex differences have yet to be examined in the overturned glass task. We examined the ESCE using this task in a large sample (N=232) of typically-developing elementary school children (111 girls, 121 boys) in grades 1–5 (approximately 7–11years old). We sought to determine whether there were similarities or differences in performance between boys and girls. Children picked up an overturned drinking glass from a table, turned the glass upright, and then poured water into it from a measuring cup. Three trials were performed, and the use of an initial awkward thumb-down grip to pick up the glass was taken as evidence for the ESCE. There were non-significant main effects for sex and grade, but a significant interaction between factors. Boys increased in sensitivity to end-state comfort across the five grades while girls showed a decrease from grades 1–3, followed by an increase between grades 3 and 5. Taken together, the results indicate the presence of adult-like motor planning for the overturned glass task by the 4th grade (i.e., age 10), but also suggest the presence of a motor reorganization in girls, at around the 2nd or 3rd grade (i.e., 8 or 9years of age).