Abstract
<p><meta charset="UTF-8" />Working memory, inhibitory control, and cognitive flexibility are three core components of executive function (Diamond, 2006). It has been suggested that each component develops in early childhood and continues into late childhood (Diamond, 2013). However, the developmental relation of these three components in early childhood remains to be clarified. This study investigated the relation between working memory, inhibitory control, and cognitive flexibility of 5- to 6-year-old children. There were 271 5-year (140 boys; <i>M</i> = 66.79 months, <i>SD</i> =3.95 months) and 215 6-year (123 boys; <i>M</i> = 76.52 months,<i> SD </i>= 3.21 months) Mandarin-speaking children participated in this study. All children received measures of working memory, inhibitory control, cognitive flexibility, short-term memory (forward digit span task, FD), and non-verbal intelligence (TONI-4). “Car-Traffic Light span task” is a complex span task used to measure children’s working memory (the test-retest reliability was .59). The processing task (judging which color differs from the other two) was interleaved with a memory task in which cars appeared in sequence inside a 4 × 4 square grid. Children had to remember this sequence and report it at the end of a list of one to four items. “Picking Fruit task” adapted from Dots task (Davidson, Amso, Anderson, & Diamond, 2006), in which two different fruit pictures (grapes and strawberry) appeared individually and randomly on the left or right side of the screen. Children had to respond (press the keyboard) on the same or opposite side as the picture within 1500ms. Inhibitory control (RT <sub>incongruent</sub> - RT <sub>congruent</sub>) and cognitive flexibility (RT <sub>mixed</sub> - RT <sub>incongruent</sub>) indicators were calculated from the children's responses to task conditions. Test-retest reliability for inhibitory control and cognitive flexibility was .73 and .80, respectively. Analysis of age differences found that 6-year-olds performed significantly better than 5-year-olds on working memory (<i>t</i> = 2.32, <i>p</i> < .001) and inhibitory control (<i>t</i> = 2.29, <i>p</i> < .001), but not on cognitive flexibility. Correlation analysis showed that working memory was significantly associated with age in months (<i>r</i> = .19, <i>p</i> < .001), short-term memory (<i>r</i> = .24, <i>p</i> < .001) and non-verbal IQ (<i>r</i>= .41, <i>p</i> < .001), but inhibitory control and cognitive flexibility were not the cases (only inhibitory control was significantly associated with short-term memory, <i>r</i> = .18, <i>p</i> = .006). In addition, neither inhibitory control nor cognitive flexibility was significantly related to working memory, but inhibitory control was significantly associated with cognitive flexibility (<i>r</i> = - .46, <i>p</i> < .001). Factor analysis found that working memory, short-term memory, and non-verbal IQ have the same components but differ from inhibitory control and cognitive flexibility. These findings suggest that between the ages of 5 and 6, there is a significant improvement in working memory and inhibitory control. Five- to six-year-old children's working memory development is related to their age in months and other cognitive abilities but not to their development of inhibitory control and cognitive flexibility. In contrast, inhibitory control and cognitive flexibility development in children aged 5 to 6 are not dissociated.</p>