Abstract: This study recruited 243 children ranging from 10 to 18 years of age to investigate the role of working memory and processing speed in the development of fluid intelligence. Confirmatory factor analysis and structural equation modeling indicated that there are strong correlations between working memory, processing speed and fluid intelligence constructs. However, nearly all of the age-related improvements in fluid intelligence are accounted for by developmental changes in working memory, which also greatly account for the magnitude of age-related increase in processing speed. Moreover, age-related increases in speed don’t mediate age-related improvements in fluid intelligence directly or indirectly when the role of working memory in the development of fluid intelligence has been considered. The results suggested that children’s working memory underlies the development of fluid intelligence while processing speed may be related to individual differences in fluid intelligence.

Key words: fluid intelligence, processing speed, working memory, children