A task was developed to differentiate the reasoning of elementary school students in fifth, sixth, and seventh grades. Subjects completed 16 matrices containing two, three, or four dimensions and varying in the embeddedness of the dimensions. They also solved a formal operational task assessing ability to isolate, exclude, and include variables.…

The role of content in formal operations tasks was explored in research that systematically varied the content of tasks and children's performance by developmental level and socioeconomic status (SES). Subjects were 110 Icelandic 12-year-olds who had entered a longitudinal study when they were 7 years old. Two extreme ability groups of children…