Equally divided by sex and distributed equally across fourth/fifth, eighth/ninth, and college grade levels, 144 subjects performed a mental rotation task under instructions emphasizing either accuracy or speed of response, or both. Instructions had large and consistent effects on speed of response but were not as uniformly effective in their…

In two experiments, 168 subjects aged 8-22 years performed visual search and memory search tasks (experiment 1) or memory search, mental rotation, analogical reasoning, and mental addition tasks (experiment 2). Increases with age in speeds of visual and memory search were described well by exponential functions. (SKC)