A developmental study of the category effect in visual search.

Several studies have demonstrated that adults display a category effect in visual search paradigms. That is, when searching an array for the presence of a target letter, subjects detect the letter faster when the array is composed of numbers rather than letters, and vice versa. Groups of 8-year-olds, 10-year-olds, and adults searched for the presence of a target in fields of items that were either of the same or a different category (letter or number) than the target. Highly significant category effects were evident in the search times of all 3 age groups. While search times were found to decrease with development, there was no evidence of an increasing effect of category with age. It was concluded that the feature extraction process that mediates the category effect is fully automated by age 8.