Image generation in a letter-classification task

Subjects classified briefly presented uppercase letters as belonging to the first or second half of the alphabet. A prior alternative preceded each target letter by 200 or 1,400 msec. It was either an ampersand (control), a lowercase letter (opposite case), or an uppercase letter (same case). In the latter two conditions, the target was equally likely to be identical in name to the prior alternative or from the opposite half of the alphabet. For the 200-msec onset asynchrony, classification accuracy was greater in the same-case condition than in the other two conditions, which did not differ. For the 1,400-msec onset asynchrony, accuracy in both the same- and opposite-case conditions was greater than accuracy in the control condition. Same- and opposite-case prior alternatives always biased subjects toward classifying the target in the same half of the alphabet as the alternative. The accuracy results suggest that internally generated images can be used to aid target classification in the opposite-case condition.