An investigation of the time course of category congruence and priming distance effects in number classification tasks.

The issue investigated in the present research is the nature of the information that is responsible for producing masked priming effects (e.g., semantic information or stimulus-response [S-R] associations) when responding to number stimuli. This issue was addressed by assessing both the magnitude of the category congruence (priming) effect and the nature of the priming distance effect across trials using single-digit primes and targets. Participants made either magnitude (i.e., whether the number presented was larger or smaller than 5) or identification (i.e., press the left button if the number was either a 1, 2, 3, or 4 or the right button if the number was either a 6, 7, 8, or 9) judgments. The results indicated that, regardless of task instruction, there was a clear priming distance effect and a significantly increasing category congruence effect. These results indicated that both semantic activation and S-R associations play important roles in producing masked priming effects.