Can characters be classified directly as digits vs letters or must they be identified first?

Two experiments were addressed to the question of whether or not Ss can distinguish between letters and digits without identifying the characters. In Experiment I Ss attempted to identify noisy characters; a character was said to be implicitly classified correctly if the identification response, whether correct or incorrect, was in the same category vis-a-vis the letter-digit distinction as the stimulus. Implicit classification of characters for which the identification response was incorrect was very little better than chance. The task in Experiment II was to classify the characters directly. The explicit classification performance in this case was poorer than the implicit classification performance of Experiment I. The results were taken as evidence that Ss could not distinguish between letters and digits unless they could identify the characters.