Effect of related and unrelated memory loads on the prerecognition visual processing of traffic signs

Prerecognition visual processing of traffic signs was evaluated while subjects maintained one of four different types of memory load: low imageability nouns, traffic sign words, random shapes, or traffic sign shapes. Recall was uniformly high (mean=92%) and did not differ among groups. There was a highly significant interaction among groups (different memory loads), sign messages (Stop, Right, Left, Slow), and sign formats (symbol vs. word). Holding random shapes in memory eliminated prerecognition processing differences among sign messages for symbol format signs. However, for all other memory loads, differences among sign messages were significant. Tests across the memory load conditions for each format of each sign message showed that, for the Stop symbol, the Right symbol, and the Right word signs, the various memory load conditions produced no significant differences. For all other sign messages in both symbol and word format, there were significant differences among memory loads. In summary, these data show that the action message presented in traffic signs is being unconsciously processed within the first few milliseconds of visual processing, and that these operations involve unconscious activation of memory processes that store the meanings of various signs.