Implicit learning of color-word associations using a Stroop paradigm.

Our experiments asked whether implicit learning occurs for novel nonverbal associations. We presented subjects with color names printed in incongruent colors; subjects were asked to name the color in which the word was printed. In Experiment 1, each of 7 color words were associated with the same incongruent color across 6 blocks of trials, and then the color-word associations were abruptly changed. Both control subjects and patients with amnesia reduced their color-naming times across the first 6 trial blocks, and naming times increased when the color-word associations were changed. In Experiment 2, similar results were obtained when neutral words were associated with colors. In Experiment 3, we found that naming times were not disrupted when an irrelevant dimension (typecase) was changed. Finally, in Experiment 4, we found that the effect persisted across a 5-min delay. These studies provide evidence that implicit learning occurs for nonverbal associations and is independent of the brain structures damaged in amnesia.