Abstract: An impressive human talent is the ability to acquire complex structures and regularities in the surroundings implicitly. Indeed, it is this cognitive ability that has prompted a host of noted researchers to raise some questions about the nature of the implicit learning. It is repeatedly revealed that implicit (incidental) learning had its superiority over explicit (intentional) learning when participants were carrying out the artificial grammar learning task. Specifically, memorization instruction induced better classification performance than rule-searching instruction. There currently is debate, however, whether this implicit learning superiority is due to the specific contribution of unconscious structural knowledge, i.e., guess or intuition. That is, whether the contribution of unconscious structural knowledge is limited to incidental learning, or it can be applied generally to all situations, including intentional learning under rule-searching instructions?
To tackle this issue, the present study examined the contribution of conscious and unconscious structural knowledge for incidental and intentional learning by structural knowledge measurement. A 2 learning mode (incidental vs. intentional) between-subject design was adopted. During the learning phase, participants were presented with 144 letter strings which were generate from a finite-state grammar under two learning conditions. Incidental learning group was required to memorize each string, whereas intentional learning group was asked to search the rule underlying the strings. After that, they were asked to classify a new set of strings according to whether the string followed the same pattern or structure as the strings presented before.
It turned out that: 1) incidental learning group exhibited significantly better performance than intentional learning group, indicated implicit learning superiority, 2) the accuracy of intuition responses for incidental learning group was significantly higher than intentional learning group, which implied a specific contribution of intuition to implicit learning superiority.
To conclude, this finding gave a plausible answer to aforementioned question. The contribution of unconscious structural knowledge is limited to incidental learning, which leads to implicit learning superiority.

Key words: intuition, implicit learning superiority, structural knowledge