Independent judgment-linked and motor-linked forms of artificial grammar learning.

Three experiments investigated whether a motor-linked measure (string typing speed) and an judgment-linked measure (grammatical judgment of strings) accessed the same implicit learning mechanisms in the artificial grammar learning task. Participants first studied grammatical strings through observation or through responding to each letter by typing it and then performed typing and grammatical judgment tests. Grammatical judgment test performance was better after observation than after respond learning, whereas typing test performance on higher order relations was worse after observation than after respond learning (Experiment 1). Participants transferred grammatical knowledge across letter sets on the grammatical judgment test, but not on the typing test (Experiment 2). Typing speed did not differ for hits (grammatical strings classified by participants as grammatical) and misses (grammatical strings classified as nongrammatical, Experiment 3). These results are consistent with typing and grammatical judgment tests tapping independent mechanisms and indicate that implicit learning may consist of many different forms of learning rather than being a unitary learning mechanism.