Although there is substantive evidence of implicit learning (without intention or awareness) of form to form mappings in cognitive psychology, findings in the field of second language acquisition have been inconclusive. This study we report investigated the possibility of adults acquiring a second language morphosyntactic rule implicitly. For the experiment, 65 adult native speakers of English without formal training in language sciences were randomly assigned to one of three groups, (two experimental and one control). There were two conditions in the training session: noun-determiner (N-D), and adjective-determiner-noun combinations (A-D-N). Within each condition, the determiner is attached to one of the nouns, either the subject or the object. Each noun to which the determiner is attached is either a person (Anna, Tom, Hank, Sara, etc.) or not a person (zebra, gorilla, elephant, horse, broom, door, stroller, etc.). In a session lasting 60 minutes, subjects were trained on 120 stimulus sentences, each containing two noun phrases (one containing a determiner, one consisting of a proper name), with length and other potential confounds controlled for. The amount and nature of resulting learning were assessed using accuracy on a speeded grammaticality judgment test with all novel stimuli not previously encountered in the training session, reaction times, confidence ratings and judgments of source of knowledge.