Usage-based theories hold that mental representation of language is shaped by a lifetime of usage. Both input to which first language (L1) and second language (L2) users are exposed and their own language production affect their construction learning and entrenchment. The present study investigates L2 users' knowledge of two introductory-"it" variants, Adj-that (e.g., "it is clear that"...) and Adj-to (e.g., "it is difficult to"...). We probed the extent to which adjective-variant associations in an academic section of COCA and L2 users' engagement with academic writing affected learners' generation of adjectives distinctively attracted to the two variants. An analysis of cue-outcome contingency was conducted to establish adjective-variant associations, and an elicitation task was carried out, probing L2 users' ability to generate adjectives when prompted with the variants (e.g., "it is [blank] to"). The participants were 84 graduate students in the United States, 44 from L1 English and 40 from L1 Thai backgrounds. The results indicated that the adjective-variant associations predicted L2 users' generation of adjectives. However, academic writing engagement did not affect learners' performance. The findings suggest that statistical information in the input affects L2 users' constructional representation.