The present study investigates L1 and L2 English speakers' knowledge of the "wh"-clausal construction along the parameters of (a) conventionality, distinguishing between high-frequency conventional and low-frequency unconventional formulations ("I asked him why they agreed/why did they agree"), and (b) proposition type, differentiating between interrogative versus non-interrogative proposition types ("I asked / told him why they agreed"). We also consider the extent to which L2 speakers' constructional knowledge is influenced by learners' target language experience, such as L2 proficiency, context of L2 learning (ESL or EFL), and target language exposure. Results from a judgment task revealed nuances in L1-L2 discriminatory capacities, and more importantly, differences in sensitivity to proposition type between the ESL and EFL group, but no L2 differences in sensitivity to conventionality. L2 proficiency, speakers' length of target immersion experience, and classroom exposure were shown to also impact linguistic sensitivity, highlighting a moderating effect of target language exposure and an important role for classroom instruction.