Mental-content verbs such as think, believe, imagine and hope seem to pose special problems for the young language learner. One possible explanation for these diYculties is that the concepts that these verbs express are hard to grasp and therefore their acquisition must await relevant conceptual development. According to a diVerent, perhaps complementary, proposal, a major contributor to the diYculty of these items lies with the informational requirements for identifying them from the contexts in which they appear. The experiments reported here (...) explore the implications of these proposals by investigating the contribution of observational and linguistic cues to the acquisition of mental predicate vocabulary. We Wrst demonstrate that particular observed situations can be helpful in prompting reference to mental contents, speciWcally, contexts that include a salient and/or unusual mental state such as a false belief. We then compare the potency of such observational support to the reliability of alternate or concomitant syntactic information (e.g., sentential complementation) in tasks where both children and adults are asked to hypothesize the meaning of novel verbs. The Wndings support the eYcacy of false belief situations for increasing the saliency of mental state descriptions, but also show that.. (shrink)