The pace at which new words are acquired is influenced by the degree of engagement with them on the part of the learner. Insights from cognitive linguistics into the non-arbitrary aspects of vocabulary can be turned into stimuli for such engagement. The majority of Cognitive Linguists' proposals for vocabulary teaching aim at helping learners appreciate the way a single word form can develop different meanings. This, however, presupposes knowledge of the 'basic' meaning of that word. This article reports an experiment in which learners under an experimental treatment were stimulated to consider the possibility that the form-meaning link in target words might not be fully arbitrary. The mnemonic effect of this task-induced engagement was assessed in relation to comparison treatments in immediate and delayed post-tests measuring both receptive and productive knowledge. Results show that simply prompting learners to evaluate the form-meaning match of words can foster vocabulary acquisition, although not all target words lends themselves equally well to this type of engagement.