A previous effect-of-instruction study (Deconinck et al. 2010) reported on the benefits for word learning of an intervention which prompts learners to evaluate the extent to which a novel word’s meaning is congruent with its form. However, that study did not explore the nature of the thought patterns provoked by this evaluation activity. The present article reports a think-aloud experiment designed to gain insight into these thought patterns. Thirty learners of English as a foreign language were asked to verbalize their thoughts as they performed the task of rating the degree to which they felt the meaning of novel English words was congruent with their form. The participants were found to resort to a variety of associations in order to carry out this task, associations that make use – but also go beyond – traditional notions of prior lexical knowledge, including sound symbolism.