We used a Deese-Roediger-McDermott false memory paradigm to compare Spanish words in which the phonetic realization of /s/ can vary (word-medial positions: bu[s]to ~ bu[h]to ‘chest’, word-final positions: remo[s] ~ remo[h] ‘oars’) to words in which it cannot (word-initial positions: [s]opa ~ *[h]opa ‘soup’). At study, participants listened to lists of nine words that were phonological neighbors of an unheard critical item (e.g., popa, sepa, soja, etc. for the critical item sopa). At test, participants performed free recall and yes/no recognition tasks. Replicating previous work in this paradigm, results showed robust false memory effects: that is, participants were more likely to (falsely) remember a critical item than a random intrusion. When the realization of /s/ was consistent across conditions (Experiment 1), false memory rates for varying versus non-varying words did not significantly differ. However, when the realization of /s/ varied between [s] and [h] in those positions which allow it (Experiment 2), false recognition rates for varying words like busto were significantly higher than those for non-varying words like sopa. Assuming that higher false memory rates are indicative of greater lexical activation, we interpret these results to support the predictions of exemplar theory, which claims that words with heterogeneous versus homogeneous acoustic realizations should exhibit distinct patterns of activation.