A commonly implied assumption is that lemma retrievals shouldn't interfere with phonological processes (e.g., Schriefers et al., 1990), though it is difficult to know if a speech slowdown is due to a phonological or semantic interference due to our experimental setup.
since in our experiment, effects are still observed at large distances from the target words, either phonological forms can be retrieved in a non-incremental way (possibly even before lemmas for other words are retrieved), or the retrieval of the lemma does interfere with phonological encoding in some way; for instance, by activating related phonological forms.