Studies of unconscious plagiarism have reported that peoplemistakenly include a partner’s responses when trying to recalltheir own (recall-own task) and include own responses whentrying to recall their partner’s (recall-partner task). In a simula-tion, we tested if participants’ memory performance at test, in-cluding source errors, can be explained by participants simplyguessing items that come easily to mind. We show that guess-ing alone cannot account for the pattern of data participantsshow at test. Modifying the simulation by including memoryfor self-generated items allows us to replicate the pattern of re-sponding in the recall-own but not the recall-partner task, evenwhen we assume that participants in the recall-partner taskstrategically withhold more fluent items from report. This sug-gests that judgements of items’ memory strength alone cannotexplain performance in the unconscious plagiarism paradigm.