The pretesting effect refers to the finding that guessing the answers to test questions before learning the correct answers improves memory relative to studying (or reading) without prior guessing. Although the pretesting effect is robust and has been demonstrated across multiple studies, its magnitude varies across individuals. Two studies investigated whether individual differences in working memory capacity (WMC), episodic memory ability (EM), and/or fluid intelligence (gF) help explain that variation. In Study 1, lower gF scores were associated with a larger pretesting effect among undergraduate students, stemming from lower performance on read items. In Study 2, involving adult online participants, observed patterns were less consistent, but lower WMC scores were associated with larger pretesting effects, again due to lower performance on read items. Together, these patterns suggest that pretesting can homologize memory ability across individuals, although to an extent that may vary across learner populations and cognitive abilities. That conclusion and other findings are interpreted in the context of relevant individual differences research and theories related to pretesting and memory phenomena.