In testing human participants’ processing of identity and nonidentity stimulus relations, identity matching (IM) trials and nonidentity, conditional matching (CM) trials served as practice. Test cycles consisted of IM probe trials introduced within CM baseline trials (CM/IM) and CM probe trials within IM baseline trials (IM/CM). Twenty-one participants responded to computer-generated stimuli using a keyboard. The results replicate and extend those of D’Amato, Salmon, Loukas, and Tomie (1986) to human participants. Differences in probe and baseline response times in the IM/CM and CM/IM test cycles support the conclusion that humans process IM and CM in different ways, as D’Amato et al. concluded for monkeys but not for pigeons.