When two types of stimuli are mixed in a trial block, each stimulus type is typically responded to more slowly than when those stimuli are presented by themselves in pure blocks (a “mixing cost,” [Los, 1996]). In word/non-word naming tasks, however, mixing two types of stimuli leads to a different, “homogenization,” pattern. There is a mixing cost for the easier stimuli and a mixing benefit for the more difficult stimuli ( [Lupker et al., 1997]). In the present research we investigated the generality of this homogenization pattern by examining picture naming and a sum-naming task involving addition problems (e.g., 10+7=?). In Experiments 1 and 2, the homogenization pattern was observed for both pictures and sums. In Experiments 3 and 4, qualitatively different stimulus types (words and pictures, words and sums) were mixed. The mixing cost pattern was observed. Experiments 5 (words and pictures) and 6 (words and sums), however, demonstrated that a homogenization-type pattern can be obtained even when qualitatively different stimulus types are mixed. These results indicate that theoretical mechanisms like those proposed by [Los, 1996] and theoretical mechanisms like those proposed by [Lupker et al., 1997] are both active in reaction time experiments.