More is generally better: Higher working memory capacity does not impair perceptual category learning

It is sometimes supposed that category learning involves competing explicit and procedural systems, with only the former reliant on working memory capacity (WMC). In 2 experiments participants were trained for 3 blocks on both filtering (often said to be learned explicitly) and condensation (often said to be learned procedurally) category structures. Both experiments (total N = 160) demonstrated that participants with higher WMC tended to be more accurate in condensation tasks, but not less accurate in filtering tasks. Furthermore, state-trace analysis did not find a differential influence of WMC on performance in these tasks. Finally, inspection of the mixture of response strategies at play across the 2 conditions and 3 blocks showed only a minor influence of WMC, and then only on later training blocks. The results provide no support for the existence of a "system" of category learning that is independent of working memory and are instead consistent with most single-system interpretations of category learning.