Recency is Sufficient for Reconciling Categorisation and Memory: Reply to Devraj et al. (2024)

Devraj et al. (Psychonomic Bulletin & Review. doi:10.3758/s13423-023-02448-2, 2024) presented evidence which they claimed demonstrated that people adapt their categorisation strategies to task demands. When items are distributed uniformly across time as is the standard procedure in categorisation experiments, participants initially classify items based on similarity to category prototypes. Over time, as more detailed exemplar representations of categories are formed, people shift towards utilising exemplar-based classification for increased performance. By contrast, if itemsare experienced less frequently over time as is commonly observed in real-world conditions, participants instead seem to initially employ an exemplar strategy and then shift towards prototype classification. By re-analysing the same data, we argue instead that this pattern can be solely understood as differences in accuracy in categorising exception items over time; consequently, the presented evidence is insufficient to distinguish between a strategy-shift and a more parsimonious exemplar-forgetting account. Rule-plus-exception category structures are equally well fit by exemplar and prototype models when exception performance low; however as exception accuracy increases, an exemplar model advantage emerges. As such, while relative model fit could indicate a shift between classification strategies, an exemplar-only strategy can produce identical trends if performance varies. Additionally, although their experimental design successfully introduced a distributional manipulation, this systematically influenced stimulus recency. We found that while a mixture model of strategy-shifting provided a good fit to data, an exemplar-only model sensitive to recency was equally effective. While a strategy-shift remains plausible, we suggest that a single system model provides a more parsimonious account of the present data and can also reconcile the perceived tension between categorisation and memory findings.