Categorization processes in mental comparisons

Five experiments explore categorization and category-based congruity effect s in mental comparisons. The first 4 experiments concentrate on categorizat ion of infinite-set small items. The experiments vary the additional items presented and whether those items appear once (Experiments 1-2) or repeated ly (Experiments 3-4). Additional items include other small items (Experimen t 1), relatively large items (Experiments 2-4), and items involving nonsize dimensions (Experiment 4). The critical small items show a complete congru ity effect only in Experiments 1 and 3. Results suggest that categorization of infinite-set items may be based on range information alone (Experiment 1) but that multiple categorizations based on multiple ranges (Experiment 2 ) may require attentional effort. Results implicate categorization as a cen tral process in mental comparison, despite differences in ease of categoriz ation across paradigm.