Not Just Stimuli Structure: Sequencing Effects in Category Learning Vary by Task Demands

Attention- and memory-based accounts of sequencing effects in category learning are often pitted against one another, but we propose that both are important. We created an unsupervised learning task in which the rules governing categories would be difficult to notice under interleaved sequences. Specifically, participants were presented with Chinese characters and their meanings. Category-related characters all shared a subcomponent ("radical"), but participants had to abstract this rule. No character was repeated. On the day-delayed test, participants were shown new Chinese characters and asked to select a possible meaning to test category induction. Under both passive (Experiment 1) and active (Experiment 2) study, we found no interleaving benefit. However, when we eliminated the demand on attentional processes by directing attention to the rules (Experiment 3), we obtained an interleaving benefit. We discuss implications for how sequencing decisions should not only depend on the stimuli but also the learning task. General Audience Summary Research has shown that generally when learning new categories, it is best to intersperse examples from different categories between one another (e.g., ABCABCABC) rather than show examples from one category at a time (e.g., AAABBBCCC). This finding is called the interleaving effect. In this study, we show that interleaved study may not always confer an advantage over blocked study when learners do not have much information about the categories being learned (i.e., unsupervised learning tasks). Participants were presented with a list of Chinese characters and their meanings and then were shown new characters and asked to guess at their meanings. What learners needed to discover for themselves in Experiments 1 and 2, is that these words fit into "categories" (e.g., water-related: rapids, damp, boil, harbor) and that characters within a category share a common component. We show blocked study (one category at a time) can help learners notice the shared component; interleaving makes it harder. But when learners were alerted to the existence of the rules (Experiment 3), interleaving led to much better performance on the new character identification test. These results highlight the role that sequencing plays not just in driving learners' attention but also facilitating memory and suggests that instructors' and learners' sequencing decisions should depend not only on the category stimuli being learned but also on the specifi