Despite the real-life application, little research has been done examining the impact of stress on category learning. For example, how does stress impact different types of category learning and consolidation, specifically rule-based and information-integration? A study was conducted with 123 undergraduate college students to compare the impact of stress on learning and consolidation for explicit and procedural learning systems. Approximately half of the participants were stressed on session one using the Trier Social Stress Test (TSST) and then given a rule-based (RB) learning task (29 participants) or an information-integration (II) learning task (30 participants). The other half of the participants completed the TSST control condition and a RB learning task (32 participants) while another 32 participants completed an II task. Five cortisol samples were obtained from each participant on session one. To examine consolidation, participants were asked to return for a second session the following day to complete the same category-learning task again (without the stress).

Analysis of the data showed a significant detriment in accuracy for the RB condition as cortisol increased throughout the task, which was replicated with the COVIS model of category learning. This finding was expected within the RB task since stress impairs working memory and decreases long-term potentiation. For the II condition, participants were separated into three different cortisol levels (not conditions), and those who had the lowest accuracy were those whose cortisol levels remained stable across the study. Within the II task, however, the impairment is likely due to the increased rule-use of those within the middle cortisol group, which could suggest a competition between the two systems. This finding was also replicated with the COVIS model. Furthermore, these trends continued into session two.