Global probabilities take precedence over transitional probabilities in predicting learning outcomes

Humans implicitly extract statistical regularities from sensory input across multiple perceptual dimensions. In audition, both transitional probabilities (relationships between successive sounds) and global probabilities (overall frequency of occurrence) shape perception. While each has been extensively studied in isolation, their combined influence remains less understood, especially in active tasks. Here, we investigated how these two forms of statistical structure jointly influence perceptual judgments. Participants heard a 70 ms cue tone followed by a 50 or 90 ms target tone and judged whether the target tone was short or long. Crucially, statistical regularities were embedded along a task-irrelevant dimension: tone frequency. This allowed us to assess how implicit statistical learning unfolds when regularities are orthogonal to task goals. Across three experiments, high transitional probabilities between cue and target frequencies facilitated faster duration judgments, independent of whether frequencies matched. High global probability also sped responses. However, when both regularities co-occurred, the effect of transitional probability is eliminated. Additionally, a direct sensory match between cue and target frequencies provided no perceptual advantage. These findings demonstrate that, even in active tasks demanding attention to a specific dimension, listeners implicitly learn statistical structure along irrelevant dimensions. While both transitional and global probabilities shape perception, global regularities dominate when statistics co-occur. This work advances our understanding of how layered statistical regularities guide behavior in goal-directed listening contexts.