Contextual cues and transition statistics drive expression of competing motor memories

Learning multiple motor skills and expressing them appropriately in changing environments is challenging. While contextual cues help separate these memories, their interaction during retrieval remains unclear. We investigated how memory stability, recency, and transitional statistics of learning environments influence this process. Across six visuomotor adaptation experiments, participants learned opposing rotations linked to distinct cues under blocked or interleaved schedules and were tested in stable or dynamic environments. We found that contextual cues separated memories, but expression was biased toward stable memories after imbalanced training and toward recent ones when memory stability was equal. When training and testing statistics mismatch, cue-based retrieval failed, and behavior biases toward stability or recency. Conversely, high-entropy, interleaved training enabled appropriate, cue-based expression across testing conditions. These findings demonstrate that memory retrieval arises from arbitration between cues and learned transition priors, offering a unified framework that explains interference, recovery, and the benefits of variable practice.