Maurício Martins and colleagues tested 40 adults in a finger-movement task in which participants practiced short keyboard sequences guided by visual cues. The sequences followed either iterative rules (adding elements at the same structural level) or recursive rules (embedding patterns within patterns to produce new hierarchical levels). Across two testing days, participants progressed through three phases: copying example sequences (training), judging whether sequences were rule-consistent (discrimination), and finally generating new sequences without visual guidance (generation). Most participants successfully discriminated recursive patterns and produced new hierarchical motor sequences, particularly on the second day. Crucially, learning was strongest when participants first mastered the simpler iterative rule before attempting recursion.

The authors found that recognizing recursive structure alone was not sufficient for producing it: successful motor generation required deeper abstraction of the rules. Performance improved after overnight consolidation, consistent with the role of sleep in forming abstract motor knowledge.

Overall, the study demonstrates that recursion extends beyond language and perception, supporting the idea that humans possess the capacity to build hierarchical structures in action.

Contact: Maurício Martins (University of Vienna, Vienna, Austria)

Email: mauricio.martins@univie.ac.at

Martins, M., Bergmann, Z., Leonova, E., Bianco, R., Sammler, & D., Villringer, A. (2025). Acquisition and utilization of recursive rules in motor sequence generation. Cognitive Science, 49, e70108. https://doi.org/10.1111/cogs.70108