Motor sequences resist automatization as attentional demands increase with sequence learning

Automatization of motor sequences involves a shift from effortful, attention-dependent control to fluent performance through practice. This study examined how learning cues and instructions influence the development of sequence-specific automatization using a modified serial reaction time task with temporally spaced stimuli. Participants practiced a training sequence across ten sessions under four conditions varying in instruction (intentional vs. incidental) and visual cues (present vs. absent). Performance was assessed before and after training under single- and dual-task conditions for trained and control sequences. Results demonstrated robust sequence learning, with faster reaction times for trained than control sequences. Intentional instruction enhanced learning, particularly with visual cues. Contrary to expectations, dual-task costs decreased for the control sequence but increased for the trained sequence. Sequence-specific dual-task costs were associated with superior learning and explicit knowledge, suggesting that deeper sequence encoding may prolong attentional demands despite extensive practice.