Motor Signatures of Digital Intention: A 3D Kinematic Analysis of Smartphone Typing Behaviors

This study investigated how different digital experience and task intention influence touchscreen typing performance, kinematics, and strategy in smartphone users. Building on principles of motor learning and embodied cognition, Digital Immigrants (DI; born before 1980) and Digital Natives (DN; born 1980 or later) were compared while typing sentences in two tasks: WhatsApp Chat (content generation and communication) and Google Search (content consumption and information retrieval). Thumb movements during consecutive keypresses were captured using 3D motion tracking, while letter-matching accuracy was confirmed and typing errors excluded through video-based validation. Kinematic analysis revealed that DNs exhibited a higher-vigor motor execution profile than DIs, characterized by generally faster movements. Differences in movement timing were also observed, with DNs showing later peak deceleration relative to DIs. Contextual differences also emerged: typing in WhatsApp was typically faster and more forceful (e.g., higher peak velocities and steeper deceleration) compared to Google typing, consistent with more dynamic motor execution during socially driven communication. Crucially, the timing of maximum deceleration revealed a three-way interaction between group, task, and hand, indicating that motor efficiency is modulated by both digital experience and contextual demands. Collectively, these findings demonstrate that different task intention and digital experiences fundamentally shapes fine-grained sensorimotor skills. DNs demonstrated faster and more vigorous thumb movements, suggesting greater sensorimotor efficiency due to early and sustained touchscreen use. In contrast, DIs, while less kinematic efficient, appeared to adopt more cautious motor patterns, possibly reflecting compensatory strategies when interacting with unfamiliar digital interfaces. These findings highlight how sensorimotor histories influence digital fluency and the embodied nature of digital intention in modern touchscreen use.