Rotation size drives heterogeneous explicit strategy development in motor adaptation
Humans rapidly adapt their movements to compensate for changes in the environment, yet how explicit movement strategies emerge during adaptation remains poorly understood. These strategies have traditionally been described by using a smooth, exponential learning curve, suggesting a relatively uniform pattern of strategy development across individuals (Taylor et al., 2014; McDougle et al., 2015). However, recent results suggest substantial variability in how individuals develop explicit aiming strategies, such as abrupt transitions (D'Amario et al., 2024; Townsend et al., 2026), or exploratory periods, or delayed stabilization of compensatory behaviour (Tsay et al., 2024), and some participants never developing a strategy. These findings raise the possibility that smooth group-averaged learning curves may obscure meaningful heterogeneity in individual strategy development. This study therefore examines whether explicit strategy development follows distinct individual-level patterns and whether these dynamics are influenced by perturbation size. Participants completed a visuomotor rotation reaching task where a cursor they controlled with their unseen, right hand was rotated around the home position using one of five perturbations (20, 30, 40, 50, and 60 degrees). Before each reach, participants reported their explicit strategy by aiming an arrow to indicate their planned hand movement direction. Based on previous findings, we hypothesized that participants would exhibit at least three distinct patterns of explicit strategy development emerged: 1) gradual/incremental, 2) stepwise, and 3) exploratory. Instead, participants were distributed along a continuum of strategy development profiles, with different regions along this continuum resembling these previous proposed patterns. Where learners fell along this continuum varied with perturbation magnitude, such that larger rotations associated with greater exploratory behaviour and proportion of strategy-use. Our findings reveal substantial heterogeneity in how explicit strategies emerge during visuomotor adaptation and suggest that smooth group-averaged learning curves may obscure important individual differences in learning dynamics. Notably, perturbation magnitude appears to systematically influence where individuals fall along this continuum, providing a potential mechanism for understanding how explicit strategies emerge and stabilize over time.