How do people discover an effective movement strategy when the environment abruptly changes—such as
when using the trackpad on an unfamiliar laptop? Strategic adaptation is often described as a reinforcement
learning process characterized by two key features: random exploration followed by gradual error reduction.
We propose a different view in which strategic adaptation operates through hypothesis testing: learners
generate specific action–outcome hypotheses about the environmental change, discount those that conflict
with feedback, and continue testing alternatives until they discover the correct rule. To adjudicate between
these accounts, we conducted two large-scale experiments using a visuomotor rotation task designed to
isolate strategic adaptation under different target arrangements (N = 560). Individual learning trajectories
showed pronounced exploration but were far from random, exhibiting structured, multimodal error
distributions. Moreover, participants did not converge on the solution gradually; instead, they discovered it
abruptly. Critically, strategic adaptation depended on target arrangement: some configurations steered
participants toward the correct rotational hypothesis, whereas others led them to alternate between
rotational and translational hypotheses. Together, these findings position hypothesis testing as a core
mechanism governing strategic motor learning.