The Effect of Perturbation Variability on Sensorimotor Adaptation Does Not Require an Implicit Memory of Errors

In a recent paper1 entitled, "An implicit memory of errors limits human sensorimotor adaptation" Albert and colleagues presented a model in which the adaptive response of the sensorimotor system is flexibly modulated by recent experience, or what they refer to as a "memory of errors". This hypothesis stands in contrast to prevailing models in which automatic and implicit responses to movement errors are relatively insensitive to the statistical properties of the environment2-6. A prime example of this rigidity is that the adaptation system exhibits a saturated response to large errors, resulting in a non-linear motor correction function, a feature that is independent of experience4,5,7. Here we show that the key results reported in Albert et al. are fully explained by presupposing this rigid "motor correction" function without reference to memory-dependent changes in error sensitivity. As such, the evidence presented in Albert et. al. does not support the claim that the history of errors modulates implicit adaptation.