In addition, it is predicted that reaching movements performed
subsequent to the illusion will reflect the uncertainty suggested by
the unusual illusory content. This latter hypothesis is based on the
idea that expectations regarding the precision of sensory (proprioceptive)
input occurring as movement unfolds affect how
smoothly movement is performed. In short, if proprioceptive
imprecision is expected, movement should be uncertain, exploratory,
and tentative (cf. Friston, Daunizeau, Kilner, & Kiebel, 2010).
Specifically, we expect that individuals with low ASD-like traits
will exhibit less smooth movement after experiencing the illusion
than individuals with high ASD-like traits. Higher order temporal
derivatives of position (e.g., jerk) are of interest to this hypothesis
due to their relationship with movement smoothness. Our previous
study, which found differences between clinical ASD and
control participants in the acceleration of reaching movements
performed following the illusion, was unable to assess comprehensively
differences in movement (such as smoothness) due to
limits of the tracking technique used. The current study therefore
extends previous findings to a nonclinical sample of individuals
with and without ASD-like traits and asks, in particular, whether
the differences in motor parameters could pertain to differences in
expected precisions.