Atypical basic movement kinematics in autism spectrum conditions

Individuals with autism spectrum conditions have difficulties in understanding and responding appropriately to others. Additionally, they demonstrate impaired perception of biological motion and problems with motor control. Here we investigated whether individuals with autism move with an atypical kinematic profile, which might help to explain perceptual and motor impairments, and in principle may contribute to some of their higher level social problems. We recorded trajectory, velocity, acceleration and jerk while adult participants with autism and a matched control group conducted horizontal sinusoidal arm movements. Additionally, participants with autism took part in a biological motion perception task in which they classified observed movements as ‘natural’ or ‘unnatural’. Results show that individuals with autism moved with atypical kinematics; they did not minimize jerk to the same extent as the matched typical control group, and moved with greater acceleration and velocity. The degree to which kinematics were atypical was correlated with a bias towards perceiving biological motion as ‘unnatural’ and with the severity of autism symptoms as measured by the Autism Diagnostic Observation Schedule. We suggest that fundamental differences in movement kinematics in autism might help to explain their problems with motor control. Additionally, developmental experience of their own atypical kinematic profiles may lead to disrupted perception of others’ actions.