What Observation of Motor Skills Does and Does Not Teach Us

We review data from 4 experiments where we have been studying what is learnt through observation. In these experiments people learnt to reach in a distorted visual-motor, virtual environment. In all experiments observers successfully adapted to new visual-motor environments just by watching. Importantly, however, they adapted differently to actors. At no time did naïve observers show after-effects when returned to a known normal environment. However, if observers had previously practiced in this environment, after-effects were subsequently seen following an observation phase. Further, again different to actors, they showed good retention and lack of interference when performing in two opposing environments. We argue that observation does not result in the updating of an internal (motor) model, that it is primarily strategically mediated and that only after physical experience in the environment can ‘motor-simulation’ through observation take place.