StimulationIn addition to action un

Stimulation
In addition to action understanding and action identification, the mirror system seems to support the prediction of future action outcomes (action simulation). In particular, matching observed actions to one’s own action repertoire allows one to exploit mechanisms in the motor system that are normally used to predict the outcomes of one’s own actions. This solution is more parsimonious than predicting the results of others’ actions based on a separate perceptual-anticipation mechanism. In support of simulation, it was found that people observing someone throwing a dart could quite accurately predict where the dart would land. Importantly, the predictions of the landing position were most accurate when participants observed videos of themselves throwing the dart, although recording session and recognition session were at least 1 week apart. This makes it very unlikely that the higher accuracy for self was due to memories for the outcome of particular throws (Knoblich & Flach, 2003). The higher degree of similarity between a perceived action and the way one would perform it oneself led to the higher prediction accuracy for oneself than for others.
There is also reason to believe that proprioceptive signals (sensing position of body parts) andtactile signals from one’sown body contribute to action simulation. A recent study showed that lacking these signals impairs action understanding ( Bosbach, Cole, Prinz, & Knoblich, 2005). In this study, two de-afferented individuals were tested. De-afferentation refers to the loss of body sense due to a degeneration of all nerve fibers that normally transmit sensory information to the brain. The two individuals observed videos of an actor lifting a box. Prior to lifting the box, the actor had sometimes been told the correct weight of the box and had sometimes been deceived about its weight. Both individuals had difficulties telling whether the actor lifting the box had the right or wrong expectation about its weight. In contrast, healthy participants had no problems making these judgments. They could tell from the actor’s body posture and body movements whether or not the actor had been deceived, suggesting that action simulation in healthy individuals is supported by peripheral bodily signals. The lack of peripheral bodily signals in the de-afferented patients resulted in faulty simulations.