Abstract
Some of the neural substrate underlying visuo-motor coordination contributes to the interpretation of action intentions of others. In monkeys this “mirror neuron system” consists of about 30% strictly congruent neurons (they code both the action goal [e.g., grasping an object] and the means for achieving it [e.g., with a precision grasp]) and about 60% broadly congruent neurons (they also fire when observed and performed grasp differ). Here we provide behavioural evidence consistent with rapid and automatic operation of strictly congruent mirror neurons during action simulation in humans.
Observers viewed pictures of object pairs (one large and the other small) in front of a hand that briefly adopted either a power or precision grasp. After a random delay (variable from 0–450 ms), a target appeared unpredictably over one object (e.g., a power grasp was followed equally often by a target over the small/incongruent or large/congruent object). After both 200 ms and 300 ms delays, observers detected targets faster near the object that would be picked up with the previously shown grasp, indicating rapid and spontaneous action simulation. In Experiment 2, 21 new observers saw grasp postures that were only 20% predictive of the star's location (e.g., a power grasp was followed in 80% of trials by a target over the small object). They attended to the grasp-incongruent object within 100 ms following grasp cue offset, indicating strategic cue use. After 300 ms, however, attention was at the grasp-congruent object, indicating that action simulation overruled temporary grasp-object associations.
These results show that observers rapidly infer the goal object of another person's intended action and direct their own attention to it. The ability to interpret different grasps in this way implies the presence of strictly congruent mirror neurons in the human brain.
Sponsored by The Nuffield Foundation