One cannot directly record the activity of mirror neurons in human participants; it would be totally inappropriate to implant electrodes in people's brains. So, to study the mirroring system in humans one has to find what computer people call a work-around. In one ingenious work-around, Giovanni Buccino and his colleagues (2005) used a method called Transcranial Magnetic Stimulation (TMS) to stimulate briefly and gently (from outside the skull) the parts of the brain known to be directly responsible for initiating actions. For instance they could stimulate the part of the brain responsible for making hand movements and record the electrical activity of the muscles of the hand that resulted. The could do the same for foot movements. What would happen now, the researchers asked, if the human participants were stimulated in this way and at the same time were asked to listen to three-word sentences that concerned making either a movement of the hand such as "Suonava il piano" (He played the piano) or of the foot such as "Calciava la palla" (He kicked the ball). What they found was that when the participants listened to sentences concerning hand movements, the electrical activity recorded in the hand muscles in response to the transcranial stimulation was reduced. This reduction did not occur when participants listened to sentences about foot movements or sentences that did not indicate movement. Similarly, when listening to sentences about foot movements, the stimulation-elicited electrical activity in the foot muscles was reduced as compared to the activity that occurred when listening to sentences about the hand or to sentences that were not about movement. The reduction of electrical activity in the hand or foot muscles in response the stimulation occurred because the parts of the brain concerned with initiating hand or foot movements were already occupied with the understanding the sentences that concerned those particular movements.
When we understand a sentence there is activation of the areas of the brain concerned with hearing and language. The finding of Buccino and his colleagues showed that, in addition, when sentences were about actions, there were also measurable effects in the areas concerned with making the same actions. Extending the idea, members of the same research group (Glenberg et al., 2008) found comparable effects while people read sentences that were about either physical transfer of something away from the person (e.g. "You give the papers to Marco"), or abstract transfer for instance (e.g. "You delegate the responsibilities to Anna"), but not when the transfers were in the opposite direction (towards the subject).
The researchers interpret their findings in terms of mirror neurons. Recognition of an action, even in the imagination when we hear or read about it, and even when a sentence is about transfer of something non-material, involves brain systems responsible for initiating that action. The researchers also link the effects of non-material transfer to theories of metaphors as based on embodiment (Lakoff & Johnson, 1980).
For the psychology of fiction, the implication is that when we read, or go to the theatre or cinema, and identify with a character, and when we put ourselves in his or her shoes (almost not a metaphor), we partly enact what that character is doing. It is in that way, perhaps, that we come to understand within ourselves (at least partly) the actions about which we read. I wonder whether, as Elaine Scarry (1999) has proposed, that the particular way in which a writer portrays an action makes a difference to the vividness with which we imagine it and embody it in ourselves.
G. Buccino, L. Riggio, G. Mellia, F. Binkofski, V. Gallese, & G. Rizzolatti (2005). Listening to action-related sentences modulates the activity of the motor system: A combined TMS and behavioral study. Cognitive Brain Research, 24, 355-363.
A. Glenberg, M. Satao, L. Cattaneo, L. Riggio, D. Palumbo, & G. Buccino (2008). Processing abstract language modulates motor system activity. Quarterly Journal of Experimental Psychology, 61, 905-919.
G. Lakoff & M. Johnson (1980). Metaphors we live by. Chicago: Chicago University Press.
G. Rizzolatti, L. Fadiga, V. Gallese & L. Fogassi, L. (1996). Premotor cortex and the recognition of motor action. Cognitive Brain Research, 3, 131-141.
E. Scarry (1999). Dreaming by the book. Princeton, NJ: Princeton University Press.