Mirror neurons and action understanding. Is simulation involved?

The discovery of mirror neurons (MNs) has been hailed as the most important finding of the last decade in neuroscience (Ramachandran, 2000), paving the road for the explanation of diverse phenomena from the evolution of language (Rizzolatti & Arbib, 1998), through imitation (Iacoboni et al., 1999), to intersubjectivity (Gallese, 2003). Here I am concerned with the more modest claim that credits a fundamental role to mirror neurons in understanding observed actions (section 1). In particular, mirror neurons have been argued to support simulation theories of action understanding and mind reading (Gallese & Goldman, 1998; Gallese et al., 2004), an idea that has also been dubbed as the 'direct-matching hypothesis' (Rizzolatti et al., 2001). I shall argue that the evidence published on the response properties of MNs in monkeys is incompatible with these theories of action understanding because (a) MNs' activation reflects not the commencement but the conclusion of action interpretation (section 2), and because (b) MNs do not 'mirror' observed actions with sufficient accuracy for effective simulation (section 3). I shall offer an alternative interpretation, which preserves the MNs' role in action understanding without imposing a simulation function on them (section 4).