 Armed with their Official Recipe, Polger and Shapiro next seek to dismiss the evidence commonly put forward by proponents of multiple realization as arguments for functionalism or realization-physicalism over mind-brain identity theory. They first consider “direct evidence”, empirical cases presented as genuine instances of multiple realization of the mental on the physical. One type is “cortical functional plasticity”, in both “common” and “radical” varieties. A “common” kind is cortical reorganization, where neurons in a specific cortical region take on a new function following damage to nerves or axons providing their normal input. A more “radical” variety is exemplified by the well-known work in developing ferrets, in which retinal projections were redirected to the medial, rather than the lateral geniculate nucleus in the thalamus, and hence retinal input was projected to auditory, rather than visual cortex (see the discussion of Shapiro 2008 in  §3.2  above). Polger and Shapiro argue that both of these varieties fail to meet at least one condition of their Official Recipe, so neither counts as a genuine instance of mental-to-physical multiple realization. The “common” case involves change in function—in the specific example, neuronal activity in the reorganized region of primate somatosensory cortex now represents stimulation to a different region of the monkey’s hand. In the “radical” ferret rewiring case, the visual capacities of the experimental ferrets’ auditory cortex, compared to those of intact control ferrets, differ significantly, e.g., the experimental ferrets show significantly deficient performances on visual discrimination tasks compared with controls’ performances.