Categorical encoding of decision variables in orbitofrontal cortex
Fig 3
Two examples of how the ΔR2 metrics can fail.
(A,B) A dip in the distribution of ΔR2 does not necessarily imply categorical encoding. The clustering algorithm yields two clusters. However, the analyst might have erroneously concluded that there are three variables, including two variables located in the tips of the banana cloud (red and black). The dip in the ΔR2 histogram suggests that these two variables are encoded by categorically distinct populations, but this is in fact not the case. (C,D) Categorical encoding does not always result in a dip in the distribution of ΔR2. In this case, we assume that the analyst correctly concluded that there are two variables, but might have defined these variables such that one is on the north pole (gray) and the other is on the east end of the banana cluster (black). Inspection of the ΔR2 histogram does not reveal any dip. The reason is that data points on the west end of the banana cluster are equally far from the two variables.