It is important to note the difference between the relationship Ss′ = Ru′ and the severity index (SI) = Ru′/Ra′, where Ss′ is the normalized value of the severity of autism taken from the NEPSYS theory of mind scale, and SI is a theoretical construct established for the purpose of demonstrating the equivalence between the theoretical and empirical models discussed above in establishing the significance of the oxytocin receptor in autism. Here, OXTR is linked to autism.