“…One obvious resolution would be to accept the fact that attributes other than frequency may predominate as the basis for learning in the verbal discrimination task, especially when the dimension of concreteness is salient. In light of frequency discrimination studies (Goedel & Thomas, 1977;Wallace, Murphy, & Sawyer, 1973), however, that have shown relative frequency discrimination to be easier for homogeneous concrete pairs relative to homogeneous abstract pairs, a reluctance to accept such a resolution remains.…”