Abilities are usually assumed to exist in a “positive manifold.” Experimental manipulations of physiological variables, however, suggest that negative relationships exist between certain of the neural processes contributing to simple perceptual-motor vs. perceptual-restructuring tasks. First-order correlative evidence of this phenomenon cannot be obtained because the between-individual differences in general ability level tend to exceed the behavioral effects of the intra-individual opposition between neural processes. Also, since statistical removal of the “g” variance induces bipolarity in the remaining variance, the second-order negative correlations are necessarily regarded as artifactual. A combined correlational-experimental approach is suggested to overcome this difficulty.