Cognitive defeciencies or neurological dysfunction in mammals are treated with .alpha.,.alpha.-disubstituted aromatic or heteroaromatic compounds. The compounds have the formula: ##STR1## or a salt thereof wherein X and Y are taken together to form a saturated or unsaturated carbocyclic or heterocyclic first ring and the shown carbon in said ring is .alpha. to at least one additional aromatic ring or heteroaromatic ring fused to the first ring;one of Het.sup.1 is 2, 3 or 4-pyridyl or 2, 4, or 5-pyrimidinyl and the other is selected from(a) 2, 3, or 4-pyridyl,(b) 2, 4, or 5-pyrimidinyl,(c) 2-pyrazinyl,(d) 3, or 4-pyridazinyl,(e) 3, or 4-pyrazolyl,(f) 2, or 3-tetrahydrofuranyl, and(g) 3-thienyl.