Inventory data on a large sample of middle-aged twins and their spouses confirmed that spousal pairs are consistently but weakly similar on traits of personality, interests, talents, and attitudes. We argue, however, that neither the Similarity model of mate selection, nor one of its facets, the Equity model, can account for specific mate choice. We therefore tested the hypothesis that people select their mates using idiosyncratic criteria and that the spouses of monozygotic (MZ) twins should therefore be very similar. When compared to spouses of dizygotic (DZ) twins or even to random pairs of spouses, the spouses of MZ twins failed to show the predicted excess of small intra-spouse differences. We asked 547 of these twins to rate their attitudes toward their cotwin's choices of wardrobe, furnishings, vacations, jobs - and spouses; a similar questionnaire was completed by the spouses of these twins. Both data sets confirm that MZ twins are very similar in most of their choices, more so than DZ twins, but nearly 40% of both MZs and DZs recall that they actually disliked their cotwin's choice of mate at the time that choice was made. Similarly, 30% of the spouses of MZ twins report actually disliking the identical twin of the mate they had recently selected. Our findings suggest that characteristics both of the chooser and the chosen constrain mate selection only weakly. We propose that it is romantic infatuation that commonly determines the final choice from a broad field of potential eligibles and that this phenomenon is inherently random, in the same sense as is imprinting in precocial birds
