FLUCTUATING asymmetry (FA) refers to the random, stress-induced deviations from perfect symmetry that develop during the growth of bilaterally symmetrical traits(1,2). Individual differences in the level of FA may influence mate choice(3) : in a number of species, females prefer to mate with males that have more symmetrical sexual ornaments(4-7). As the degree of FA has been shown to reflect the ability of individuals to cope with a wide variety of environmental stresses(2,8,9), it has been suggested that mating preferences for symmetry evolve for adaptive reasons, because the degree of FA provides honest information about male quality(10,11). Here I use simple, artificial neural networks to show that such preferences are likely to arise in the absence of any link between symmetry and quality, as a by-product of selection for mate recognition.