Sexual attraction: In species which reproduce sexually, sexual attraction is attraction to other members of the same species for reproduction. This type of attraction is a very important survival factor. Sexual attraction in animals Sexual attractiveness in non-human animals depends on a wide variety of factors. Often, there is some element of the animal's body which is adapted to be sexually attractive to the opposite sex: the bright plumage and crests of some species of birds, for example. In many species, there are behaviors which appear to be adapted for sexual display. Some of these attributes seem to be adapted to demonstrate fitness and health, for example by demonstrating the ability to sustain an "expensive" feature with no other apparent survival function. The adaptation takes place in the displaying gender in parallel to the development of the prefenece in the other gender. It is possible for the adaptation to be so expensive in terms of fitness that it causes major survival problems (see game theory), especially where, as in moose, a direct competitive element is involved. Frequently (especially in insects) chemical signals are used to generate sexual interest and to locate potential mates. These signals, known as pheromones, can produce a profound effect upon an animal's behaviour even when present in very minute quantities. Common elements of sexual attraction in humans Typically, sexual attraction refers to a person being drawn to another in order to have a sexual relationship. Sexual attractiveness of a person to another person depends on both persons; to some extent there is universal agreement as to what is sexually attractive among a species, but individuals have subjective opinions as well. Much of human sexual attractiveness is governed by physical attractiveness. This involves the senses, in the beginning especially: visual perception (how the other looks) audition (how the other sounds, mainly the voice; what may also vary widely is how noisily somebody walks (also depending on the footwear), but this is not necessarily a big factor for sexual attraction, either way) olfaction (how the other smells, naturally or artificially; the wrong smell may be repulsive). (disputed — see talk page) Some studies suggest that the source of the physical attraction of a human male to a human female is dependent upon a proportion between the width of the hips and the width of the waist (see Golden ratio). As with animals, pheromones may also enter into the picture, though less significantly than in the case of animals. Theoretically, the "wrong" pheromone smell may cause someone to be disliked, even when they would otherwise appear attractive. Frequently a pleasant smelling perfume is used to encourage the member of the opposite sex to more deeply inhale the air surrounding its wearer, increasing the probability that the pheromones from the individual will also be inhaled.
