Many animal species are known to give off chemical signals to attract sexual partners, but scientists still debate whether pheromones used in aphrodisiac perfumes actually play any role in human mating.

On Wednesday, Australian researchers added fuel to the fire by stating that two naturally occurring steroids widely thought to be appeal-boosting human pheromones have no impact on "mate perception".

The chemicals -- estratetraenol (EST) or androstadienone (AND) -- are already a component of perfumes that promise to leave the opposite sex weak at the knees.

But the titillating effect may be all in the mind, researchers wrote in the journal Royal Society Open Science.

"AND and EST are unlikely to be human pheromones," said a research quartet from the University of Western Australia.

They tested whether those chemicals -- the lead contenders for human pheromone status -- had any effect on 94 heterosexual men and women in two lab experiments.

In the first stage, participants were asked to indicate whether a "gender neutral" face, created by computer-fusing photos of people from both sexes, belonged to a man or a woman.

In the second, they had to rate faces for attractiveness, and whether they thought the person had an adulterous nature or not -- part of what makes up "mate perception".

Being exposed to either AND or EST during the experiments made no difference to the participants' choices as they would have done if they truly were pheromones, the researchers found.

In previous research, men and women reported that a person's scent affected their sexual interest, and women often say they place more importance on a man's smell than his looks.

Yet no human sex pheromones have been identified with any certainty, and previous studies on AND and EST's aphrodisiac effects have yielded contradictory findings.

Despite a lack of scientific proof, AND is marketed as a male pheromone, and EST a female one -- often in pricey perfumes.

"We recommend a return to first principles in the search for human pheromones," said the team -- referring to the fundamental assumptions on which any theory is based.

They called for trials run by scientists rather than perfume labs in the quest for actual human pheromones.

Source: AFP