We have known ever since the Pavlov experiments that a method of learning is conditioning: when we associate something with food, we start salivating and so on (remember the Pavlov's bell and dog?). But who had thought that conditioning also works for sex? At least for quail males, making them better breeders!

Male quails placed in environments they started associating with mating sired more offspring than their untrained counterparts and this could apply to many species, humans included.

The team led by psychologist Michael Domjan at the University of Texas, Austin, checked if conditioning increases the reproductive ability and if it does, the ability would be adaptive and spread among the population.

Male quails, which breed easily in captivity, were placed in boxes with green walls or tilted floors for 5 minutes and then put in cages with a female in order to reproduce. After 5 days of repeating this, one male was put in a green or tilted box for 5 minutes and another one in an unfamiliar box.

After that both were introduced to a single female within minutes of each other. The two males mating with the same female in succession each possessed a 50% chance of fertilizing the female's eggs. But the genetic tests revealed that conditioned males had a 72% chance of being the father.

The researchers believe the male quails anticipating sex were somehow psychologically tuned on and their sperm became more competitive or sperm concentrations or the amount of semen rose.

"We tend to think of sexual behavior as instinct-driven, yet our results show that learning plays as big a role in reproduction. The results provide an evolutionary explanation for why the behaviors Pavlov observed would have been selected for." said Domjan.

"Now that we know this, what I'm really interested in is whether conditioning provides the same advantages for females," said psychologist Karen Hollis of Mount Holyoke College in South Hadley, Massachusetts.