Research measuring if there is a difference in temperature between the left and right testicles is one of the winners of this year's spoof Nobel prizes.
Fertility experts Roger Mieusset and Bourras Bengoudifa measured the temperature of French postmen's testicles, both naked and clothed.
They found the left one is warmer, but only when a man has his clothes on.
The Ig Nobel prizes were announced at a ceremony at Harvard University.
In their research "Thermal Asymmetry of the Human Scrotum" published in the journal Human Reproduction, the researchers explained their experiment involved measuring scrotal temperatures with probes every two minutes.
They asked 11 postal workers to stand for 90 minutes while they measured the temperature of their scrotums.
In another experiment, they measured the temperatures of 11 bus drivers while they were sitting down.
The Ig Nobels are spoof prizes that are published in the Annals of Improbable Research but many of the topics recognised in the awards actually have a serious point to them.
In this case, other research has suggested the temperature around testicles can affect men's fertility.
The quality of men's sperm in the Western world is in decline, but little is known about how to improve it. Craig Franklin told the BBC that he was devastated to find out he had no sperm at all.