A research to determine if there is a difference in temperature between the left and right testes is one of this year's parodic Nobel laureates.
The fertility experts Roger Mieusset and Bourras Bengoudifa measured the temperature of the testicles of French postmen, naked and dressed.
They found that the one on the left is warmer, but only when a man is wearing his clothes.
The Ig Nobel Prizes were announced at a ceremony at Harvard University.
In their research "The Thermal Asymmetry of the Human Scrotum" published in the journal Human Reproduction, the researchers explained that their experiment consisted in measuring the temperature of the scrotum with the help of probes every two minutes.
They asked 11 postal workers to stand for 90 minutes to measure the temperature of their scrotums.
In another experiment, they measured the temperature of 11 bus drivers while they were sitting.
Ig Nobels are parodic prices published in the Annals of Improbable Research, but many of the topics covered in the awards really make sense.
In this case, other research has suggested that the temperature around the testicles could affect men's fertility.
The quality of men's sperm in the western world is declining, but little is known about how to improve it. Craig Franklin told the BBC that he was devastated to learn that he had no sperm.
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