Scientists have just discovered the ultimate excuse for men not engaging in "pillow talk" after sex — their brain automatically makes them fall asleep.
French researchers scanned men's brains during and after sex and found that the cerebral cortex, which is responsible for conscious thought, switches off during orgasm.
After sex, hormones including oxytocin and serotonin kick in to deactivate sexual desire, and also make men sleepy, the UK's Daily Mail reported.
Neuroscientist Serge Stoleru, who leads a group at the French medical research council Inserm, said that these experiments give the first hints about what is happening in the brain during orgasm.
"After men have an orgasm they usually experience a refractory period when they cannot be aroused," he said.
"For women it seems to be different. They don't seem to have such a strong refractory period and may be asking for more when their partners just want a rest."
The study, which was published in the journal Neuroscience and Biobehavioral Reviews, also found men's brains release a chemical called prolactin, which creates a feeling of sexual satisfaction. According to The Daily Mail, studies have shown men who are deficient in prolactin feel less tired following sex.
A University of Michigan study earlier this year found people who are still awake after their partner falls asleep post-sex often feel insecure and crave affection.
They surveyed 456 heterosexual people about their sleep patterns with their partner and found cuddling and talking after sex helps boost communication between couples.