The study was conducted by a group of evolutionary psychologists at the University of Michigan and Albright College in Pennsylvania who surveyed over 456 participants and asked them to fill up anonymous online surveys which asked questions regarding their experiences and desires with one's partner after sex.
The researchers found that those participants whose partners slept immediately after sex expressed greater desire for bonding and affection. "The more one's partner was likely to fall asleep after sex, the stronger the desire for bonding", lead researcher Daniel Kruger said.
The researchers also tried to find which sex was more likely to sleep first but found that a similar percentage of both men and women preferred sleeping soon after sex. However men were found to stay awake for longer periods when sex had not taken place.