Need a hug? Take a lesson from science: The perfect cuddle is not too tight, not too soft. It’s somewhere in the middle.

Scientists at Toho University in Japan took up this cuddling question. They looked at the preferences of infants and their parents. Researchers were able to measure the preferences of the babies by using heart rate monitors for the little ones, and then pressure sensors on the hands of the adults.

In results published in the journal Cell, the study found that babies appeared to be more comforted by a medium hug. That’s compared to being held tightly or just being held with hardly any pressure at all.

The hug lasted 20 seconds. Any longer than that and researchers found the infants tended to become irritable. Babies older than 125 days appeared more relaxed with the hugs of parents compared with those from female strangers, which isn’t surprising.

This research, however, isn’t just about infants. It turns out their parents experienced more calmness as they hugged their children, too.

A hormone called oxytocin, otherwise known as the love or cuddle hormone, is released from the pituitary gland when people snuggle or bond socially. But scientists say the brief duration of the hugs in this Japanese experiment probably rule out a role by the hormone in calming the babies and their parents. Hugging a stuffed toy or petting a dog can also cause the body to release oxytocin.

Researchers acknowledge they are unsure why a short hug can cause such a calming effect.

So, hugs, it seems, are like many things in life. It’s often best to avoid too much or too little of a good thing.