According to Paul Zack that’s how many hugs will optimally release enough oxytocin in our brains to make us more empathetic and, being more empathetic, lead us to a happier life. Not only. According to Zack, empathy is the root of morality. Our capacity for empathy allows us to develop as moral beings in ways, he argues, other animals don’t. Ergo, oxytocin is the ‘moral molecule’.

Here he is explaining the theory and the evidence supporting it: