Robin Dunbar, an anthropologist, studied animals to see if their brain size affected how many stable relationships they could form.
He came up with a formula that calculates the limit of relationships for different groups.
So what's the number for humans? 150
You may have 1,000 friends on Facebook and 500 followers on Instagram. 150 may seem too low.
The people included in the 150 are strong, stable connection - most likely everyone knows each other.
Some say the strong ties are important, it is the weak ties where no one necessarily knows the other person, that are important.
Social Media helps us strengthen these weak ties.