Asked by: Alan Hughes-Hallett, Wanstrow
There's no known limit! If you ask a mnemonist or memory savant to learn a list of names they may remember thousands, tens of thousands or even hundreds of thousands with no trouble, just as they can learn lists of thousands of digits. Some people, who have a neurological condition called ‘hyperthymesia’, remember everything that happens to them every day, including the name of every person they have ever met.
The rest of us evolved to cope with no more than about 150 social relationships. This is known as Dunbar’s number after the anthropologist Robin Dunbar. He discovered that groups of hunter-gatherers, units in armies, divisions in businesses and many other groups tend towards a limit of 150. And it seems that social media do not change our basic nature. Even people who have thousands of 'friends' on Facebook rarely maintain more than 150 meaningful relationships.