Social interaction expert reveals event guest numbers should be a multiple of four

For the perfect dinner party, the best number of guests is a multiple of four. That is because four is the maximum number of people who can maintain a successful conversation, according to an expert on social interaction. The rule of four is seen in Shakespeare plays, the first Sex and the City film, with its four female best friend characters, and even the rom-com Love Actually. Professor Robin Dunbar, who highlights the conversation number limit in his recent book The Social Brain, has seen it repeatedly in groups of people, everywhere from the park to the pub, when people in these settings were studied. He says we can only keep in mind five people's mental states at once, including our own.