Films that layer many plots and relationships on top of one another, such as Love Actually, push our brains to breaking point, a new study suggests.Scientists say that ‘hyperlink films’ such as the Hugh Grant hit as well as grittier titles such as Crash and Babel that follow a number of stories in parallel throughout, require a lot of brain power to understand due to the number of emotional relationships that the viewer needs to keep track of. Hyperlink films reflect patterns that can be seen in social networks, but the number of storylines they can feature is restricted due to the limitations of the human brain.They use cinematic devices such as flashbacks, interspersing scenes out of chronological order, split screens and voiceovers to squeeze as many storylines into one film as possible, creating complex layered plots.Psycholoist Dr Jaimie Krems of Arizona State University, said: ‘Because of our evolved psychology, humans cannot break through the cognitive glass ceiling that naturally limits our ability to handle social relationships, or to understand complex interpersonal dramas.’Films such as Love Actually, Crash or Babel follow similar rules to regular social groups, according to Dr Krems and his colleague Professor Robin Dunbar of Oxford University.Existing work in the field has shown that someone can generally maintain a maximum of 150 friends and acquaintances in a regular social group, which breaks down into four or five in a ‘support group’, 12 to 15 people in a ‘sympathy group’ and 30 to 50 people in an ‘affinity group’ with the rest as acquaintances.For the study published in the journal Human Nature, the team analysed 12 hyperlink films and 10 female interest conventional films and found they all followed rules that can be seen in the real world.Dr Krems and Professor Dunbar found that an average hyperlink film contains 31.4 characters that were central to the plot, similar in size to someone’s affinity group in modern society.They also analysed works of Shakespeare which had approximately 28 characters per play, which similarly reflects a less intimate social set-up.On the other hand, ‘female interest films’ had a smaller cast of around 20 relevant characters on average - which is in the range of a conventional sympathy group and reflects female social networks in real life, according to the pair. Dr Krems believes that the hyperlink films copy reality and fail when they try to push viewers too far by involving too many characters.This shortfall in our ability to keep up with more relationships than we do in reality means that, despite virtual social networks like Facebook and Twitter giving us the tools to maintain large social groups, our brains have not evolved to handle them, they claimed.Professor Dunbar said: ‘Despite the promise it holds, digital and other new media may not help us engineer social networks or social cohesion on a larger scale, because our minds simply cannot understand or handle the mind states of more than a handful of people at once.’