When two Cambridge University psychology researchers started using Facebook to do personality tests, little did they know what they would unleash. Not only could Facebook be used to administer personality questionnaires, but they discovered that people's Facebook behaviour, including their "likes", could be used to predict personality. And, they claimed, computer-based personality-based judgements are more accurate than those made by humans - better even than your partner's assessment of you. Cambridge Analytica took the idea and ran with it, claiming they could micro-target voters with bespoke messages to influence them. But now, even the firm's own data expert says that the claim is overblown. Others disagree ...

Presenter/Producer: Jolyon Jenkins. Show less