Your main task this afternoon is to interview the last two candidates for the position of manager on your team. At the close of the second interview you realise both candidates have the same relevant experience, strong academic results and practical ideas to implement once they start. You’re wondering how you’ll ever choose between them. As the final candidate gets up to leave, he catches his foot awkwardly on the table leg, upending the dregs of his coffee over the new floor. He leaves ashen-faced. Who do you think you’ll end up picking? If the pratfall effect is correct, it’ll be the clumsy candidate. The bias was discovered in 1966 by Harvard University psychologist Elliot Aronson. Along with his colleagues, Ben Willerman and Joanne Floyd, he recorded an actor answering a series of quiz questions. In one strand of the experiment, the actor – armed with the right responses – answers 92% of the questions correctly. After the quiz, the actor then pretends to spill a cup of coffee over himself (a small blunder, or pratfall). The recording was played to a large sample of students, who were then asked how likeable the contestant was. However, Aronson split the students into cells and played them different versions: one with the spillage included and one without. The students found the clumsy contestant more likeable. In Aronson’s words: The pratfall made the contestant more appealing as it increases his approachability and makes him seem less austere, more human.