As they report in the Proceedings of the National Academy of Sciences, they videotaped the animals' behaviour for several hundred hours over the course of 16 months in order to record three things: facial and vocal expressions, hand and foot gestures, and the behavioural context in which these expressions and gestures took place (eg, grooming, play, sex and aggression).

ECONOMIST: Evidence that the first words were movements, not sounds

Andrew Lo, of MIT's Sloan School of Management, was fond of pointing out that in the physical sciences three laws can explain 99% of behaviour, whereas in finance 99 laws can explain at best 3% of behaviour.

ECONOMIST: Schumpeter