Dr Stuart Semple and his international team of researchers made the discovery whilst studying Rhesus macaques in Puerto Rico. They realised that until recently, research tended to focus on communication between two individuals, without accounting for the effect of bystanders. When they did look at the bigger picture, the results were striking.

"We found that mothers' responses to the crying of their infants seems to be quite markedly affected by who's around at the time," said Semple. If those bystanders are family or subordinates, and therefore pose no risk, mothers give in to tantrums around half of the time. But if that group of bystanders contains at least one adult that poses a high risk of aggression to mothers, they will give in around 80% of the time.

Much like human babies, macaque infants have a high pitched, unpleasant cry. Although it is directed at the mother, bystanders will share the pain, says Semple, and if the crying doesn't stop, things could turn violent. Indeed, both mothers and children were more than 30 times more likely to be on the receiving end of aggressive behaviour during a crying bout than at any other time, which would explain why the infants got their own way.

And much like parents of our own species, tantrums also caused mother macaques to lose their cool. "It seems that mothers are trying to do something to end these crying bouts," said Semple, as mothers are over 400 times more likely to be aggressive to their offspring when they are crying than when they are quiet. This is something he hopes to investigate further in the future: "there is a lot more work to be done to find out exactly why mothers punish their infants, what the circumstances are, and  how that might translate to changes in infant behaviour in the long run," he adds.