Chimpanzees under attack exaggerate their screams to get help from higher ranking group members, researchers from Fife have discovered.
The study found primates produce high-pitched and prolonged screams when they were the victims of severe aggression such as beating.
Their cries were exaggerated if there was another higher-ranking chimp in the area who could challenge the aggressor.
St Andrews University experts spent nine months in Budongo Forest, Uganda.
They recorded the apes' screams during attacks by chimps and carried out a computerised analysis of the acoustics.
Dr Katie Slocombe from the university's School of Psychology, who led the study, said: "We conclude victims use screams flexibly to recruit help from others and have a complex understanding of third party relations.
"They know exactly who can challenge who, and this knowledge of social relationships influences their vocal production.
"If no-one is there to help them then the screams are normal but if someone is about then they make it sound even worse than it is.
"This shows there is more flexibility in their vocal communication than previously thought."
Dr Slocombe said they were still researching the underlying reasons for the exaggerated screams.
"It could be that they are wanting to falsely deceive the higher ranking chimpanzee into thinking it is really bad," she said.
Dr Slocombe said that while direct parallels could not be drawn between the actions of the chimps and human behaviour, they displayed similar characteristics.
She said children often did not cry when they hurt themselves while on their own, but started crying if someone else was there.
The research was funded by the Biotechnology and Biological Sciences Research Council.
It is part of a wider study into the behaviour of chimpanzees.
The findings are published in the Proceedings of the National Academy of Sciences.