While observational methods are more commonly used by ethologists and biologists to explain evolutionary behaviour. The aggression of this fish has been studied by ethologists and comparative psychologists. Ethologists have made much more use of such cross-species comparisons than comparative psychologists have. Ethologists can classify imitation in animals by the learning of certain behaviors from conspecifics. Most ethologists believe that aggression confers biological advantages. Other important influences were ethologists Nikolaas Tinbergen and Robert Hinde. Ethologists have long documented the exchanges of sex to promote group cohesion in social animals. Most contemporary ethologists view the elephant as one of the world's most intelligent animals.