ethological explanation of aggression

• The ethological explanation seeks to understand the innate behaviour of animals by studying them in their natural environments. It concentrated on aspects of behaviour that are inherited from one generation to the next. It believes aggression promotes survival by protecting resources and establishing dominance 
• The explanation suggests the main function of aggression is adaptive. It is beneficial to survival as a 'defeated' animal is rarely killed, but forced to establish territory elsewhere. This means members of a species spread out over a wider area and have to discover resources in a different place, which reduces competition pressure. Another adaptive function of aggression is to establish dominance hierarchies as this gives special status and access to resources
• Lorenz (1966) observed that fights between animals of the same species produced little physical damage. The most aggressive encounters consisted of a prolonged period of ritualistic signalling, such as displaying teeth and facial expressions of threat. He noted that intra-species aggressive confrontations end with ritual appeasement displays. These indicate acceptance of defeat and inhibit further aggressive behaviour in the victor
• innate releasing mechanisms are an inbuilt physiological process or structure which is activated by an external stimulus which in turn triggers a fixed action pattern. The environmental stimulus triggers the IRM which then releases a specific sequence of behaviours. This behavioural sequence is a fixed action pattern
• a fixed action pattern is a sequence of behaviours triggered by an innate releasing mechanism
• features of fixed action patterns:

  • stereotypes/ relatively unchanging sequences of behaviours
  • universal, as the same behaviour is found in every individual of a species
  • unaffected by learning, as they are the same for every individual regardless of experience
  • 'ballistic', as once the behaviour is triggered it follows an inevitable course and cannot be altered before it is completed
  • single-purpose as the behaviour only occurs in a specific situation
  • a response to an identifiable specific sign stimulus
• Tinbergen used male three-spined sticklebacks, which become highly territorial during the mating season. He created wooden models of fish, some resembling real male sticklebacks with red underbellies and others with different shapes and colors. Presented these models to real male sticklebacks to observe their aggressive responses. He found that regardless of shape, if the model had a red spot, the stickleback would aggressively display and attack it. If there was no red spot, there was no aggression even if the model looked realistically like a stickleback. They all responded with the same fixed action pattern of fighting behaviour. The universal nature of this behaviour suggests the fixed action pattern is innate