ethological explanation

• Ethology is the study of how the forces of evolution have adapted the behaviour of animals
• The ethological explanation suggests aggression is adaptive to survival
• A defeated animal is rarely killed but rather is forced to establish territory elsewhere. This means that members of a species spread out over a wider area and have to discover resources in a different place, which reduces competition pressure and the possibility of starvation.
• Ethology is the study of animal behaviour in natural settings. Konrad Lorenz (1966) is the founder of ethology.
• Lorenz (1966), the founder of ethology, defined aggression as "the fighting instinct in beast and man which is directed against members of the same species"
• Two key elements of the ethological approach:

  • Aggression is an instinct. It occurs in all members of a species without the need for learning. It is innate and mostly genetically determined
  • Ethologists study aggression in nonhuman animals and extrapolate their findings to humans because we are all subject to the same forces of natural selection (Darwin, 1859)
• Ethological explanation

  An explanation that seeks to understand the innate behaviour of animals (including humans) by studying them in their natural environments.
• Innate releasing mechanism (IRM) 


  A biological structure or process (e.g. in the brain) which is activated by an external stimulus that in turn triggers a fixed action pattern.
• Fixed action pattern (FAP)


  A sequence of stereotyped preprogrammed behaviours triggered by an innate releasing mechanism.
• Another adaptive function of aggression is to establish dominance hierarchies.
• Male chimpanzees use aggression to climb their troop's social hierarchy. Dominance gives them special status (e.g. mating rights over females). This happens in humans too.
• Pettit et al. (1988) studied groups of young children and observed how aggression played an important role in the development of dominance hierarchies. This would be adaptive (and thus naturally selected) because dominance over others brings benefits such as access to resources (e.g. food and mates).
• Ritualistic aggression


  A ritual is a series of behaviours carried out in a set order. Lorenz (1966) observed that fights between animals of the same species produced little actual physical damage. Most aggressive encounters consisted of a prolonged period of ritualistic signalling (e.g. displaying claws and teeth, facial expressions of threat).
• Ritual appeasement displays indicate acceptance of defeat and inhibit further aggressive behaviour in the victor, preventing any damage to the loser.
• An example of a ritual appeasement display is at the end of an aggressive confrontation a wolf will expose its neck to the victor, a submissive appeasement gesture making itself vulnerable to a single bite to its jugular vein.
• Ritualistic aggression is adaptive because if every aggressive encounter ended with the death of one of the combatants, that could threaten the existence of the species.
• An innate releasing mechanism (IRM) is an inbuilt physiological process or structure, for instance a network of neurons (a circuit) in the brain. An environmental stimulus (such as a certain facial expression) triggers the IRM which then 'releases' a specific sequence of behaviours. This behavioural sequence is called a fixed action pattern (FAP).
• What are the six main features of FAPs according to Lea (1984)?

  Stereotyped, universal, unaffected by learning, ballistic, single-purpose, and response to a specific sign stimulus
• What does it mean for FAPs to be stereotyped?

  It means they are relatively unchanging sequences of behaviours
• Why are FAPs considered universal?

  Because the same behaviour is found in every individual of a species
• How are FAPs unaffected by learning?

  They remain the same for every individual regardless of experience
• What does it mean for FAPs to be ballistic?

  Once triggered, the behaviour follows an inevitable course and cannot be altered
• What does single-purpose mean in the context of FAPs?

  It means the behaviour only occurs in a specific situation
• What is a sign stimulus in relation to FAPs?

  It is an identifiable specific stimulus that triggers the behaviour
• What is a releaser in the context of FAPs?

  A releaser is a sign stimulus that involves communication between members of the same species
• Tinbergen's research - Procedure

  • Male sticklebacks are highly territorial during the spring mating season, when they also develop a red spot on their underbelly
  • If another male enters their territory, a sequence of highly-stereotyped aggressive behaviours is initiated (FAP)
  • The sign stimulus that triggers the innate releasing mechanism is the sight of the red spot
  • Tinbergen (1951) presented sticklebacks with a series of wooden models of different shapes
• Tinbergen's Findings

  • Regardless of shape, if the model had a red spot the male stickleback would aggressively display and even attack it
  • But if there was no red spot, there was no aggression, even if the model looked realistically like a stickleback
  • Tinbergen also found that these aggressive FAPs were unchanging from one encounter to another
  • Once triggered, the FAP always ran its course to completion without any further stimulus