ethological explanation of aggression

• aggression is beneficial to survival because it:

  • reduces competition as a defeated animal is rarely killed but forced into territory elsewhere, reducing competition pressure
  • it establishes dominance hierarchies. For example, a male chimpanzees dominance gives him special status

  researchers observed how aggression in children at play led to dominance hierarchies. This is adaptive because dominance over others brings benefits
• Lorenz observed most intra-species aggression consisted of ritualistic signalling and rarely caused physical damage. Intra-species aggression usually ends with an appeasement display which indicates acceptance of defeat and inhibits aggression in the winner, preventing injury to the loser. This is adaptive because every aggressive encounter ending with the death of an individual could threaten existence of species
• an IRM is an inbuilt physiological process or structure. An environmental stimulus activates the IRM and it triggers a fixed action pattern (FAP)
• Lea argues that a FAP is a relatively unchanging behavioural sequence found in every individual of a species and follows an inevitable course which cannot be altered before it is completed
• Tinbergen study on male sticklebacks and aggression procedure: he got a male to enter a sticklebacks territory in the mating season. This initiates a sequence of aggressive behaviours (FAP). Red on the competing male’s underbelly is the stimulus that triggers the IRM that in turn leads to the aggressive FAP. Researchers presented male sticklebacks with a series of wooden models of different shapes
• Tinbergen study on male sticklebacks and aggression findings and conclusions: if the model had a red underside the stickleback would aggressively display and attack it but no red underside meant no aggression. Tinbergen also found the aggressive FAP did not change from one encounter to another as once it was triggered it always ran its course to completion without any further stimulus
• One strength is that there is research support related to genetics and evolution. Genetic evidence is strong as researchers showed a link between MAOA-L gene and aggression, twin and adoption studies also suggest a genetic component. Other researchers show aggression as an adaptive behaviour and so it is genetically based. This suggests the ethological approach is correct in claiming that aggression is genetically determined heritable and adaptive
• One limitation is that same-species aggression is not always ritualistic. A researcher observed male chimps killing members of another community. The killing continued even when victims were offering appeasement signals, which did not inhibit aggressive behaviour as would be predicted by ethological theory. This challenges the ethological view that same-species aggression has evolved into a self-limiting and relatively harmless ritual
• One limitation is that Lorenz’s view of FAP is outdated. Hunt argued that FAPs are influenced by environment and learning. The sequence of behaviours in an aggressive FAP varies between individuals and situations. FAPS are not fixed but modifiable by experience so ethologists prefer the term ‘model behaviour pattern’ to reflect this flexibility. Therefore patterns of aggressive behaviour are much more flexible than Lorenz thought, especially in humans