Ethological Explanations

• Adaptive Function of Aggression

  Lorenz - main function of aggression is adaptive, it is beneficial to survival because a 'defeated' animal is rarely killed, but forced to relocate.

  Aggression reduces competition for resources in that area, and establishes dominance hierarchies to provide special status.
• Ritualistic Aggression


  Lorenz noted that little physical damage was done during fights, with aggressive counters consisting of ritualistic signalling e.g. displaying claws and teeth.

  Confrontations often end with ritual appeasement displays, where an animal indicates defeat and inhibit aggressive behaviour in the victor.
• IRMs and FAPs


  IRM - Innate Releasing Mechanisms, an inbuilt biological stucture or process that is activated by a external stimulus that triggers a FAP.

  FAP - Fixed Action Pattern, a sequence of stereotyped pre-programmed behaviours triggered by IRMs
• Characteristics of FAPs (Lea)

  • Stereotyped - behaviour is unchanging and occur the same each time
  • Universal - same for all of a species
  • Unaffected by learning - the same for each regardless of learning
  • Ballistic - cannot be stopped once triggered
  • Single-purpose - occurs in a specific situation
  • Specific sign stimulus - only responds to one
• Key Study


  Tinbergen:

  • Presented male sticklebacks with a series of wooden models of different shapes
  • Regardless of shape, if the model had a red spot (stimulus) the stickleback displayed aggressive FAPs and attack it
  • FAPs were stereotyped, universal and ballistic
• Eval : Strength


  Kulver and Bucy found that when the amygdala of a dominant monkey was destroyed, the monkey lost it's position in the social hierarchy because of a lack of aggression. Suggests aggressive behaviour has an innate basis, adding validity.
• Eval : Weakness


  Lehrman suggested that Lorenz underestimated the role of nurture, and FAP are not simply innate and can be modified by experience. Demonstrates that the role of nurture has been ignored, affecting the validity of the explanation.
• Eval : Weakness


  Goodall observed chimpanzees at a national park and found male chimps from one group killed all the members of another group, despite the fact the victims offered signals of defeat and submission. Shows there is evidence against ritualistic aggression.