ethological explanation of aggression

• Adaptive

  • Aggression is beneficial to survival because it:
  • Reduces competition as a defeated animal is rarely killed but forced into territory elsewhere, reducing competition pressure
  • Establishes dominance hierarchies. A male chimpanzee's dominance gives him special status (e.g. mating rights)
  • Pettit et al (1988) observed how aggression in children at play led to dominance hierarchies - this is adaptive (therefore naturally selected) because dominance over others bring benefits
• Ritualistic - a series of behaviors carried out in a set order

  • Lorenz (1966) observed most intra-species aggression consisted of ritualistic signalling (e.g. displaying teeth) and rarely caused physical damage
  • Intra-species aggression usually ends with an appeasement display - 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
• IRM - triggered by an environmental stimulus

  • An innnate releasing mechanism (IRM) is an inbuilt physiological process or structure (e.g. a network of neurons in the brain)
  • An environmental stimulus (e.g. facial expression) activates the IRM. It triggers or 'releases' a fixed action pattern (FAP)
• FAP - universal and ballistic

  • A fixed action pattern (FAP) is a pattern of behaviors triggered by an IRM
  • Lea (1984) argues that a FAP is a relatively unchanging behavioral sequence (ritualistic) found in every individual of a species (universal) and follows an inevitable course which cannot be altered before it is completed (ballistic)
• Tinbergen (1951) Male stickleback and aggression: Procedure

  • Another male entering a stickleback's territory in the mating season initiates a sequence of aggressive behaviors (a FAP) - red on the competing male's underbelly is the stimulus thaat triggers the IRM that in turn leads to the aggressive FAP
  • Tinbergen (1951) presented male sticklebacks with a series of wooden models of different shapes
• Tinbergen (1951) Male stickleback and aggression: Findings and conclusions

  • If the model had a red underside the stickleback would aggressively display and attack it - but no red meant no aggression
  • Tinbergen also found the aggressive FAP did not change from one encounter to another - once triggered it always ran its course to completion without any further stimulus
• One strength is support from research related to genetics and evolution

  • Genetic evidence is strong e.g. Brunnner et al (1993) showed a link between MAOA-L gene and aggression, twin and adoption studies also suggest a genetic component
  • Research by Wilson and Daly (1996) shows aggression as an adaptive behavior and therefore genetically-based
  • This suggests the ethological approach is correct in claiming that aggression is genetically determined heritable and adaptive behavior
• Counterpoint for support from research related to genetics and evolution

  • Nisbett (1993) found homicides based on reactive aggression (responding to threat) were more common in the southern US than in the north - 'culture of honor' less prevalent in the north
  • Therefore culture can override innate influences, which is hard for ethological theory to explain
• One limitation is that same-species aggression is not always just ritualistic

  • Goodall (2010) observed male chimps killing members of another community - the aggression was systematic
  • The killing continued even when victims were offering appeasement signals, which did not inhibit aggressive behavior 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
• Another limitation is that Lorenz's view of FAPs is outdated

  • Hunt (1973) argued that FAPs are influenced by environment and learning. The sequence of behaviors in an aggressive FAP varies between individuals and situations
  • FAPs are not fixed but modifiable by experience, so ethologists prefer the term 'modal behavior pattern' to reflect this flexibility
  • Therefore patterns of aggressive behavior are much more flexible than Lorenz thought, especially in humans
• Evaluation extra: Born to be aggressive?

  • Ethologists argue aggression is an innate instinct, which implies that humans are inevitably aggressive and will fight each other (e.g. wars), FAPs show this
  • However, other approaches (e.g. cognitive) suggest aggression is not inevitable, is under rational control and more affected by learning and social norms
  • Therefore aggression may have instinctive elements but in humans it is more strongly influenced by cognitive and social factors