ethological explanation of aggression

    Cards (11)

    • 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