The Ethological Explanation Of Aggression Flashcards
Why is aggression beneficial to survive?
- Reduces competition because a defeated animal is rarely killed but instead forced into territory elsewhere, reducing competition pressure.
- Establishes dominance hierarchies. For example, a male chimpanzee’s dominance gives him special status, including mating rights over females.
Who found evidence that aggression is ritualistic?
Lorenz observed most intra-species aggression consisted mainly of ritualistic signalling (eg displaying teeth) and rarely became physical. Intra-species aggression usually ends with an appeasement display-indicates acceptance of defeat and inhibits aggression in the winner, preventing damage to the loser. This is adaptive because every aggressive encounter ending with the death of an individual could threaten existence of species.
What are innate releasing mechanisms?
An innate releasing mechanism (IRM) is a built-in physiological process or structure (e.g. A network of neurones in the brain). It acts as a ‘filter’ to identify threatening stimuli in the environment. An environmental stimulus (e.g. Facial expression) activates the IRM. It triggers or ‘releases’ a fixed action pattern (FAP).
What is a fixed action pattern (FAP)?
A FAP is a pattern of behaviours triggered by an IRM. It is argued that a FAP is a relatively unchanging behavioural sequence (ritualistic) found in every individual of a species (universal) and follows an inevitable course which cannot be altered before it is completed (ballistic).
What was the procedure of Tinbergen’s study of male sticklebacks and aggression?
Another male entering a stickleback’s territory in the mating season initiates a sequence of aggressive behaviours (a FAP) - red on the competing male’s underbelly is the stimulus that triggers the IRM that in turn leads to the aggressive FAP. Tinbergen presented male sticklebacks with a series of wooden models of different shapes.
What were the findings of the male stickleback study?
Tinbergen found that 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.
Strength: there is some supporting evidence.
Research by Brunner et al shows the low activity variant of the MAOA gene is closely associated with aggressive behaviour in humans, suggesting an innate biological basis. There is also evidence for aggression in the brain - activity in the limbic system (especially the amygdala) triggers aggressive behaviour in humans and other animals. As the ethnological explanation argues that aggression is genetically determined, its validity is supported by evidence that demonstrates the genetic and physiological basis of aggression.
Limitation: there are cultural differences in aggressive behaviour.
Nisbett et al found that when white males from the southern United States were insulted in a research situation, they were more likely than northern white males to become aggressive. This was only true for reactive aggression triggered by arguments, so Nisbett concluded the difference was caused by a culture of honour - impulsive aggression was a learned norm. It is difficult for ethological theory, with its view of aggression as instinctive, to explain how culture can override innate influences.
Limitation: there is some evidence against ritualistic aggression.
Goodall observed male chimps from one community systematically slaughter members of another group in a coordinated and premeditated fashion. This happened despite the victims offering signals of appeasement defencelessness - these did not inhibit the aggression of the attacking chimps as predicted by the ethological explanation. Goodall’s observations challenge the view of the ethological explanation that aggression has evolved into a self-limiting and relatively physically harmless ritual.
Limitation: there is evidence that some fixed action patterns are not fixed.
There are sequences of behaviours that appear to be fixed and unchanging are greatly influenced by environmental factors and learning experiences. This means that FAPs are more flexible than implied by the term ‘fixed’ (many ethnologists now prefer the term modal action pattern). The flexibility of FAPs suggests aggressive behaviours are affected by environmental influences, challenging the validity of the ethological (biological) explanation.
Limitation: there are unjustified generalisations to human aggression.
Lorenz did not study higher mammals such as primates and Tinbergen chose not to study the extreme destructive violence that is a feature of human aggression. But they both made generalisations from animal aggression to humans, including warfare. Lorenz extrapolated from the behaviour of individual animals to the behaviourof entire countries. We should be cautious about making such generalisations, especially to a complex behaviour (e.g. Warfare) which is the outcome of many interacting influences.
