Aggression: Ethological explanations Flashcards
Adaptive functions
This explanation suggests that the main function of aggression is adaptive as aggression is beneficial to survival as a ‘defeated’ animal is rarely killed but is forced to establish territory elsewhere. Members of a species spread out in a wider area to discover resources in a different place - reduces competition pressure + possibility of starvation.
Another adaptive function - to establish dominance hierarchies. Male chimpanzees use aggression to climb their group’s social hierarchy - dominance - special status (mating rights over females).
Pettit et al - humans too - groups of young children - observed aggression being a sig. role in development of some children’s dominance over others - adaptive (naturally selected) as dominance is beneficial (power to get your own way, access to resources).
Ritualistic aggression
Ritual - series of behaviours carried out in a set order.
Lorenz - observation of animal fights of same species - little physical damage. Most aggressive encounters - mainly ritualistic signalling (showing claws + teeth, threatening facial expressions), rarely got physical. Intra-species aggressive encounters end with ritual appeasement displays - indicate acceptance of defeat + inhibit aggressive behaviour in the victor preventing any damage to loser. Wolf - expose its neck to victor deliberately making itself vulnerable to a bite.
Adaptive - if every aggressive encounter ended in death of one - threaten existence of species.
IRM + FAP
Innate releasing mechanism - built-in physiological process/structure - network of neurons in brain. Environmental stimulus (facial expression) triggers IRM which releases specific sequence of behaviours.
Fixed action pattern - the specific sequence.
Lea - FAP - 6 features
1. Stereotyped - unchanging sequences
2. Universal - same behaviour in every member of a species
3. Unaffected by learning - same for everything regardless of experience.
4. ‘Ballistic’ - once triggered, inevitable course that can’t be altered before completed.
5. Single-purpose - behaviour only occurs in a specific situation, not any other.
6. Response to identifiable specific sign stimulus.
Research into IRM + FAP
Male sticklebacks - highly territorial during spring mating season - develop red spot on underbelly. If another male enters their territory, sequence of highly-stereotyped aggressive behaviours is initiated (FAP). Sign stimulus that triggers IRM - sight of red spot.
Tinbergen - presented sticklebacks with wooden models of different shapes - regardless of shape - if red spot on it - aggressive behaviours (even attack). No red spot - no aggression even if model looked like a stickleback. Aggressive FAPs were unchanging for every encounter, once triggered FAP always ran its course to completion without any further stimulus.
AO3 - Support
Strength - Supporting research
Brunner et al - low-activity MAOA variant associated with aggressive behaviour in humans suggesting an innate basis. Evidence has also shown IRM for aggression in brain - limbic system triggering aggressive behaviour. Eth. exp. argues aggression is genetically determined + heritable, its validity is supported by evidence that shows genetic/physiological basis for aggression.
AO3 - Cultural differences
Limitation - cultural differences - evidence - aggressive behaviour more common in some human cultures than others.
Nisbett - north-south divide in US for homicide rates - more common amongst white males in south. - only true for reactive aggression triggered by arguments, he stated difference in rates was caused by a ‘culture of honour’ (response to impulsive aggression was a learned social norm) - was supported by a lab study - when white males from south were insulted in a research situation - more likely than northern males to become agg.
Difficult for eth. exp. with its view of aggression as instinctive to explain how culture perhaps plays an important role in aggression.
AO3 - Evidence against ritualistic
Limitation - Evidence against ritualistic - view that aggression evolved into a self-limiting + physically harmless ritual - challenged by observations:
Goodall - chimpanzees at Gombe Stream National Park in Tanzania - during ‘four-year war’, male chimps from 1 community set about systematically slaughtering all members of another group - co-ordinated + premeditated way - sometimes, victim held down by rival chimps as others hit + bite it in an attack lasting up to 20 mins. Violence continued despite chimps showing signals of appeasement. Signals didn’t inhibit the aggressive behaviour - goes against eth. exp.
AO3 - Unjustified generalisation
Limitation - Unjustified generalisation to humans - Lorenz didn’t study high mammals (primates) + Tinbergen didn’t study extreme destructive violence of humans. But they both made generalisations about aggressive behavior in humans, including warfare. Lorenz compared behaviour of individual animals to behaviour of entire countries/states.
Fox - war is a ‘collective undertaking that cannot be explained by any individual impulse.’
