Ethological explanation for aggression Flashcards
What does the ethological explanation seek to undertsand?
- seeks to understand the innate behaviour of animals by studying them in their natural environments
What are the two key elements of the ethological approach?
- aggression is an instinct
- is innate and mostly genetically determined
What does the ethological approach suggests the main function of aggression is?
- adaptive
What is the first adaptive function of aggression?
1) reduces competition pressure & possibility of starvation
- a defeated animal is rarely killed but forced to establish territory elsewhere > beneficial to survival
- means that members of a species spread out over a wider area & have to discover resources in a different place
What is the second adaptive function of aggression?
2) helps to establish dominance hierarchies
- male chimpanzees use aggression to climb their troop’s social hierarchy> dominance gives them special status (e.g. mating rights over females)
Explain study that found dominance hierarchies in humans
- Pettit et al
- studied groups of young children & observed how aggression played an important role in development of DH
= adaptive > dominance over others brings benefits such as first access to resources
What is an example of aggression that is adaptive?
- ritualistic aggression
What is a ritual?
- series of behaviours carried out in a set order
What did Lorenz observe?
- that fights between animals of the same species produced little actual physical damage
- but aggressive encounters consisted of a prolonged period of ritualistic signalling
e.g. displaying claws, teeth
What did Lorenz argue aggressive confrontations end with?
- ritual appeasement displays
- these indicate acceptance of defeat & inhibit any further aggressive behaviour in the victor, preventing any damage to the loser
e.g. wolf will expose its neck to the victor
How is ritualistic aggression adaptive?
- enables members of species to compete & establish dominance without actually harming each other as this would threaten existence of species
What are the examples of innate aggression?
IRMs and FAPs
What is an innate releasing mechanism (IRM)?
- A inbuilt biological structure or process
- an environmental stimulus triggers the IRM which then releases a specific sequence of behaviours (FAPs)
What is a fixed action pattern (FAPs)?
- a sequence of stereotyped programmed behaviours triggered by an IRM
What are the six main features of FAPs according to Lea?
- Stereotyped, relatively unchanging sequence of behaviours
- Universal, same behaviour found in every individual of a species
- Unaffected by learning, same for every individual regardless of experience
- Ballistic, once behaviour triggered cannot be altered until behaviour is complete
- single-purpose, only occurs in a specific situation, no other
- response to specific sign stimulus
What does Tinbergens research demonstrate?
- How FAPs in sticklebacks are universal
What are sticklebacks like during the mating season?
- are highly territorial, build nests where females lay eggs
- also develop red bellies during this time
- If another male enters their territory, the stickleback will attack > FAPs are initiated
- sign stimulus that triggers IRM is the sight of red spot
What was Tinbergen’s research procedure?
- Male sticklebacks were presented with a series of wooden models of different shapes
What was Tinbergen’s research findings?
- regardless of the shape, if the model had a red spot the male stickleback would attack it
- All responded with the same FAP of fighting behaviour (universal>innate)
- FAP always ran its course to completion once triggered
What is a strength of the ethological explanation?
- support from research related to genetics
- e.g. Brunner et al’s study>MAOA-L gene is closely associated with aggressive behaviours in humans
- Twin & adoption studies> significant genetic component to aggression in humans
- point to innate basis to aggressive behaviour
- E approach correct in claiming aggression is genetically determined, adaptive & heritable
What is a counter point for research supporting genetic basis?
- aggressive behaviours differ from one culture to another
- Nisbett> one type of homicide was more common in white men in the Southern US than in the northern US
- concluded that difference was caused by a ‘culture of honour’ in the southern US> less prevalent in North
- aggressive behaviour comes from learned social norms rather than innate
- culture can override innate predispositions
What conflicting research is there for ritualistic aggression?
- aggression against members of the same species is not ritualistic
- Goodall observed a ‘four year war’ in which male chimps from one community killed all the members of another group
- did this is a systematic way
- victim held down by rival chimps while others hit it in an attack lasting many minutes
- violence continued even when victims offered appeasement signals (did not inhibit aggression)
- challenges E approach that aggression is a harmless ritual in same species
What is a limitation of fixed action patterns?
- Lorenz’s original view of FAPs is outdated > saw them as innate & unchanging
- Hunt> FAPs are actually greatly influenced by environmental factors & learning experiences
- e.g. duration of each behaviour in a sequence varies from one individual to another
- Modifiable by experience, so ethologists prefer the term ‘Modal behaviour pattern’ to reflect this
- patterns of aggressive behaviour much more flexible
