Aggression: Evaluating Evolutionary Explanations of Human Aggression

These study note follow on from: 1) Ethological Explanations of Aggression and 2) Innate Releasing Mechanisms & Fixed Action Patterns.

Tinbergen (1951) undertook an experiment with male sticklebacks. This species of fish is very territorial and aggressive. In the mating season they develop a red spot on their underside. Tinbergen observed that at this time male sticklebacks will attack another male stickleback that enters their territory. He theorised that the red spot on their underside was acting as an innate releasing mechanism and when one stickleback observed another stickleback with this red spot they would initiate the aggressive attack behaviour which is an example of a fixed action pattern. To test this out he presented male sticklebacks with a wooden model; if the wooden model had a red spot, then the male stickleback would attack. However, without the red spot the male stickleback would not react, and there was no aggression displayed.

An ethological explanation assumes that behaviour is innate; therefore, it should be uniform across all cultures. However, Nisbett (1996) found that in a laboratory experiment when South American white males were insulted they were more likely to respond aggressively than white North American males under the same conditions. This research demonstrates cultural differences that would be problematic for the ethological explanation to account for, as there was a high variation in aggressive responses.

There is evidence from the animal kingdom that aggression is not always ritualistic, Goodall (2010) studied chimpanzee behaviour for over fifty years. As part of her research, she observed groups of chimpanzees that waged a brutal war against neighbouring groups of chimpanzees, slaughtering all members of the group. Goodall (2010) referred to this type of gang behaviour as the systematic slaughtering of one group by another stronger group. This aggression is hard to explain from an ethological standpoint as the risk of injury to the attacking group is high and thus does not appear to be an adaptive behaviour.

Not all fixed action patterns are fixed. There is some evidence that learning and environmental factors can create variation within a species. Therefore, it may be more appropriate to discuss modal action patterns rather than fixed action patterns. Modal action patterns are behaviours that are instinctual such as the desire to chase in dogs (the prey drive), but that differ from one individual within the species compared to others. For example, some dogs may chase cats but some dogs do not. The differences in behaviour may be down to training, or may be down to species differentiation as a result of selective breeding of characteristics.

Exam hint: An evaluation point would be to discuss whether animal research can be extrapolated to humans. However, it is important not to dismiss animal research entirely, but just to advise that caution is required when making comparisons between animal and human behaviour.

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