Ethological explanation of aggression

Ethological explanation of aggression

1. Fixed action patterns (FAPs) are produced by a neural mechanism known as the innate releasing mechanism (IRM), and are triggered by a specific stimulus in the environment (the sign stimulus).

   • Characteristics of FAPs:
     • Stereotyped: the behaviour always occurs in the same way.
       • Universal: the behaviour is the same in all conspecifics.
         • Independent of individual experience: the behaviour is innate.
           • Ballistic: once triggered, the FAP cannot be stopped.
             • Specific triggers: each FAP has a specific trigger (sign stimulus).
   • The IRM receives input from sensory recognition circuits that are stimulated by the presence of the sign stimulus. The IRM then communicates with motor circuits to activate the FAP associated with that sign stimulus.
     • Example: Tinbergen's research with male sticklebacks. The sign stimulus is the red underbelly of another male in it's territory. Visual sensory recognition circuits recognise the red underbelly of the intruding make. The IRM is triggered and produces a FAP - an attack on the intruding male.
     • Lehman (1953) believed that Lorenz had underestimated the role of environmental factors in species-typical aggression. Environmental factors as a result of previous learning and experience interact with innate factors in complex ways.

2. The hydraulic model of instinctive behaviour (Lorenz, 1950): Each FAP has a reservoir of 'action specific energy' (ASE) that builds up over time.

   • 1) Sign stimulus is recognised by the innate-releasing mechanism (IRM)
     • 2) IRM releases action-specific energy (ASE)
       • 3) Animal performs the fixed action patter (FAP)
         • 4) Reservoir of ASE is now empty so the animal cannot repeat the aggressive behaviour until it has built up again.
           • Von Holst (1954) disagrees with the idea that a reduction in action specific energy would reduce the likelihood of aggression. He showed that performance of aggressive behaviour could itself provide a further stimulus, which would increase the likelihood of more aggressive behaviour rather than reduce it.

3. Animals and instinctive inhibition: Predator species must also have instinctive inhibitors that prevent them using their natural weapons against members of their own species. Some species have evolved weapons that make them effective hunters, eg wolves have powerful jaws and strong teeth.

   • Lorenz claimed that species such as wolves must also have instinctive inhibitors (an instinct to restrain aggressive behaviour) that prevent them using these weapons against conspecifics.
     • The argument that among predator species the killing of the same species would occur by accident is not supported by evidence on adult behaviour. In some species, the killing of conspecifics is systematic, eg male lions will will the cubs of other males. These findings challenge the ethological explanation of aggression, as they cast doubt on the claim that a lot of animal aggression is naturalistic.