The role of neural mechanisms
- The lateral hypothalamus: Investigations into the role of the hypothalamus in eating behaviour began in the 1950's when researchers discovered that damage to the lateral hypothalamus (LH) in rats caused a condition called aphagia. Researchers also found that the stimulation of the LH elicits feeding behaviour. These opposing effects of injury and stimulation led researchers to conclude that they had discovered the 'on switch' for eating behaviour. Researchers found that the neurotransmitter neuropeptide Y was particularly important in turning on eating and when Wickens (2000) injected this neurotransmitter into the hypothalamus of rats, they found that it caused them to immediatley begin feedings. Further on to this, Stanley et al. (1986) found that repeated injections caused the rats to become obese in just a few days. This seems to suggest that the role o neural mechanisms is imporant in controlling eating behaviour.
- However, the role of the lateral hypothalamus- the view that the LH served as an 'on switch' for eating behaviour turned out to have a few problems, for example, if there was damage to the LH then deficits were caused in other aspects of behaviour (e.g thirst and sex rather than just hunger, and also, more recent research has shown that eatihng behaviour is controlled by neural circuit that run through the brain, not just by the hypothalamus and so the validity of the theory can be questionned.
- It is also deterministic as it fails to mention how things such as psychological disorders can affect the amount of food that we eat. It only takes into account the biological theories of eating behaviour and so the validity of the theory can again be questioned.
- They have also found that the role of neuropeptide Y has doubt as to whether its normal function is to infleunce feeding behaviour,. Marie et al. (2005) geneticall manipulated mice so that they did not make NPY. They found no subsequent decrease in their feeding behaviour. The researchers suggested that the hunger stimulated by injections of NPY may actually be an experimental artefact, in that the flood of NPY during experimental maniopulations could have caused behaviour not like that caused by normal amounts of the neurotransmitter.
Evolution of food preferences
- There are many explanations that make up the evolutionary explanation. One of these explanations is 'taste aversion'. This is also known as bait shyness and was first discovered by farmers trying to rid themselves of rats. They found that it was difficult to kill the rats by using posioned bait because rats would only take a small amount of any nrw food, and it they became ill, the would rapidly learn to avoid it. For this reason, taste aversion was orginally known as 'bait shyness'.
- Garcia et al. (1995) were the first to study taste aversion in the laboratory and found that rats who had been made ill through radiation shortly after eating saccharin, developed an aversion to it and very quickly associated their illness with the saccharin.