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Preocial species

In 1937, Lorenz used young geese to demonstrate that many preocial species (where the new-born animal is able to move around) form strong bonds with the first moving objects they encounter at a specific time after hatching or birth. Lorenz called this process imprinting because it was as though the geese had formed a powerful imprint of the object as if it was their mother. Lorenz saw imprinting being genetically ‘switched-on’ and then ‘switched-off’, believing this attachment must be formed during a critical period, or it wouldn’t happen at all.

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Further studies in imprinting have shown that the critical period can be postponed or extended by changing certain environmental factors. “This has led to some researchers (e.g. Sluckin, 1965) to propose instead the existence of a sensitive period: learning is most likely to happen at this time, and will occur most easily, but it may still occur at other times” (Gross 2005, P.545). While psychologists like Gesell believed in the importance of maturation on children’s development, other psychologists emphasise the role of learning from environmental influences.

Classical conditioning is a form of learning in which we come to associate a particular response with a particular stimulus because they have been linked together several times. An example of this we can all relate to is the ‘knee-jerk’ reflex experienced when your knee is tapped in the right place. Russian physiologist Pavlov studied classical conditioning in great detail. In 1927 he conducted an experiment on the digestive process in dogs. He developed a technique for collecting dogs saliva in a tube attached to the outside of the dog’s cheek.

Pavlov noticed that the dogs would start salivating at the mere sight of the food bucket or the sound of the laboratory assistant’s footsteps that were coming to feed them. From this he predicted that, if a particular stimulus in the dog’s surroundings was present when the dog was presented with food, then this stimulus would become associated with food and cause salivation on its own. To begin with, Pavlov associated bells with giving the dogs to their food and, after doing this on several occasions, the dogs started to salivate in response to the bell. The reflex of salivation had become conditioned. The stimulus (the bell) became a conditioned stimulus as a result of regular association with the unconditioned stimulus (the food).

In 1924, Watson, an extreme behaviourist, argued that if he were given ‘a dozen healthy infants…and my own specified world to bring them up in, and I’ll guarantee to take any one at random and train him to become any type of specialist I might select – doctor, lawyer…and yes, even beggarman and thief, regardless of his talents, penchants, tendencies, abilities, vocations, and race of his ancestors’ (Hayes and Orrell 1998, P.2).

Watson was the first psychologist to apply the principles of classical conditioning to human behaviour, he set-up an experiment using an 11 month old baby, where he associated the sight of a white rat with the sound of a hammer striking a steel bar just out of sight behind the baby’s head. As you can imagine Watson was successful in inducing a phobia of rats in the young boy. This is considered to be one of the most ethically dubious psychology experiments ever conducted. Operant conditioning is where a response is learnt not simply because it’s associated with a particular stimulus, but because it produces pleasant consequences. It deals with voluntary actions rather than just reflexes. In 1911 Thorndike named this the Law of Effect.

Skinner was the psychologist most responsible for developing this theory. He created the Skinner box, which contained a light, a lever and a food delivery chute. In the box he would place a rat or pigeon and when they stood on the lever a pellet of food would be delivered, effectively rewarding the animal for its actions and positively reinforcing the behaviour so it was more likely to happen again. In the same way, rats who had to press the lever to avoid an electric shock, still had pleasant consequences, but through negative reinforcement.

Behaviour which has been learned through negative reinforcement does not die out quickly, even when it is no longer being reinforced. Behaviour which has been learned through positive reinforcement is not so resistant. How quickly it dies out depends on which of the four main kinds of reinforcement schedule were being used when the behaviour was being learned, though a psychologist may use a combination of them when studying a specific form of learning.

The four main reinforcement schedules are: Fixed-ratio reinforcement, where the animal receives reinforcement according to how many correct responses they have made and so the more responses the higher the reward, but this way of learning is not very resistant to extinction; Variable-ratio reinforcement, where the animal is reinforced according to the number of correct responses they have made, but the required number is subject to change, this way of learning is more resistant to extinction than Fixed-ratio; Fixed-interval reinforcement, where a certain period of time needs to pass between reinforcements, this way of learning is also not very resistant to extinction; and Variable-interval reinforcement, where the time which has to pass between reinforcements changes each time, an animal trained according to this schedule produces a steady response rate which is highly resistant to extinction.

When presented with this evidence it is, I think, impossible to side completely with either the nativists or the behaviourists. That is where the interactionists come in, they believe that nativism and behaviourism aren’t mutually exclusive. Both Freud and Piaget were interactionists, they believed that the environment must not only be benign, that is not harmful in any way, but particular environmental input is often necessary for a characteristic or ability to develop. They believe experience is as important as maturation. A good example of this is language, we all possess the skills to learn any language, but tend to learn the language of the community in which we grow up.

In 1953 Tinbergen, an interactionist, conducted a study of sticklebacks. He showed that a sign stimulus in the environment, the flash of red on another male’s belly, triggered their attack ritual – an inherited behaviour, triggered by an environmental stimulus. Hebb’s (1949) example of the link between genetic influences and the environment was that of a developing egg – without the genetic component there is no egg, but without the supporting environment, the warmth, the egg dies. There are several areas of behaviour where the nature-nurture debate is particularly predominant, I will now look at a couple of these controversies.

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