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Aspects of animal learning: an overview Learning: a change in behaviour as a result of experience, for example habituation, which is a simple form. Aims: o o o o o
Conditioning in insects Latent learning Insight learning Rule and concept learning Social learning
In the first half of 20th century, view was that behaviour was stereotyped and inflexible (ethology) and it was only in the second half that people realised that animals were capable of more than first thought. Best type of learning to study in the laboratory are conditioning. Learning and conditioning in insects Until 1950s, people though insects couldn't learn but certain experiments challenged preconceptions and revealed the cellular and neuronal basis of learning, in particular from studies on drosophila. The first person to conduct learning experiments on insects was Horridge (1960s) who produced the Horridge preparation which illustrates how this research began and led to understanding the cellular basis of learning. The Horridge preparation involved taking a headless cockroach, with no brain but a CNS, and suspending it over an electrified saline solution such that if the cockroach leg droops down, it receives and electric shock. The idea is that the electric shock is an aversive stimulus and the cockroach will learn to avoid the electric shock by holding its leg up. he set up two cockroaches - P is shocked with leg droops and R is a control, linked in tandem to P cockroach so it receives an electric shock when P does, even if it doesn't droop it's leg. Essentially the aversive stimulus is associated with leg-drooping in P but not R.
Test situation - animals are then connected in parallel (uncoupled) and both shocked independently. P received fewer shocks than R, as it had learned after 45 minutes of training, that drooping its leg resulted in shocking. R hadn't learnt association. Horridge concluded that ventral nerve cord and associated ganglia had mediated this effect in true Pavlovian avoidance conditioning. Avoidance conditioning easy to elicit in animals as it very adaptive behaviour. Appetitive conditioning is much more different to elicit as it requires a positive reinforcement, although it has been shown that insects can show appetitive conditioning as well. One example of this is the proboscis extension experiment, conducted on blowflies which taste with their feet. If they land on something sugary, hardwired response to extend proboscis. Neutral taste = no extension. So unconditioned stimulus of sugar, neutral stimulus of neutral taste. Soon the neutral taste became a conditioned stimulus with the proboscis extension was a conditioned response. True classical conditioning. This led to much more experimental work in the genetic and cellular basis of learning and memory. One of pioneers was Seymour Benzer - pioneered drosophilia research on common mutants. He was intereted in finding mutants for behaviours - eg deficits in circadian rhythmicity. He found mutants whose phototaxic behaviour was altered and also mutants that were particularly bad at learning and this led to the genetic dissection of the cellular basis of learning. Seymour used olfactory aversive conditioning test in which flies were trained to associate particular odours with an electric shock. The flies start off in the top of the chamber, and they fly into the choice area. What he did was pair CS+ with electric shock. CS- not paired with electric shock. Odours didn't elicit behaviours to start with. The flies learned to avoid the CS+, and retained the memory for one day with one session of training. With more training, memory retained for more than 7 days. Can use mutagenesis to produce mutant flies to screen for mutations that affect learning. The first mutation found was the dunce mutation which showed big deficit in ability to learn this olfactory task. The learned response in controls was much higher than in the dunce mutants. What the graph shows is that over time, if tests repeated, the wild type gradually forget but dunces already poor and quickly forget. Dunce mutation affects ability to lay down and retain memory. Many other mutations have also been discovered that affect different phases of learning.
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