Nonassociative and associative learning

Procedural memory is learning to produce a motor response to a particular input. It is separated into two categories; associative and nonassociative. Non-associative learning occurs in response to only a single type of stimulus. Two instances are habituation, in that repeated exposure to a weak stimulus results in a reduction or a loss of the response generally seen with occasional presentation of the stimulus, and sensitization that is an exaggerated response to innocuous stimuli following a strong noxious (unpleasant) stimulus.

Associative learning required the pairing of two various types of stimulus within a short time and in the right order. It enables animals to behave as if they can predict relationships of the type if A then B. Classical conditioning was first investigated in dogs which learned to related a sound with a subsequent food reward. A Hungry dog salivates at the sight or smell of food.  The food is the US (unconditioned stimulus) and the salivation an UR (unconditioned response) so called because the nervous system is hard wired in such a way which salivation occurs as an autonomic reflex response to food.  If in a series of training a sound, trials, the CS (conditioned stimulus), is presented shortly before the arrival of the food then in a subsequent test presentation of the sound alone will elicit salivation. The salivation response is now a CR (conditioned response) because the animals have learnt to salivate when the CS (sound) is presented. Classical conditioning is generalized through temporal contiguity the requirement in which the CS must be presented before the US and contingency, which animals learn that a predictive relationship exists among the US and the CS. Extinction of the conditioned response occurs if the CS is repeatedly presented without the US or if the temporal pairing of the US and CS is disrupted for example if they are presented randomly. Extinction is not the similar as forgetting.

If after extinction the pairing of CS and US is restored the CR returns much more rapidly than it does in naive animals. Classical conditioning in which the US is noxious and which results in fear responses to normally neutral stimuli is aversive conditioning.In operant (instrumental) conditioning an animal learns an association between a motor activity it performs (e.g., pressing a lever) and the arrival of a stimulus, termed the reinforcer (e.g. a food pellet). Reinforcers may be positive in that case they increase the probability which an animal will act to achieve it, or negative an aversive stimulus, like as an electric foot shock in that case the animal will work to avoid it. The Operant conditioning is used to investigate motivated behaviors.