Association (classical conditioning):
US ® UR (Food ® Salivation)
Over time, if a neutral stimulus (CR) is played with the US, it becomes associated with the US and begins to elicit the same response. Eventually, the animal learns
CS ® CR (Bell ® Salivation)
Pavlovian conditioning occurs by synapses between nerves growing together. This means that the sensory nerve carrying the message of the CS will always lead to the firing of the motor nerve, which triggers the CR.
This is very similar to classical conditioning except the animal learns by doing something i.e. it learns that an action has a certain outcome
A ® O (pushing a level ® food)
If the neutral stimulus is continuously present (not just before the US), but all the time, the animal learns to ignore the CS. The animal learns the bell signals nothing and it ignores the CS totally. This is called habituation.
If a nerve is frequently stimulated, the amount of Ca2+ that enters the pre-synaptic nerve gradually diminishes, until it is no longer enough to trigger vesicles to fuse with the pre-synaptic membrane. This means no neurotransmitter is released, which results in no post-synaptic depolarisation. The effect is, essentially, that the stimulus is ignored.
In the early 1900s, Wolfgang Kohler performed insight experiments on chimpanzees. Kohler showed that the chimpanzees sometimes used insight instead of trial-and- error responses to solve problems. When a banana was placed high out of reach, the animals discovered that they could stack boxes on top of each other to reach it. They also realized that they could use sticks to knock the banana down. In another experiment, a chimp balanced a stick on end under a bunch of bananas suspended from the ceiling, then quickly climbed the stick to obtain the entire bunch intact and unbruised (a better technique than the researchers themselves had in mind). Kohler’s experiments showed that primates can both see and use the relationships involved to reach their goals.
This type of learning is very difficult to explain using the Pavlovian model of conditioning. It is also difficult to explain using neuronal models of learning (i.e. synapses growing together through use) developed through studies on Aplysia. How insight learning occurs is unknown at the moment.