Classical Conditioning

Classical Conditioning is the type of learning made famous by Pavlov's experiments with dogs. The gist of the experiment is this: Pavlov presented dogs with food, and measured their salivary response (how much they drooled). Then he began ringing a bell just before presenting the food. At first, the dogs did not begin salivating until the food was presented. After a while, however, the dogs began to salivate when the sound of the bell was presented. They learned to associate the sound of the bell with the presentation of the food. As far as their immediate physiological responses were concerned, the sound of the bell became equivalent to the presentation of the food.

Classical conditioning is used by trainers for two purposes: To condition (train) autonomic responses, such as the drooling, producing adrenaline, or reducing adrenaline (calming) without using the stimuli that would naturally create such a response; and, to create an association between a stimulus that normally would not have any effect on the animal and a stimulus that would. 

Stimuli that animals react to without training are called primary or unconditioned stimuli (US). They include food, pain, and other "hardwired" or "instinctive" stimuli. Animals do not have to learn to react to an electric shock, for example. Pavlov's dogs did not need to learn about food. 

Stimuli that animals react to only after learning about them are called secondary or conditioned stimuli (CS). These are stimuli that have been associated with a primary stimulus. In Pavlov's experiment, the sound of the bell meant nothing to the dogs at first. After its sound was associated with the presentation of food, it became a conditioned stimulus. If a warning buzzer is associated with the shock, the animals will learn to fear it. 

Terminology 

a) Unconditioned Stimulus (US) - a stimulus that evokes an unconditioned response without any prior conditioning (no learning needed for the response to occur). 

b) Unconditioned Response (UR) - an unlearned reaction/response to an unconditioned stimulus that occurs without prior conditioning. 

c) Conditioned Stimulus (CS) - a previously neutral stimulus that has, through conditioning, acquired the capacity to evoke a conditioned response. 

d) Conditioned Response (CR) - a learned reaction to a conditioned stimulus that occurs because of prior conditioning. 

e) Trial - presentation of a stimulus or pair of stimuli. 

a) Acquisition - formation of a new CR tendency. This means that when an organism learns something new, it has been "acquired". 

Basic Principles 

Pavlov believed in contiguity - temporal association between two events that occur closely together in time. The more closely in time two events occurred, the more likely they were to become associated; s time passes, association becomes less likely. 

For example, when people are house training a dog -- you notice that the dog went to the bathroom on the rug,. If the dog had the accident hours ago, it will not do any good to scold the dog because too much time has passed for the dog to associate your scolding with the accident. But, if you catch the dog right after the accident occurred, it is more likely to become associated with the accident. 

There are several different ways conditioning can occur -- order that the stimulus-response can occur: 

1. delayed conditioning (forward) - the CS is presented before the US and it (CS) stays on until the US is presented. This is generally the best, especially when the delay is short. 

example - a bell begins to ring and continues to ring until food is presented. 

2. trace conditioning - discrete event is presented, then the US occurs. Shorter the interval the better, but as you can tell, this approach is not very effective. 

example - a bell begins ringing and ends just before the food is presented. 

3. simultaneous conditioning - CS and US presented together. Not very good. 

example - the bell begins to ring at the same time the food is presented. Both begin, continue, and end at the same time. 

4. backward conditioning - US occurs before CS. 

example - the food is presented, then the bell rings. This is not really effective. 

b) Extinction - this is a gradual weakening and eventual disappearance of the CR tendency. Extinction occurs from multiple presentations of CS without the US. 

Essentially, the organism continues to be presented with the conditioned stimulus but without the unconditioned stimulus the CS loses its power to evoke the CR. For example, Pavlov's dogs stopped salivating when the dispenser sound kept occurring without the meat powder following. 

c) Spontaneous Recovery - sometimes there will be a reappearance of a response that had been extinguished. The recovery can occur after a period of non-exposure to the CS. It is called spontaneous because the response seems to reappear out of nowhere. 

d) Stimulus Generalization - a response to a specific stimulus becomes associated to other stimuli (similar stimuli) and now occurs to those other similar stimuli. 

Another Example (Jhon Watson) 

John Watson conditioned a baby (Albert) to be afraid of a white rabbit by showing Albert the rabbit and then slamming two metal pipes together behind Albert's head (nice!). The pipes produced a very loud, sudden noise that frightened Albert and made him cry. Watson did this several times (multiple trials) until Albert was afraid of the rabbit. Previously he would pet the rabbit and play with it. After conditioning, the sight of the rabbit made Albert scream -- then what Watson found was that Albert began to show similar terrified behaviors to Watson's face (just looking at Watson's face made Albert cry. What a shock!). What Watson realized was that Albert was responding to the white beard Watson had at the time. So, the fear evoked by the white, furry, rabbit, had generalized to other white, furry things, like Watson's beard. 

f) Stimulus Discrimination - learning to respond to one stimulus and not another. Thus, an organisms becomes conditioned to respond to a specific stimulus and not to other stimuli. 

For Example - a puppy may initially respond to lots of different people, but over time it learns to respond to only one or a few people's commands. 

g) Higher Order Conditioning - a CS can be used to produce a response from another neutral stimulus (can evoke CS). There are a couple of different orders or levels. Let's take a "Pavlovian Dog-like" example to look at the different orders: 

In this example, light is paired with food. The food is a US since it produces a response without any prior learning. Then, when food is paired with a neutral stimulus (light) it becomes a Conditioned Stimulus (CS) - the dog begins to respond (salivate) to the light without the presentation of the food. 

first order:

1) light -- US (food) 

\--> UR (salivation) 

2) light -- US (food) 

\--> CR (salivation) 

second order: 

3) tone -- light 

\--> CR (salivation) 

4) tone -- light 

\--> CR (salivation ) 

B. Classical Conditioning in Everyday Life 

One of the great things about conditioning is that we can see it all around us. Here are some examples of classical conditioning that you may see: 

1. Conditioned Fear & Anxiety - many phobias that people experience are the results of conditioning. 

For Example - "fear of bridges" - fear of bridges can develop from many different sources. For example, while a child rides in a car over a dilapidated bridge, his father makes jokes about the bridge collapsing and all of them falling into the river below. The father finds this funny and so decides to do it whenever they cross the bridge. Years later, the child has grown up and now is afraid to drive over any bridge. In this case, the fear of one bridge generalized to all bridges which now evoke fear. 

2. Advertising - modern advertising strategies evolved from John Watson's use of conditioning. The approach is to link an attractive US with a CS (the product being sold) so the consumer will feel positively toward the product just like they do with the US. 

US --> CS --> CR/UR 

attractive person --> car --> pleasant emotional response 

3. A Clockwork Orange - No additional information necessary! If you haven't seen this movie or read the book, do it. You will find it very interesting, and a wonderful example of conditioning in action.