R relationships to new stimuli. Ultimately, all Pavlovian Conditioning has at its heart in-born, or unconditional, reflexes that exist because of their basic survival value.
All animals, including humans, are born with a limited set of reflexes--genetically wired-in responses to specific environmental stimuli. A reflex is a relationship between a specific environmental event (a stimulus, or S) and a fixed behavioral action (a response, or R) that it evokes. Reflexes have enormous survival value. Those things that any organism doesn't have the time or the neural capacity to learn but needs to be able to do to survive and reproduce, is going to be encoded into it's inheritance if it is to have a chance at survival. Those individuals who either have the best genetic endowment for reflexes, or who have the capacity to modify their genetically predetermined reflexes, have a better chance of survival and reproduction.
The modification and extension to new situations of genetically determined reflexes underlies the survival value of Pavlovian conditioning.
Pavlovian conditioning is the fundamental building block of learning. It is so basic to how animals adapt to their environment that it is shown by virtually all animals, from simple multicellular organisms such as flatworms (Planaria) to humans. There is even evidence that single-celled animals such as Paramecia are capable of Pavlovian conditioning.
Pavlovian conditioning is all about the fact that we learn to associate these pre-existing SR relationships to new stimuli. Ultimately, all Pavlovian Conditioning has at its heart in-born, or unconditional, reflexes that exist because of their basic survival value.
The enormity of the importance of these pre-wired behaviors, and our limited capacity for modifying them, will become a major topic of our discussion by the end of the semester. But let's not get ahead of ourselves just yet. Just what are the characteristics of these inborn reflexes?
The term unconditional is instructive. The relationship exists unconditionally--the first time, and every time, the stimulus is presented, the response reliably follows. It is in the nature of the organism to behave this way. Pavlovian Conditioning is said to occur when a previously neutral stimulus, such as a tone or light that normally is of little interest to the organism, becomes associated with an already existing reflex to the extent that it will, by itself, evoke a response. This new reflex is said to be conditional, in that its ability to evoke a response depends upon the stimulus having been associated with a previously existing reflex.
How does conditioned behavior come about? To begin our discussion, let's look at an example--Pavlov's original experiment.
The experimenters first performed a minor operation on a dog to relocate its salivary duct to the outside of its cheek, so that drops of saliva could be more easily measured. The dog, which was food deprived, was then harnessed in an apparatus (see diagram above) to keep it steady. Periodically, a tone was sounded, followed shortly thereafter by meat powder being placed in the hungry dog's mouth (each pairing of tone/meat powder is referred to as a trial). Meat powder causes a hungry dog to salivate, whereas tones have little effect. The dog's salivation to meat powder is an unconditional reflex--it is in-born, in that dogs do not have to learn to salivate when food is placed in their mouths. Initially, the dog shows little responsiveness to the tone. Over time, however, the dog comes to salivate at the sounding of the tone alone. When this occurs, Pavlovian conditioning has occurred, in that a new, or conditional, reflex has developed.
In describing the process by which a new reflex develops, Pavlov coined a number of terms that are still the basic terminology of conditioning:
| Unconditional Reflex | UCS |  | UCR |
| food | salivation | ||
| Conditional Reflex | CS | | CR |
| tone | salivation |
For a cheap-thrill, see the first animated .gif file I ever made, a crude representation of the temporal relationship between the CS and the CR in a dog which has already been Pavlovianly conditioned. There's an interesting story about why I made this if you click it on.
Typical results from a Pavlovian experiment are diagrammed below:
Every tenth trial is a test to see the extent to which tome alone is followed by salivation. The CS would be presented by itself for 30 seconds, and the amount of salivation is recorded. This development of the CR is shown in the "Acquisition" phase of the diagram. Following acquisition, the CS is presented over and over again, without being paired with the UCS. The resulting diminishing of the CR is demonstrated in the "Extinction" phase of the diagram. On subsequent days, the dog is brought back into the lab, harnessed, and the CS is again presented repeatedly without the UCS. At first, there is a recovery of responding at the start of the session, even though the CS and UCS have not be re-paired. Pavlov referred to this as spontaneous recovery. Eventually, the dog would not respond to the CS, even at the start of a new session.
 | Before reading any further, click on Blinky and do the demonstration of Pavlovian conditioning. |
In this demonstration of the dentist's drill:
| Unconditional Reflex | UCS | | UCR |
| drilling | pain | ||
| Conditional Reflex | CS | | CR |
| sound of drill | pain |
Look at how you diagrammed this example, and how I did. If there are places where we differed, can you see why? It might be a simple matter of what we called things. Take a minute to reflect on your analysis and mine, and be sure that you can reconcile any differences. When you can, it's time to move on.
One of the common misconceptions about a scientific analysis of behavior is that it doesn't explain emotions. the discussion above should indicate that this isn't so.
Higher-order conditioning. Not all Pavlovian conditioning involves the presence of an inborn reflex. Much of our conditioning occurs when a new stimulus is paired with an existing conditional reflex, thereby producing another reflex. When an existing conditional reflex acts as the basis for yet another reflex, higher-order conditioning is said to occur. For example, in our dentist drill demonstration, you may feel uncomfortable next time you see the computer where you were working when you heard the drill. You may particularly focus on the headphones that you were wearing when the drilling sound started. That would be Higher Order conditioning, since the computer/headphones and actual drillingpain have never been associated, only the conditioned stimulus of the sound of drilling and the computer/headphones.
Before going on, be sure to Make Up Your Own Question!
| Go to: | ||
| UGLI 2 | Principles of Learning and Behavior | |
| Spawn UGLI 2 in Word | Tom Creed | CSB/SJU page |
