Project 1: Chapter 3: Exercises 1,2,3

Basic Phenomena of Classical Conditioning: Acquisition, Extinction, Spontaneous Recovery

This exercise is based on the materials in the Sniffy Pro manual.  To get a feel for the software download the Sniffy Demo software available on this site, and print off this document to follow step by step.  Some users may find it helpful to run the Overview Tutorial, before they try Project 1.

Putting Everything Together To Understand Classical Conditioning

Acquisition, extinction, and spontaneous recovery in classical conditioning are analogous to the phenomena with the same names in operant conditioning. Acquisition is produced by pairing the Conditioned Stimulus (a CS like a Tone) and an Unconditioned Stimulus (a US like a shock) over a number of trials, with the result that the CS acquires the capacity to elicit a new Conditioned Response (CR) that resembles the Unconditioned Response (UR).

In Sniffy Pro experiments, the Light, Tone, and Bell can be used as CSs.  The US is mild shock of varying levels. There are two ways to measure the effect on Sniffyâs behaviour.  Suppression Ratio window contains the classical-conditioning response measure that psychologists typically employ in CER experiments.  In this exercise we will concentrate on the second measure of conditioning, measuring Sniffyâs overall movement under normal, training, and test conditions.

During a classical-conditioning experiment, you can observe four things; the occurrences of the CS and US (in the Cumulative Record Window), changes in Sniffy's psychological states (the CS Response Strength mind window), Sniffy's responses to the CS and US during and after their presentation (Suppresion Ratio, or Motion Ratio in two types of conditioning methods). The Cumulative Record contains raw data about Sniffy's behavior throughout the experiment, shows when the different stimuli occur, and enables you to view the ways in which the stimuli affect Sniffy's bar pressing.

We are going through three stages in these three exercises.  Acquisition (learning) of a classically conditioned response is produced by repeatedly presenting the CS followed by the US. As a result of this acquisition procedure, the CS gradually acquires the capacity to elicit a new response (CR) that in most forms of classical conditioning resembles the UR. Once a classically conditioned response has been acquired, it can be eliminated by repeatedly presenting the CS alone÷that is, without the US. Elimination of a CR by repeatedly presenting the CS without the US is called extinction. If the animal is removed from the experimental situation for a day or so after a CR has been extinguished and then returned to the experimental setting and given a second extinction session, it is likely that CR will occur again during the first few trials of the second extinction session. This reappearance of a previously extinguished CR is called spontaneous recovery.  Early in the second extinction session, the CR is stronger than it was at the end of the first extinction session but weaker than it was at the end of acquisition.

Stage 1: Exercise 1: Basic Acquisition of a CR

Acquisition is produced by setting up a series of trials in which a CS regularly precedes occurrences of the US. The steps outlined below describe how to set up and run an experiment in which Sniffy receives 10 pairings of the medium-intensity tone CS with the medium-intensity shock US.

• We plan to use the movement ratio as the measure of classical conditioning, so simply start the Sniffy Pro program or, if the program is already running, choose the New command from the File menu.
• Use the Save As command in the File menu to save the file under an appropriate new name (for example, Ex1-ClassAcq) on your computerâs hard drive.
• Select an appropriate destination for the file on your computerâs hard disk. If you are running the Macintosh version of the program, the Sniffy Files folder that we asked you to create on your hard drive when you installed the program is the best place to keep all your Sniffy files. If you are running the Windows version of the program, we suggest that you save this exercise and all future exercises in the Sniffy Pro for Windows folder that the installer program created. That folder is inside the Program Files folder at the root level of your hard drive.
• Choose the Design Classical Conditioning Experiment command from the Experiment menu. In the Classical Conditioning Experimental Design dialogue box, make the following settings:
  • In the Stage section, be sure the numeral 5 appears in the text box located to the right of Interval Between Trials, indicating that the average interval between trials will be 5 minutes.
  • In the text box located to the right of Present Each Trial Type, type 10.
  • In the First Stimulus panel of the dialogue box, check that the medium-intensity tone is selected. Make sure that no other first stimulus is selected.
  • In the Second Stimulus panel of the dialogue box, make sure that the medium-intensity shock US is selected.
  • Carefully check to see that all the settings are correct.
  • Click the Save command button.
• After the Experimental Design Dialogue box has closed, choose the Run Classical Conditioning Experiment command from the Experiment menu.
• If you want to speed up execution of the experiment, select the Isolate Sniffy (Accelerate Time) command from the Experiment menu. However, if you use this feature, be careful not to let the program run very long after the experiment is completed. You will need the file that this exercise creates in several future exercises. Thus you want to avoid inadvertently recording unneeded data about Sniffyâs activities once the classical conditioning experiment is finished. Remember that the program beeps at the end of a classical conditioning experiment.
• After the last acquisition trial, save your results by selecting the Save command from the File menu.

During the next 50 min of program time, the program will automatically run the experiment. While the program is running, the Movement Ratio window will draw a bar graph that shows Sniffyâs movement ratio as a function of trials. At the same time, the CS Response Strength mind window will produce a line graph depicting changes in the CSâs capacity to elicit a CR.

At the end of the experiment, your Movement Ratio and CS Response Strength windows should resemble the following.

During acquisition, the movement ratio starts at 0 on the first trial, then rises and levels off at about 0.7. This increase in the movement ratio means that the tone CS is acquiring the capacity to induce freezing and other fear-related behaviors. As the movement ratio increases, the CS Response Strength mind window shows that the toneâs capacity to elicit fear as a psychological process is increasing. Remember that the Movement Ratio window depicts a change in Sniffyâs behavior, whereas the CS Response Strength mind window depicts the change in Sniffyâs psychological state that influences the behavioral change.

With a real rat, the animalâs changing response to the CS would be the only thing that a psychologist could observe. Many psychologists explain this behavior change by postulating that it results from a change in an unobservable psychological process. With the conditioned emotional response, the acquired capacity of a CS to elicit freezing and to suppress bar pressing or other operantly conditioned behaviors is thought to be the result of an increasingly intense fear response. During CS presentations, Sniffyâs Sensitivity & Fear mind window displays the strength of Sniffyâs current fear; and the CS Response Strength mind window shows how strong the fear response will be when the CS is presented the next time. With Sniffy Pro, you can observe both the behavior change and the change in the Sniffy Pro programâs classical conditioning algorithm÷Sniffyâs psychological state÷that causes Sniffyâs behavior to change. We have designed Sniffyâs classical conditioning algorithm to resemble theoretical processes that psychologists (for example, Guthrie, 1960; Hull, 1943, 1952; Rescorla & Wagner, 1972) have postulated in an effort to explain classical conditioning. However, nobody has ever seen anything closely analogous to CS response strength in a ratâs brain; and many psychologists assert that itâs impossible, even in principle, to observe the psychological (mental) processes of real animals. We believe that the Sniffy Pro programâs mind windows will help you understand psychological explanations of classical conditioning, but itâs important to remember that they do not provide any deep insights into the workings of the ãanimal mind.ä

Exercise 2: Extinction

These instructions assume that you have already run the acquisition experiment described in Exercise 1. To set up a series of 30 extinction trials, you should follow the steps listed. You need to give more extinction than acquisition trials because the CER extinguishes much more slowly than it is acquired.

• Continue with the file that we suggested you name Ex1-ClassAcq in which Sniffy acquired a CR to the medium-intensity tone CS.
• Use the Save As command to save the file under a new name (e.g., Ex2-ClassExt) in the Sniffy Files folder on your computerâs hard drive. Saving the file under a new name preserves the original file in which Sniffy has been classically conditioned for future use. You will need it for several future exercises.
• Choose the Design Classical Conditioning Experiment command from the Experiment menu. The Classical Conditioning Experimental Design dialogue box opens to Stage 1. All the options for defining conditions are dimmed because Stage 1 has already been run.
• In the Design Classical Conditioning Experiment dialogue box, make the following settings to define Stage 2, which will contain your extinction trials:
  • In the Stage section, click on the command button labeled New Stage. The number after View/Edit Experimental Stage changes from 1 to 2 to indicate that you are now working on Stage 2 of the experiment. Because this is a new stage that has not yet been run, all the options for defining trial types are available.
  • In the Stage section, be sure that the numeral 5 appears in the text box after Interval Between Trials, and type 30 in the text box located to the right of Present Each Trial Type. These settings indicate, respectively, that the average interval between trials will be 5 minutes and that there will be 30 trials for each Trial Type.
  • In the First Stimulus panel, choose the medium-intensity tone.
  • In the Second Stimulus panel, choose None.
  • Carefully check your settings.
  • Click on the Save button at the bottom of the dialogue box to save the experimental design.
• After the Classical Conditioning Experimental Design dialogue box closes, choose the Run Classical Conditioning Experiment command from the Experiment menu.
• If you want to speed up the experiment, select the Isolate Sniffy (Accelerate Time) command from the Experiment menu. Because you will need to use the file from this exercise as the starting point for the next exercise, you want to avoid inadvertently letting the program run for very long after this exercise is complete.
• When the program has finished running the experiment, choose the Save command from the File menu to save your results.

During the next 150 minutes of program time, the Sniffy Pro program will automatically give Sniffy 30 extinction trials÷that is, 30 trials during which the CS occurs without the US. As the program executes, the Sniffy Pro program will draw a graph showing Sniffyâs movement ratio on each trial in the Movement Ratio window and the strength of the toneâs capacity to elicit fear at the end of each trial in the CS Response Strength window. At the end of extinction, your Movement Ratio and CS Response Strength windows should resemble the following.

The Movement Ratio window shows that repeatedly presenting the CS without the US causes the CS to gradually stop eliciting freezing and other fear-related behaviors. The CS Response Strength mind window shows that this behavior change is the result of the CSâs losing its capacity to elicit a fear response. Once again note the variability in the movement ratio that reflects the probabilistic nature of Sniffyâs behavior.  

Exercise 3: Spontaneous Recovery

Here are the steps that you need to follow to observe spontaneous recovery.

• Continue with or open the file that we suggested you call Ex2-ClassExt from Exercise 2, in which Sniffy was first conditioned in Stage 1 and then extinguished in Stage 2.
• Use the Save As command to save the file under an appropriate new name (e.g., Ex3-ClassSponRec) in the Sniffy Files folder on your computerâs hard drive.
• Under the Experiment menu, choose Remove Sniffy for Time Out. This operation simulates removing Sniffy from the operant chamber and leaving him in his home cage for 24 hours; a dialogue box will appear telling you that Sniffy has left the chamber. To return Sniffy to the experiment on the next simulated day, click the OK button in the dialogue box.
• Choose Design Classical Conditioning Experiment from the Experiment menu and make the following settings in the Classical Conditioning Experimental Design dialogue box to give Sniffy a second 15-trial extinction session:
  • The dialogue box opens (as always) to Stage 1. All alternatives for defining trials and stimuli are dimmed because Stage 1 has already been run.
  • To define a new Stage 3, you must first move to Stage 2 because new stages are always inserted immediately after the stage currently being displayed. In the Stage section of the dialogue box, click on Next Stage to move to Stage 2, which has also already been run.
  • When you reach Stage 2, click on New Stage to create the new Stage 3 after Stage 2. Note that the numeral 3 is now present after View/Edit Experiment Stage.
  • Make sure that the Interval Between Trials is set at 5 minutes.
  • Set Present Each Trial Type to 15 times.
  • In the First Stimulus panel, choose the medium-intensity tone.
  • In the Second Stimulus panel, choose None.
  • Carefully check your settings.
  • Click on the Save command button at the bottom of the dialogue box to save the experimental design.
• After the dialogue box closes, choose the Run Classical Conditioning Experiment command from the Experiment menu.
• If you want to speed up the experiment, select the Isolate Sniffy (Accelerate Time) command from the Experiment menu.
• When the experiment has finished running, save the file.

As Stage 3 executes, the movement ratio will be graphed as a function of trials in the Movement Ratio window, and the strength of the toneâs capacity to elicit a fear response will be graphed in the CS Response Strength mind window. At the end of the experiment, these two windows should resemble those shown next.

VERY HELPFUL  FEATURES in Pro Version 2.0

Accelerating Time

Some of the Sniffy Pro experiments that you will be performing require several hours of both clock time and program time to complete. To enable you to run long experiments faster, we have made it possible for you to make Sniffy invisible so that your computer can run the experiments as fast as possible. Selecting the Isolate Sniffy (Accelerate Time) command from the Experiment menu simulates speeding up time. To make Sniffy visible again, click on the handle in the isolation window or choose the Show Sniffy command from the Experiment menu. The Isolate Sniffy (Accelerate Time) and Show Sniffy commands replace each other in the Experiment menu. The Isolate Sniffy (Accelerate Time) command is available whenever Sniffy is visible. The Show Sniffy command is available whenever Sniffy is isolated.

Noise Control

Sniffyâs classical conditioning exercises make frequent use of a tone as the CS. By default, that tone will be played at appropriate times whenever Sniffy is visible during classical conditioning experiments. If you, your family, or your roommates want peace and quiet, you can silence the sound by executing the Preferences command in the Sniffy menu and selecting the Sound Proof Cage option.

That is the end of Project 3. Thank you for taking the time to tour our website and get familiar with some of the features of Sniffy, the Virtual Rat (Professional Edition).