Sniffy Assignment #1 - Basics of Classical Conditioning

due Tuesday, Feb 28

In this assignment you will classically condition your rat and investigate the CC phenomena of blocking and overshadowing. Collaboration is not allowed, you should complete this assignment on your own.

READINGS: Before beginning the assignment make sure you have read Chapters 1-4 of the Sniffy Pro Book. Make sure you have also read the appendix, How to Manage Your Sniffy Pro Files. Some of these simulations can take some time to complete. You should use the Accelerate Time command from the Experiment menu, or the sessions will take hours.

Please read the following instructions in their entirity before proceeding.

1. You will start by classically conditioning your rat to fear a medium intensity tone. To do this, follow the instructions for Exercise 1 (p 37). You will be using the suppression ratio as your response measure (review your notes so you are comfortable with what this shows), so you will need to begin with a rat fully trained on a VR-25 schedule as mentioned in the Exercise 1 instructions (there is one included in the Sniffy sample files folder that came on your CD). Since you will be using the suppression ratio as your response measure, be sure this window is visible. Save this rat when you have completed the exercise.

A VR-25 schedule (variable-ratio 25 schedule) means that your rat gets a reinforcer (food pellet) after approximately 25 bar presses. (The number of bar presses will average out to 25, but on one trial he may only have to press it 24 times and the next trial 26 times, etc.)

2. Extinguish the fear response by following exercise 2, and save this rat (see file naming in Exercise 2).

3. Demonstrate spontaneous recovery by completing exercise 3, and save this rat (see file naming in Exercise 3).

Follow the instructions for exercise 7 to demonstrate blocking.

4. Starting again with a new VR-25 rat (open the one in the sample folder again, do not use the rat you extinguished above), set up an overshadowing experiment by pairing a high intensity stimulus and a low intensity stimulus as the first stimulus and the shock as a second stimulus. Follow the instructions for Exercise 8.

5. As noted in your Sniffy Pro book, the appropriate control condition for the overshadowing experiment is a compound conditioning experiment. Starting with a new VR-25 rat, set up a compound conditioning experiment where a light and a tone are paired with a shock in stage one, and then in stage two each stimulus is presented on its own (see instructions for Exercise 6).

6. Do an experiment to determine which stimuli is more salient, a medium intensity light or the bell.

The Homework Write Up

Be sure to read page 31 on how to copy images from Sniffy to another program.

For your write up you will need to answer the following questions.

1. Give a brief description of what you did during this assignment.

2. Identify the UC, UR, CS, and CR in this experiment.

3. What is the duration of the CS in Sniffy Exercise one? The Sniffy program calculates the suppression ratio for you. Give the formula for calculating suppression ratios and use it to calculate the suppression ratio of the cumulative record below (the cumulative record is covered in the sniffy book as well as chapter 2 of your textbook p. 56).

4. Include a copy of your suppression ratio window following conditioning of a medium intensity tone and shock.

5. Include a copy of your CS response strength window from the spontaneous recovery experiment. Describe what the data is showing and how spontaneous recovery is indicated (explain what spontaneous recovery is in your answer).

6.Include a copy of your CS response strength window from the blocking experiment. Show the suppression ratio window from the blocking experiment. How does the suppression ratio window show that blocking has occurred?

7. First explain what compound conditioning is, and why that is a proper control for the overshadowing experiment.

8. Show the CS response strength and suppression ratio windows for the overshadowing experiment and the compound conditioning experiment. This menas that you should include two CS response strength windows and two suppression ratio windows. Be sure to label each window correctly. Explain what the data indicate and what conclusions can be drawn for these experiments.

9. Which is more salient, the medium intensity light or the bell? Show data to support your answer.