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Home Up Apparatus Equipment Test Experiment 1 Experiment 2 Experiment 3 Experiment 4 Experiment 5 Experiment 6

Experiment 4: Fixed Ratio Schedules and Extinction

Purpose:

To gradually implement a fixed ratio (FR10) schedule of reinforcement. This will be followed by an extinction period to determine the effect of partial reinforcement.

Procedure:

  1. Do an equipment test.
  2. Notify the TF when you are ready to begin the experiment.
  3. Turn on the house light by pressing the hand switch once. Then place your animal in the operant chamber.
  4. The first 10 reinforcers can be delivered either by the animal lever pressing or manually by pressing your hand switch.
  5. Now begin implementing a FR schedule. You will begin with a FR2 schedule and gradually work up to a FR10 schedule. You will be recording the number of responses per minute from now until the end of the experiment. The external light will flash at the end of each minute. Important to note is that from now until the end of the experiment reinforcers will not be delivered automatically. You are required to press the hand switch to signal that the next lever press should be reinforced. The reason for this is to give you direct control over your subject’s FR schedule.
  6. FR2 schedule. The goal is to reinforce the animal for every second lever press. Allow him to lever press once – this press will not be reinforced. Then press your hand switch to signal to the computer that the next lever press should be reinforced. Continue this procedure until the end of the minute during which the 10th reinforcer occurs.
  7. FR3 schedule. Allow the subject to lever press twice without being reinforced. Then press your hand switch to signal that the next press should be reinforced. Continue this procedure until the end of the minute during which the 10th reinforcer occurs.
  8. In the same manner, gradually increase the FR schedule to FR4, FR6, FR8 then FR10. Each schedule should continue until the end of the minute during which the 10th reinforcer occurs. NOTE: Follow this procedure only if your animal moves easily from ratio to ratio. If your rat stops responding for a considerable period of time, you will have to modify the procedure by returning to a lower ratio and then gradually increasing the ratio once again.
  9. At the end of the FR10 schedule, implement the extinction phase. Do not reinforce bar presses for 15 minutes but continue to record the number of bar presses per minute. Make a note on your records at which minute extinction began.
  10. . The house light will go off and the experiment will end either after the delivery of 120 reinforcers or after 90 minutes, whichever occurs first.

Data Collection:

Before coming to class, prepare a data sheet. You will be recording the number of responses per minute during each of the FR schedules and during the 15-minute extinction period. It is important to note on your sheet which FR schedule you are in and when the extinction phase starts.

Group Data:

Submit your group data before leaving class.

 

Number of responses:

Last 3 mins FR10

 During the fifteen minutes of extinction following FR10.

1

2

3

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15
                                   

 

 Lab Report # 2

You will be required to present the data from this laboratory graphically with a view to answering the following questions:

Note: You will require data from Experiment 3.

  1. Was there a change in the pattern of responding during this experiment? You will be given a computer generated cumulative record. Use this figure to describe what happened during the experiment.
  2. Did your subject show a different pattern of responding at different FR levels?
  3. Is there evidence of the partial reinforcement effect for your subject? For the group?

MED-PC Output

Array A – the number of responses before each reinforcer after the initial 10.

Array C – used to generate a cumulative record

Array D – the number of responses per minute

Fixed Ratio Schedules And Extinction Program.