The purpose of this experiment was to test whether training a simulated rat under a Partial Reinforcement Schedule took longer to extinguish than being trained in a Continuous Reinforcement Schedule. The subject involved was a computer based rat. The rat was trained in a Skinner box to bar press under each a continuous reinforcement schedule and a partial reinforcement schedule. Extinction of both schedules was done and times were reported. The hypothesis was that a rat under a partial reinforcement schedule would take longer to extinguish its behaviour rather than the continuous reinforcement schedule extinction. Results were analyzed under the complications of the conditioning of the animal under these schedules.
Studying the behaviours of animals has been a great importance to many psychologists. By studying animal behaviours, researchers can determine what influences them, whether it is their surrounding environment, reinforcements or stimuli. A very famous psychologist, Burrhus Frederic Skinner enjoyed studying animal behaviours. Skinner believed that any response that is followed by a reinforcing stimulus tends to be repeated (Hergenhahn and Olson, 2005). He also says that to modify a behaviour, one merely has to find something that is reinforcing for the animal whose behaviours one wishes to modify (Hergenhahn and Olson, 2005). Skinner explains this in his Skinner box studies.
A Skinner box refers to an experimental test chamber that consists of a grid floor, lever, light and food cup (Hergenhahn and Olson, 2005). Mainly used to study operant conditioning, which refers to increasing the rate at which a response occurs (Hergenhahn and Olson, 2005). These studies involve rats and observing the rat in the Skinner box. The rat receives food pellets through the feeder which is accompanied by a clicking noise. Skinner magazine trained the rat which involves training the animal to approach the food cup when it hears the clicking noise and/or seeing the food come out of the food cup. This noise is then associated with the food. After several trials of this, the rat left to bar press by itself and when the rat does bar press, this response is reinforced with food which tends to be repeated. The more times this occurs, the higher the probability the response will occur again.
To shape an animal, the experimenter reinforced rats’ behaviour when it’s close to the feeder and therefore the rat tends to stay close to the feeder because of being reinforced. Shaping occurs when the rat bar presses on its own. This is done by successive approximation which is the response the rat makes is very similar to the response the experimenter wants to reinforce (Hergenhahn and Olson, 2005). These trials occur through acquisition trials. This is the process of gaining new information from one’s observations (Hergenhahn and Olson, 2005).
This rat is under a continuous reinforcement schedule which where the rat is reinforced every time it makes an appropriate behaviour (bar pressing on its own). Partial reinforcement schedule is where the rat only gets reinforced sometimes when it bar presses, and unlike the continuous reinforcement which is all the time. Extinction of the rats’ behaviour plays a large role in which schedule the rat has been trained under. When the rat’s behaviour is extinguished, the rat no longer bar presses to get food because it no longer “believes” the act will produce a reward.
This study is important because the conditioning that occurs during the different schedules is related to how easily the animal extinguishes its behaviour. Time is a factor in this experiment. It is hypothesized during this study that the partial reinforcement schedule will take longer to extinguish than the continuous reinforcement schedule. It is believed that partial reinforcement is harder to extinguish because the animal sometimes receives reinforcement and sometimes does not. But the rat still makes an effort to try and see if bar pressing will end in a reward. Continuous reinforcement extinguishes faster because the animal has always been reinforced and has never been lead to believe that the next bar press might not produce a reward, and during extinction, it gives up quickly. Method
The equipment used to carry out this experiment was a computer based program located on the St. Francis Xavier University server. The program called “Sniffy- The Virtual Rat” generated the realistic responses of a rat. This program allowed experimenters to humanely learn about rats and their behaviours when placed in a Skinner box. This program simulated what a typical rat would do on a typical day in a Skinner box. Procedure
After accessing the computer program on St. Francis Xavier’s server, the virtual rat (the subject) was shown to be wandering around the Skinner box. During the first project, the experimenter observes Sniffy’s behaviour. This rat is untrained and had to previous testing or training. For the first 10 minutes, the experimenter observed Sniffy’s behaviour and becomes familiar with the rats’ repertoire of behaviour. These behaviours are referred to as baseline behaviours. After observational behaviour, the baseline frequency of bar pressing per minutes is established. The cumulative record displayed on the screen shows ticks representing the number of bar presses the rat has made. This number is divided by 10 to calculate the number of bar presses per minute.
Magazine training follows bar pressing response rate. At the back of the Skinner box, is where the hopper and/or magazine is located. This is where the food comes out of. The experimenter rewards Sniffy with a food pellet when he comes near the magazine. Sniffy will eat the food and then the experimenter will give Sniffy another one after he finishes the first pellet. Training repeats for 10 to 15 reinforces. By this time, Sniffy is trained to approach the magazine whenever a food pellet is delivered. This is tested when Sniffy is located in a corner and a food pellet is delivered and Sniffy comes over and eats the pellet.
The next procedure, shaping by successive approximations, shapes Sniffy’s bar pressing behaviour. To do this, the experimenter reinforces Sniffy for behaviours that are similar to the bar pressing response. This process gets Sniffy to realize that bar pressing results in reward and producing behaviours similar to bar pressing also results in reward. This stage is completed when Sniffy bar presses four to five times within one minute. The experimenter discontinues manually giving Sniffy a food pellet which allows Sniffy to bar press on his own. This is visually completed when the cumulative record resets (peaks) a second time. Sniffy is now trained and at this stage, saving the trained Sniffy occurs. Experimenter exits the program and re-opens Sniffy under a continuous reinforcement schedule and is let to run around for a bit
The next stage is extinction. Extinction is chosen from the Parameter section of the Training Schedule toolbar. During this time, Sniffy does not receive any reinfrocment for bar pressing, which he continues to do. The experimenter timed and reported extinction baseline. This also indicated to count the amount of non-reinforcing bar presses Sniffy maked. Bar pressing is extinguished when Sniffy bar pressed less than three to five times in five minutes. Saving the experiment under a new file name happens during this point.
The next stage is spontaneous recovery, where Sniffy was removed from the Skinner box for a time out. Reporting the number of bar presses Sniffy makes within the first two minutes of spontaneous recovery occurs here. Saving occurs here and so does printing of the cumulative records.
The second part of the Sniffy experiment involves schedule of reinforcement. Sniffy is placed under a partial reinforcement schedule (this Sniffy is not the one who was just trained under a continuous reinforcement schedule, the trained Sniffy, saved the first time is used here). Observing Sniffy’s bar pressing rate for the first minute occurs here. Now changing Sniffy to a Fixed Ratio of 25 schedule, which is selected under the training schedule. This process occurred slowly because giving Sniffy a large interval would cause him to extinguish. Sniffy’s behaviour. Working in intervals of five worked best for this experiment. Sniffy received 10 pellets during each interval, concluding that he has been trained under the new schedule. When Sniffy successfully received 10 pellets from each of the five intervals (up to 25), Sniffy is now trained under fixed ratio 25. Extinction followed training. Extinction was chose from the training schedule. The number of Sniffy’s non-reinforced bar presses was recorded. Training was also done under a variable ratio of 25 (with the trained Sniffy, not the extinguished one). The same process was done for the variable ratio 25 as it was for the fixed ratio 25 and extinction followed. This was the end of the experiment. Results
During project one, Sniffy’s behaviour during observational behaviour consisted of Sniffy smelling, wandering around the box, drinking water, scratching ears, body, he also cleaned himself, looked up towards the ceiling and fixated on the wall and touched the wall by standing up on it.
Sniffy’s bar pressing response rate after observation was zero. He displayed no bar pressing during this time. In appendix A, this can be seen by a straight line at the beginning of the cumulative record which continues for roughly 20 minutes.
Magazine training took roughly 22 minutes and within that time, Sniffy did display some bar pressing. During shaping by successive approximations, training Sniffy took a long period of time. From beginning to acquisition, the time frame was roughly 87 to 90 minutes. At this time, Sniffy was trained. Sniffy’s behaviour at acquisition was bar pressing continuously, he did not move away from the magazine, still cleaned, scratched and licked himself in between bar pressing. Sniffy did not go towards the front of the box at all. Sniffy continued to drink water also. Sniffy’s rate of responding when trained was 61 bar presses within 10 minutes. In appendix A, acquisition is labelled. Extinction was instituted roughly around the 95 mark. Extinction was complete roughly in four minutes after instituted. Sniffy produced 15 non-reinforcing bar presses after extinction was initiated. During spontaneous recovery, Sniffy bar pressed 10 times within the first two minutes. It took Sniffy to extinguish the behaviour in approximately three and half minutes. Appendix A also shows where spontaneous recovery occurred.
During project two, in the trails of fixed ratio 25, Sniffy does continue to bar press after changing from a continuous reinforced schedule to a partial reinforced schedule. This process took a long time to accomplish. This process can be seen in Appendix B where each interval is reported (this sheet is double sided, where extinction is on the reverse). Throughout the trials of fixed ratio 25, extinction was instituted at 135 minutes and extinction was completed at143 minutes and therefore the extinction baseline was seven minutes. Within the first two minutes of when extinction was initiated, Sniffy bar pressed 81 times, without being reinforced.
For the variable ratio of 25, Sniffy continued to bar press after being switched from a continuous reinforcement schedule to a partial reinforcement schedule. This process took the longest time to accomplish. This can be seen in appendix C, on both sides of the paper. The extinction was instituted at 133 minutes, and completed at 148 minutes. Extinction baseline was 15 minutes. Within the first two minutes of extinction, Sniffy bar pressed 41 times. Discussion
With thorough assessment of appendix A, will show that during continuous reinforcement schedule and during institution of extinction, Sniffy bar pressing was very low, compared to the other trials. Sniffy shows extinction rather fast. Continuous reinforcement does produce fast extinction because Sniffy in this schedule always received rewards (food) therefore always content (a response that leads to a satisfying state of affairs is likely to be repeated). Sniffy never had to feel frustrated that he never received food during bar pressing. When Sniffy is in the extinction trial, he learns fast that there is no food when he bar presses which leads to frustration and shortly after gives up. Sniffy made the avoidance response, he never learnt that sometimes a reward comes, learnt all the time that the reward comes.
In appendix B, Sniffy is in the continuous reinforcement schedule and under fixed ratio trials and after viewing the cumulative records, Sniffy steadily bar presses after extinction is initated. He then steadily bar presses a little more then slows down. Sniffy does not extinguish fast but faster than variable ratio. Sniffy learnt that pressing the bar so many times produces food. Sniffy does get frustrated because in acquisition he learnt to approach the bar press and now there is no food.
Variable ratio took the longest time to extinguish because counter conditioning occurred. Sniffy produced tendencies of the approach response but frustration response at the same time. These are incompatible (approach-avoidance conflict). This is why in this trial, Sniffy’s cumulative record continues to increase, and performance is still being maintained. Sniffy gets frustrated, and he learnt to approach the bar press when frustrated. This took the longest because of the variable ratio, Sniffy was not able to know when the food would come out, sometimes it would sometimes it would not. This made him keep going and testing the bar press.
Therefore, animals in the partial reinforced schedule do take longer to extinguish because they learnt to make the approach response, and even when frustrated. The frustration drove the animal to continue to approach and not give up. The continuous reinforced trial extinguished so fast because the animal has never been in the situation of not getting reinforced therefore not making the approach response, making the frustration response and therefore the behaviour ceases.
Hergenhahn, B.R. & Olson, M.H. (2005). An introduction to theories of learning (7th ed.). New Jersey: Prentice Hall.