Creating and Extinguishing a Classically Conditioned Reflex

Transcription

1 Laboratory 1 Creating and Extinguishing a Classically Conditioned Reflex Background Information In this experiment, you will be investigating classical conditioning. Remember that classical conditioning occurs when a stimulus (the conditioned stimulus or CS, e.g., a bell, a word) is repeatedly paired with another stimulus (the unconditioned stimulus or UCS, e.g., smelling pepper or seeing a smiling child) that evokes a reflex (the response, e.g., sneezing or feeling happy). In particular, you will be investigating how quickly classically conditioned associations go away (or extinguish) when the CS is no longer presented with the UCS. Classical conditioning is very important in our daily lives. Previous research has suggested that many of the emotional reactions that we have to stimuli may be classically conditioned. For example, as a child, you may have come to like a friend because you had fun playing with her. In this Pavlovian example, the CS, your friend, became repeatedly paired with the UCS, having fun. In turn, the positive emotions that you felt as a result of having fun became associated with your friend and as a result you came to like her. In a more serious context, classical conditioning can also affect our tolerances to drugs. For example, if a heroin user repeatedly self-administers heroin every day at 5 PM while listening to a Pearl Jam CD, the environment (the room, time and music) become a conditioned stimulus that lets the users body know that an injection of heroin is soon to follow and therefore the user s body should be prepared to process the drug as quickly as it can (a set of processes that together comprise the conditioned response). This early warning leads to a tolerance that is context specific. That is, when the CS is presented, the CR occurs and an appropriate response to the drug decreases its effect. In response to this, users will often increase the amount of a drug that they use. Ultimately, this can lead to serious problems if the user then administers this larger dose of the drug in a different context. Without the CS to engage the body s tolerance, the larger drug dose will not be effectively processed and an overdose is likely to occur. In fact, work by Shepard Siegel suggested that a large percent of all fatal drug overdoses occur with a dose of the drug that is not significantly larger than the user s normal dose. As you might imagine, in both of these examples, a change in the relationship between the UCS and the CS will lead to a change in the response that is elicited. For example, if you spend a large amount of time with your friend without having fun (the CS in the absence of the UCS), eventually the response (positive emotions) will diminish and go away. Similarly, if the heroin user stops using heroin, but still listens to Pearl Jam at 5 PM every day, eventually his body will stop anticipating the injection and his context-specific tolerance will fade. These two examples demonstrate the process of extinction. In this lab, you will test if the number of times a UCS and a CS are paired affect the length of time necessary for the conditioning to extinguish.

2 Data Collection Worksheet Participant Gender Participant Age Participant Group Positive Trials Negative Trials Lab Report Information In this lab report you will be responsible for filling in four types of information. First, you should fill in the appropriate references in the introduction. You can get the necessary information from the reference list included after the discussion section. You may use your textbook as a model for what citations in text should look like. Second, you will need to fill in information in the methods section that details what you did and to whom you did it. All of the information you need to record from your participant is indicated on the data collection worksheet. After data collection, you will combine this information with information from the others in your class to provide an account of the demographics your sample. Finally, you will have to fill in information detailing precisely how you manipulated and measured your variables. Third, you will need to perform some calculations on your data. In order to describe your results for each group, you should calculate the mean number of positive trials for each group. Further, to give your reader some idea of how spread out the scores were in each group, calculate the standard deviation of each group as well. We will do this as a group. Finally, you will need to fill in three parts of the discussion. In the first paragraph you will summarize your results. In the second paragraph, you will describe an original practical application of these results. In the third paragraph, you describe another study that could be done in this area that might shed more light on these phenomena (e.g., Will this result hold for all people? Will it work for all reflexes? How could you have made this study better?, etc.)

3 Lab Report Introduction Classical conditioning is one of the most fundamental types of learning. In a serendipitous discovery, Pavlov ( ) showed that when dogs are repeatedly given food in the presence of some unrelated stimulus (e.g., the ticking of a metronome), eventually, the unrelated stimulus comes to elicit the same reflex as the food (i.e., salivating). Following this realization, many studies have later confirmed that repeatedly presenting a novel stimulus followed by a reflex eliciting stimulus (called an unconditioned stimulus, or UCS), would cause the novel stimulus (now called the conditioned stimulus, or CS) to come to elicit the reflex even in the absence of the UCS. Despite its simple beginnings, classical conditioning has been shown to play an important role in people s everyday lives. Aside from the amusing but ultimately trivial abilities of making a hapless participant salivate, sweat or sneeze on command, classical conditioning can fundamentally alter everything from our preferences to our immune functioning. For example, Zajonc and Murphy ( ) demonstrated that pairing Chinese ideographs with happy or angry faces caused participants to like or dislike the ideographs respectively. Even more importantly, previous research has suggested that a large percentage of heroin overdose fatalities are due to context-specific drug tolerances a classical conditioning phenomenon ( ) Because of the wide ranging consequences of classical conditioning, it is important to learn about the variables that can influence the strength of the CS-UCS relationship. One variable that may be important is the number of times that CS and UCS are paired during conditioning. It stands to reason that more pairings will lead to a stronger association between the CS and UCS. Therefore, it is hypothesized that more pairings of the CS and UCS will cause the CS-UCS relationship to last longer, even after the pairing of the two stimuli has stopped. Method Participants. Participants were. Of the participants, were female. The average age of the participants was. They participated in the experiment. Materials. To perform the classical conditioning, participants patellar tendon was stimulated by. The stimulus with which the reflex was paired was a. Procedure. Upon arrival at the lab, participants were randomly assigned to one of two groups. participants were assigned to the more trials condition, whereas participants were assigned to the fewer trials condition.

4 Learning Phase. Both groups of participants were conditioned in the following manner. Participants were exposed to the (hereafter, referred to as the CS), and were then struck on the patellar tendon with a (hereafter referred to as the UCS). The UCS CS pairing was repeated times for the participants in the more trials condition and times for the participants in the fewer trials condition. Evaluation and Extinction Phase. Upon completion of the learning phase, the strength of the participants CS-UCS association was tested. To perform this test, participants were presented with the CS in the absence of the UCS 15 times. Each presentation of the UCS was evaluated as either having generated a response (a positive trial) or having generated no response (a negative trial). The criterion used for declaring a trial positive was. The number of positive trials was summed for each participant, giving each an extinction score, with higher numbers indicating a longer extinction period. Results After the extinction scores for each participant were compiled, means for the more trials condition and fewer trials conditions were computed. The average for the more trials condition was positive trials (standard deviation: ). The average for the fewer trials condition was positive trials (standard deviation: ), see Figure Positive Trials More Trials Group Fewer Trials Group Figure 1. Mean number of positive trials as a function of number of learning trials. In order to assess whether the two experimental groups differed from each other significantly, a t-test was performed. Results suggest that, t( ) =, p.

5 Discussion Summarizing, the results of this study indicate that This result has many practical applications of this result, including A follow-up study that could be done to expand upon this finding would be,

6 References Murphy, S. T, & Zajonc, R. B. (1983) Affect, cognition, and awareness: Affective priming with optimal and suboptimal stimulus exposures. Journal of Personality and Social Psychology,64, Pavlov, I. (1927, reprinted 1960) Conditioned Reflexes (G.V. Anrep, Ed. & Trans.). New York: Dover. Shepard, S. (1984). Pavlovian conditioning and heroin overdose: Reports by overdose victims. Bulletin of the Psychonomic Society, 22,