Abstract
Kamin blocking is a condition where animals elicit a Conditioned Emotional Response (CER) to a Conditioned Stimulus (CS) and fail to associate any other Unconditioned Stimulus (US). This study investigates if the Kamin blocking principle holds true for human subjects. Using food as a conditioned stimulus and Allergic reaction as an unconditioned stimulus, a contingency judgment task experiment was conducted on 683 participants, where they were exposed to a CS in the first stage and a combination of CS, US and a superimposed stimulus in the second stage. In the third stage. Participants asked to predict the probability of the superimposed stimulus eliciting the US and compared with the control group, who were not conditioned to the CS. The results of the experiment are discussed below.
Kamin Blocking Revisited
Pavlov first showcased the effects of classical conditioning with the famous experiment where a dog was conditioned to respond to an Unconditioned Stimulus (US) because of its association with a Conditioned stimulus (CS). However, a lot of questions regarding Classical conditioning were yet to be answered. What is the relation between a conditioned stimulus and an unconditioned stimulus? How do animals create an association between the CS and US so as to elicit a Conditioned Emotional Response? Most importantly what are the governing factors behind a successful classical conditioning experiment?
Kamin Blocking is an interesting concept that was first proposed by Leon Kamin, in the 1960s . This theory arose as a result of the research on Conditioned Emotional Response(Estes & Skinner, 1941; Malott & Trojan, 2008) with shock as one of the Unconditioned Stimuli(US). Kamin raised questions about the role of the type of stimuli on Pavlovian conditioning or Classical conditioning(Pavlov, 1927). The tenets of Pavlovian conditioning only talk about the presentation of a Conditioned Stimulus in association with an Unconditioned Stimulus. Kamin asked, what if a compound set of CS were presented along with a US? How would the animal get conditioned to the CS and its constituent elements? And finally how can the attention of the animal be redirected through experimental manipulations. The experiments conducted by Kamin clearly showed that animals once exposed to a Conditioned stimulus choose to ignore the Unconditioned stimulus, this ‘blocking’ happened because the US was not very informative compared to the CS and not because animals ignored all other stimuli apart from the CS (L. J. Kamin, 1961,1968; Pavlov, 1927) . The blocking experiment by Kamin clearly reasons that a mere association of a CS with a US is not enough to elicit a CR. Kamin first conceived the blocking concept as a competition between the conditioned elements versus the superimposed element to elicit the CR.
Marchant & Moore, (1973) conducted a similar experiment that effectively blocked the nictitating membrane response in rabbits, which is still considered one of the classic independent examples of Kamin blocking. Another very interesting example of Kamin blocking was demonstrated by Sahley, Gelperin, & Rudy, (1981), where they used one-trial associative learning techniques to alter the food preferences of mollusks.
In this modern reiteration of the Kamin blocking experiment, 683 Psychology students participated in a simulated contingency judgment experiment, where they were asked to identify an allergy inducing food item based on the reactions of an imaginary patient. Based on this design, students were exposed to CS in the form of an allergen Food 1 and US allergic reaction and then exposed to a combination of CS, US and a Superimposed Stimulus of Food 2 . In the final test, students were only exposed to the US and asked to predict the probability of Food 2 eliciting an allergic reaction. It is hypothesized that students already exposed to the CS will most likely showcase classic Kamin blocking and become unreceptive towards the US, while the control group will be more likely to respond to US and vote for Food 2 as a possible allergen.
Method
Participants
683 first-year psychology students (243 males and 440 females) of mean age 19.2 years participated in this experiment. The participants were divided into a test group (n=340) and a control group (n=343).
Design
The experiment was designed to showcase Kamin blocking principle on human subjects. Participants were asked to rate the probability of a particular Food 1 (CS) causing an allergic reaction in a patient. The independent variable for this study was exposure to Food 1, which was the CS (Conditioned Stimulus). The test group was conditioned to a particular food item causing allergic reaction (Unconditioned Stimulus) and the control group was not conditioned. In the first stage of the experiment, participants of the test group were conditioned to Food 1 allergy parings. In the second stage, both the control and test group were exposed to a combination of Food1 +Food 2 allergy pairings. In the final stage both groups were exposed to the Food 2 and asked to rate the probability of occurrence of an allergic reaction. The Dependent variable for the test was the participant’s rating of the probability that the Food 2 could have been the reason behind the allergic reactions
Materials
The experiment was conducted on computers in a classroom setting using a contingency judgment task on a HP desktop computer and a Dell U2311H 60Hz LCD monitor. The MATLAB Software (MathWorks, 2004) was used for stimulus presentation.
Procedure
The participants were asked to imagine themselves as physicians trying to detect the foods (CS) that can cause allergic reactions (US) to an imaginary patient. The participants were shown a combination of food items consumed by the imaginary patient and asked to predict if there would be an allergic reaction. Participants selected the food item they thought created an allergic reaction by clicking on a box nest to it. Once an outcome was selected, the participants were shown the actual results (if allergic reaction occurred or not). There were 2 groups and 3 stages in the experiment. In stage 1, participants in the experimental group (n=340, mean age=19.2 years, 221 females) were exposed to Food1 allergy. In stage 2, they were exposed to Food 1+ Food 2 allergy pairings. In the stage 3 participants were asked to rate (using a visual analogue scale on the computer screen) how likely they thought, Food 2 could be responsible for allergic reaction in the patient. The probability ratings of the experimental group was compared to that of the control group (n=342, mean age=19.2 years, 219 females). The control group was not exposed to Food 1 and therefore were not conditioned to it. 18 other random food items were embedded with food 1 and food 2 to ensure classical conditioning. Food 1 and Food 2 was randomly assigned to participants, to account for guesswork and manipulation.
Results
The mean probability rating for participants choosing Food 2 in the third stage of the experiment was compared between the control and the test groups and shown in Table 1. Independent-samples t-test was conducted between the mean probability ratings for the control group choosing Food 2 (0.62±0.01) was found to be significantly higher than the test group (0.44±0.01), t(683)=14.7,p<0.00001. This shows that the test group effectively blocked the Food 2 and did not consider it to be a possible cause of allergy. This simply shows that the participants of control group, who were not conditioned to the Food 1 had a higher chance of choosing Food 2 as one of the possible causes of an allergic reaction. While the Test group participants were already conditioned to the Food 1 and ignored the Food 2 during the stage 2 of the experiment and thus were less likely to identify Food 2 as a possible allergen.
Mean probability ratings, standard error of the mean for the Food 2 being the cause of allergic reaction to the patient
Discussion
The results of the experiment showed that participants of the test group, who were conditioned to Food 1 as the conditioned stimulus, blocked the Food 2 at the second stage of the experiment and did not create an association between food 2 and an allergic reaction. This is consistent with the hypothesis and with previous research on Kamin blocking. Not surprisingly, the control group participants, who were not conditioned to Food 1, thought there was a greater probability of Food 2 causing an allergic reaction.
The results of this experiment is congruent with previous research on Kamin blocking (Marchant & Moore, 1973; C Sahley, Rudy, & Gelperin, 1981; Christie Sahley et al., 1981). Kamin blocking provides valuable insights into the mechanism of classical conditioning and how all stimulus are not similar in their effectiveness at creating a conditioned response. It has been established that Kamin blocking is an important learning mechanism in animals and can give valuable insights into information acquisition(Jones, Gray, & Hemsley, 1990). Studies have also shown that patients suffering from acute Schizophrenia often lose this ability(Jones, Gray, & Hemsley, 1992). It might be interesting to compare acquisition rates for different types of stimuli and find out how classical conditioning is affected by the nature of the stimuli. The concept of Kamin blocking can be further used for the betterment of education techniques.
References
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