Classical Conditioning
In the previous part, we discussed behaviourism and gave an outlook of classical conditioning. Today, we are going to talk in detail on classical conditioning.
In the early 1900s, Russian physiologist Ivan Pavlov conducted a series of salivation experiments in dogs in order to better understand the nature of digestion. Pavlov devoted a significant portion of his later years to a systematic study of the learning process that he had inadvertently stumbled upon, and he eventually summarised his research in his book Conditioned Reflexes.
The phenomenon observed by Pavlov is now known as classical conditioning. Let us examine the three steps in Pavlov's experiment in the same manner as Pavlov:
1. A neutral stimulus (NS) is identified—a stimulus to which the organism has no discernible response. The bell was initially a neutral stimulus that did not elicit a salivation response in Pavlov's dogs.
2.The neutral stimulus is presented immediately before another stimulus that elicits a response. This second stimulus is referred to as an unconditioned stimulus (UCS), and the organism's response to it is referred to as an unconditioned response (UCR), because the organism responds to the stimulus unconditionally, without having to learn to do so. Meat powder was an unconditioned stimulus to which Pavlov's dogs responded with the unconditioned response of salivation.
3. When combined with an unconditioned stimulus, the previously neutral stimulus elicits a response and is thus no longer "neutral." The NS has evolved into a conditioned stimulus (CS) in response to which the organism has learned a conditioned response (CR).
Pavlov's classical conditioning research continued long after these initial experiments, and many of his findings have been replicated with different responses and in different species, including humans.
Let's look more closely at classical conditioning and some examples of how it might occur in human learning.
The Classical Conditioning Model
Classical conditioning has been demonstrated in a variety of species, including newborn human infants, human foetuses still in the womb, laboratory rats, and rainbow trout. Classical conditioning is clearly applicable throughout the animal kingdom.
Classical conditioning, as demonstrated by Pavlov's experiments, occurs when two stimuli are presented at roughly the same time. An unconditioned stimulus is one of these stimuli: It has previously been demonstrated that it elicits an unconditioned response. Through its association with the unconditioned stimulus, the second stimulus begins to elicit a response as well: it becomes a conditioned stimulus that results in a conditioned response. Conditioning occurs quickly in many cases; it is not uncommon for an organism to show a conditioned response after only five or six pairings of the two stimuli, and sometimes after only one pairing (Rescorla, 1988).
Common Phenomena in Classical Conditioning
Pavlov and other behaviourists described a variety of classical conditioning phenomena. We'll look at a few of them here: associative bias, contingency importance, extinction, spontaneous recovery, generalisation, stimulus discrimination, higher-order conditioning, and sensory preconditioning.
Associative Bias
The characteristics of the potential conditioned stimulus influence the extent to which conditioning occurs. The more noticeable (salient) a neutral stimulus is—the more bright, loud, or otherwise intense it is—the more likely it is to become a conditioned stimulus when combined with an unconditioned stimulus (Rachlin, 1991; B. Schwartz & Reisberg, 1991). Furthermore, some stimuli are more likely than others to become associated with specific unconditioned stimuli; for example, food is more likely than, say, a flash of light or the sound of a tuning fork to become a conditioned stimulus associated with nausea (a UCS). In other words, the phenomenon, associative bias, is the associations formed between certain stimuli are more likely than associations formed between others.
Importance of Contingency
When the focus of the study is on stimuli and responses, learning processes can be studied most objectively. Behaviourists believe that psychologists must study learning through objective scientific inquiry, much like chemists and physicists study physical phenomena. Psychologists can maintain objectivity by focusing on two things they can observe and measure—specifically, stimuli in the environment and responses that organisms make to those stimuli. Behaviourist learning principles frequently describe a relationship between a stimulus (S) and a response (R); thus, behaviourism is also known as S-R psychology.
Extinction
Pavlov discovered that repeatedly presenting the conditioned stimulus without the unconditioned stimulus resulted in weaker and weaker conditioned responses. The dogs eventually stopped salivating at the sound of the bell. In other words, the conditioned response vanished. Pavlov referred to this phenomenon as extinction.
Generalization
Little Albert became afraid of a rabbit, a dog, a white fur coat, cotton wool, and a fuzzy-bearded Santa Claus mask after being conditioned to fear a white rat. Generalization occurs when learners respond to non-conditioned stimuli in the same way that they respond to conditioned stimuli. The greater the similarity of a stimulus to the conditioned stimulus, the greater the likelihood of generalisation.
Stimulus Discrimination
Pavlov discovered that if he trained a dog to salivate in response to a high-pitched tone, the dog would generalise that response to a low-pitched tone. Pavlov repeatedly presented the high tone with meat powder and the low tone without meat to teach the dog the difference between the two tones. The dog eventually learned to salivate only at the high tone after several such presentations of the two tones. Differentiation between the two tones had occurred, according to Pavlov's terminology. This phenomenon is now more commonly referred to by psychologists as stimulus discrimination.
Higher Order Conditioning
Conditioned stimulus-response associations can sometimes overlap. For example, if Pavlov conditioned a dog to salivate at the sound of a bell and then presented the bell with another neutral stimulus—say, a flash of light that had never been associated with meat—that neutral stimulus would begin to elicit a salivation response as well. This is referred to as second-order conditioning or, more broadly, higher-order conditioning.
Sensory Preconditioning
Sensory preconditioning is similar to higher-order conditioning in that each stimulus-response association builds on the previous one, but the steps are performed in a different order. Let us return once more to Pavlov's poor, exploited dogs. Assume we first show the sound of a bell and a flash of light at the same time. The bell is then paired with meat powder. The dogs salivate not only in response to the sound of a bell, but also in response to a flash of light.
To Conclude
Classical conditioning is most likely to occur when the conditioned stimulus is presented just before the unconditioned stimulus (perhaps by half a second). As a result, some psychologists define classical conditioning as a type of signal learning. The conditioned stimulus, by being presented first, serves as a signal that the unconditioned stimulus is on its way, much like Pavlov's dogs might have learned that the sound of a bell indicated that yummy meat powder was on its way.
Classical conditioning is typically associated with the acquisition of involuntary responses—responses over which the learner has no control. When we say that a stimulus elicits a response, we mean that the stimulus causes a response without the learner having much control over the event happening.