![]() ![]() Environmental stimuli are generally perceived simultaneously with or immediately after the events that cause them. This captures Nature’s rule of cause and effect. Contiguity refers to the property of the stimuli occurring coincidentally, that is overlapping in time or one immediately after the other in time. I bring up these examples as indications of the robustness of associative memory, but with the interesting twist that as with all robust systems there is an attendant possibility of error-proneness.Īgainst this backdrop it is then interesting to consider that associative learning depends on two attributes of the environmental stimuli- contiguity and contingency. Presumably what has happened is that early on in the training, the animal has erroneously associated some movement on their part with the food reward, and formed a lasting but inaccurate memory that executing the movement is necessary to receive the reward. Regardless of the terminology, it is clear that these are examples of associative learning gone awry. Skinner termed these behaviors “superstitious” behaviors, a somewhat loaded term that is anthropomorphic, but not without appeal. Skinner recorded several similar circumstances in training pigeons in associative learning tasks, where in some cases elaborate but unnecessary motor patterns were executed before the animal pecked an object to receive a food reward. Of course, in reality the hand movement was entirely superfluous to the task and the reward delivery. However, the animal also “learned” that it was necessary to wave his hand in an idiosyncratic way in order for the food reward to be delivered. For example, one of my colleagues who works with Macaque monkeys had a monkey who learned that certain visual stimuli predicted the subsequent arrival of a food reward. Numerous examples exist in the literature and anecdotally of animals having mislearned associations. However, this is not to say that associative learning is flawless. This is one significant factor in the popularity of studying associative learning experimentally-the learned behaviors are observable, relatively rapidly acquired, and reliably expressed. Generally associative learning is quite reliable-obviously the accuracy of storing cause-and-effect relationships is of paramount importance and has been selected for evolutionarily. Thus, nervous systems of all sorts have evolved to the best of their capacity sophisticated and robust circuit, cellular, and molecular mechanisms to encode these types of information. The importance of this last point cannot be overstated! Nature has selected for a robust capacity of nervous systems to accurately reflect one of the principal physical laws that govern the real world: cause and effect. The stable formation of a memory trace, such that an accurate record of cause-and-effect relationships is available for future reference, provides such a pronounced competitive advantage that this form of learning is typically quite vigorous. Stated another way, associative learning allows the neural encoding of cause-and-effect relationships. This type of learning is profoundly important for survival in any natural environment, and for this reason has been robustly selected for in animal evolution. In associative learning an animal learns the predictive value of one stimulus for another, in Pavlov’s example the reliability of a tone for predicting a subsequent food presentation. Repeated pairings of an auditory cue with food causes the animal to learn the predictive value of one for the other. Pavlovian associative conditioning of the canine salivary response. The bell-elicited salivation was termed the conditioned response, and correspondingly the bell tone was termed the conditioned stimulus ( Figure 13).įigure 13. Over time the dog would form an association between the bell and the food, and Pavlov found that the bell alone would ultimately cause a salivatory response just like the food did. Pavlov’s breakthrough realization, which he subsequently rigorously documented and studied, was that he could train dogs to associate a neutral stimulus, such as the ringing of a bell, with the food stimulus. This is a natural response, of course, and this salivation is referred to as the unconditioned response, and correspondingly the food stimulus is referred to as the unconditioned stimulus. Pavlov knew, as does anyone that has ever owned a dog, that when a dog is presented with a food stimulus a strong salivatory response is elicited (see Figure 13). Pavlov and his co-workers studied associative conditioning of the salivary response of dogs-studies indeed so classic that the terms classical conditioning and Pavlovian conditioning are now used synonymously with associative conditioning. An important set of nomenclature in this area arose out of the pioneering work of Ivan Pavlov ( Figure 12). ![]()
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