The material to follow may be unfamiliar to some readers. Although there are two separate fields of comparative psychology, behaviorism and contemporary animal learning and conditioning, there are some who are understandably only familiar with the former. A problem that is beginning to be addressed is that most of the introductory comparative psychology literature has been written from the behaviorists’ perspective, leaving the more contemporary advancements largely undocumented at that level. *1

Between the 1930’s and 70’s behaviorism dominated. Behaviorist’s believed that the sole task for psychology was to study behavior in order to discover lawful relations between environmental events and actions; that is, to discover the laws of conditioning. They believed that environmental events, not the individual, caused a change in behavior, observable or otherwise. Therefore, a complete account of learning did not require mentalistic terms. Since they assumed environmental events caused behavior, it was thought states of mind could be bypassed in favor of observable stimulus-response explanations of behavior (see for example Skinner, 1950, 1974, 1977; Wessells, 1982).

Traditionally, behaviorists thought that all learning, for all animals, under all circumstances involved the direct establishment of stimulus-response connections. They argued that behavior could be understood without appeal to concepts such as knowledge, beliefs, intentions, or other cognitive influences. Subjects did not know why they were performing the response or what would happen when they responded. They did not acquire knowledge that a particular stimulus signaled an increase in the probability of a particular outcome or that a particular response would cause the occurrence of a particular outcome.

Behaviorists made the simplified assumption that the unobservable underlying psychological and neurological processes of learning corresponded isomorphically with observable events. For example, if in a particular stimulus situation, the data showed a change in behavior, behaviorists assumed that it was a corresponding stimulus-response connection that was strengthened. If the data showed a gradual strengthening of that behavior in a particular stimulus situation, it was assumed, based on the gradual strengthening, that subjects did not know they were learning. Instead, learning was thought to be automatic and unconscious, simply consisting of the gradual strengthening (stamping in) of stimulus-response connections (habits), rather than learning involving the acquisition of knowledge about the causal relationship between contingent events; that is, learning both about the probability of the outcome given the action and the probability of the outcome in the absence of the action. Additionally, since it was a change in behavior that was observed, it was assumed that it was a change in behavior that was learned, rather than the change in behavior reflecting a change in knowledge. Behaviorists thought stimulus-response connections were automatically and directly established either by simple contiguity between a stimulus and a response (classical conditioning) or by a combination of contiguity and the strengthening of a response through reinforcement and repetition (instrumental conditioning) (Bolles, 1975). Furthermore, it was assumed the presentation of an effective outcome that followed the stimulus and response served only to reinforce or strengthen the connection between the stimulus and response. The reinforcer supposedly did not enter into the associative structure; it functioned only as a catalyst to strengthen the link between the stimulus and response.

According to their beliefs, most of the experimental procedures behaviorists used to discover the laws of conditioning merely involved the simple pairing of two events. From experiments, the law of temporal contiguity was discovered, which ultimately became the most revered law of conditioning. All successful conditioning was assumed to be an automatic consequence of temporally pairing stimulus-response events with reinforcement. However, in the late 1960’s and early 1970’s a series of experiments, which had an important impact on how associative learning is now viewed, led theorists to question the importance of contiguity for successful conditioning. Kamin (1968, 1969), Rescorla (1966), and Revusky & Garcia (1970) showed that successful conditioning is not an automatic process of associating temporally paired events. These experiments, showing that the highly esteemed law of temporal contiguity was only a general law, led researchers to change their focus from trying to discover lawful relations between environmental events and actions to investigating how responding is affected by the interaction between multiple environmental events and reinforcement. Consequently, it became increasingly difficult to explain experimental evidence without the use of mentalistic terms. Thus, a radical change in experimental research and theories emerged.

Researchers now known that associative learning is comprised of a much richer array of processes than introductory textbooks typically offer, involving both classical and instrumental conditioning. By now, there is a good body of evidence establishing that conditioning does involve the acquisition of knowledge and beliefs about the world, which animals use to adaptively guide their choices and actions. During associative conditioning, animals are not learning a new response; they are learning that a particular stimulus signals an increase in the probability of a particular outcome or that a particular response causes a particular outcome. The response is a manifestation of the knowledge acquired about the causal relationship between the events the trainer has contingently arranged. Moreover, the establishment of a causal relationship, or successful conditioning, is not simply dependent on the number of times a particular stimulus or response and reinforcer have been paired together in a timely fashion. To distinguish a causal relationship from a mere correlative relationship, the course of conditioning is also affected by the subject’s prior learning experiences with that particular event and reinforcer, by the presence of other events signaling that particular reinforcer, and by the subject’s past experiences with those other events. Although contiguity is important, it is important to the learner only as an indicator of a possible causal relationship between the to-be-conditioned event and reinforcer. Since no to-be-conditioned event ever occurs in isolation of other events, the trainers to-be-conditioned event is only one among many other events that may or may not be the true signal or cause of the reinforcer. Thus, even if the reinforcer follows a to-be-conditioned event immediately after its occurrence, the subject will not necessarily associate the to-be-conditioned event with the reinforcer. For successful conditioning to occur, the to-be-conditioned stimulus or response must provide information about the occurrence of the reinforcer better than other events. Therefore, reinforcement contingencies are an important part of conditioning, for to arrange a reinforcement contingency is to arrange a causal relationship.

Since researchers started investigating how responding is affected by the interaction between multiple environmental events and reinforcement, it has been shown that conditioning cannot be reduced to a simple affair in which subjects can only register contiguously conjoined events. Leading scholars in the field of animal learning and conditioning now believe that animals register the antecedent events of an outcome and then, in an effort to reduce discrepancies, evaluate their predictive value relative to the other events that have been contiguously paired with that outcome, and then select the event that better predicts that outcome. In other words, animals attribute events of consequence to their most probable causes by associating selectively the better predictors of an outcome at the expense of poorer predictors. Selective or discriminative knowledge, comprising a broad range of environmental relations, is thought to be one of the main ways animals represent the structure of the world (Dickinson, 1980; Mackintosh, 1983; Rescorla, 1988).

In nature, it is often important for animals to discriminate the environmental stimuli that are the better predictors of biologically important events (are causally related) from those that are merely correlated with the outcome. When animals learn to discriminate between the events that better signal important outcomes from those that do not, they are learning to attend selectively to certain environmental stimuli. This voluntary selective attention is the result of the learned predictive relationship between stimuli and their outcomes. That is, animals learn to attend selectively to the stimulus events that predict or inform them of future events of importance and ignore less informative, redundant, or uninformative events. They learn both about the environmental stimulus events that better inform them of a valued outcome and about events that are less or uninformative. Selective attention is therefore an important determinant of discrimination learning.

A modern understanding about the ways in which animals select out stimulus information from among less informative events, and the ways in which that learning influences behavior, is considerably more important to discrimination training than traditional operant conditioning approaches that trainers may be more familiar with.


  1. By and large, detailed reviews of contemporary research and theories can only be found by searching through research or review articles. There are some books on the topic but most of them have not been written at an introductory level. Even at higher levels, texts reviewing the various learning theories tend to extensively cover the traditional theories while only minimally reviewing the disputing evidence and more contemporary theoretical explanations.


Bolles, R.C. (1975). Learning, motivation, and cognition. In W. K. Estes (Eds.), Handbook of learning and cognitive processes. Hillsdale, NJ: Lawrence Erlbaum Associates.

Dickinson, A. (1980). Contemporary animal learning theory.  Cambridge University Press, Cambridge.

Kamin, L. J. (1968). ‘Attention-like’ processes in classical conditioning. In M. R. Jones (Eds.), Miami symposium on the prediction of behavior: Aversive stimulation. Miami: University of Miami Press, 9-33.

Kamin, L. J. (1969). Predictability, surprise, attention, and conditioning. In B. B. Campbell and R. M. Church (Eds.), Punishment and aversive behavior. New York: Appleton-Century-Crofts, 279-296.

Mackintosh, N.J. (1983). Conditioning and associative learning. Oxford University Press, Oxford.

Rescorla, R. A. (1966). Predictability and number of pairings in Pavlovian fear conditioning. Psychonomic Science, 4, 383-384.

Rescorla, R.A. (1988). Pavlovian conditioning: It’s not what you think it is.  American Psychologist, 43, 151-160.

Revusky, S. and Garcia, J. (1970). Learned associations over long delays. In G. H. Bower (Eds.), The psychology of learning and motivation, 4, 1-84. Academic Press, New York.

Skinner, B.F. (1950). Are theories of learning necessary? Psychological Review, 57, 193-216.

Skinner, B.F. (1974). About behaviorism. New York: Knopf.

Skinner, B.F. (1977). Why I am not a cognitive psychologist. Behaviorism, 5, 1-10.

Wessells, M.G. (1982). A critique of Skinner’s views on the obstructive character of cognitive theories. Behaviorism, 10, 65-84.

Copyright © E Hale 2009.

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