The process whereby an organism interacts with its environment and becomes changed by the experience so that its subsequent behaviour is modified. It will be noted that this definition encompasses a wider range of phenomena than those that would usually be considered as instances of learning by the layperson. For the latter, the term is restricted for the most part to the processes involved in the explicit ACQUISITION of new information (as when a new academic subject is mastered) or of a new skill (as in learning to read or to drive a car). These are clearly instances of learning in terms of the definition just offered, but so is the following. If you leave the room in which you now are and return to it an hour later, your behaviour on returning will be different, because of what you have experienced here on the present visit and also because of what you experienced in the intervening hour. The ways in which your behaviour is changed may not be very dramatic—perhaps you will simply be better able to find this book on the shelf and will want to look up a different entry because of something asked of you while you were away—but these behavioural changes none the less constitute examples of learning in terms of our definition. It is because they have generally adopted this wider interpretation of the concept that psychologists have historically devoted so much effort to the study of the learning process: the way in which behaviour is modified by interaction with the environment is a central topic of psychology.
It is normal to distinguish different types of learning and many different categorizations have been offered. Sometimes distinctions are drawn for immediate practical reasons—for some purposes it may be useful to distinguish motor skill learning from other forms of learning.
For other purposes we might want to identify a separate category of rewarded learning as distinct from that generated by the attempt to avoid aversive events; and so on. Such descriptive classifications are not problematic but attempts to distinguish different types of learning that differ at a more fundamental level (for instance, in terms of the mechanisms that underlie them) have provoked considerable debate. Thus, for example, some theorists have maintained that PAVLOVIAN CONDITIONING and INSTRUMENTAL CONDITIONING involve quite different processes, whereas other have emphasized what they take to be important similarities between the two. (The modern consensus is that both should be viewed as versions of ASSOCIATIVE LEARNING, differing principally only in the nature of the events that enter into association.) Again, some have wanted to make a distinction between learning based on the cumulative effect of a series of training trials (as when a rat slowly acquires the behaviour of pressing a lever to obtain food) from behaviour patterns that are suddenly acquired (as when an ape in a flash of ‘insight’ piles boxes together to get to an item of food otherwise out of reach). But others have pointed out that the behaviour of the ape can be shown to depend on its having had, earlier in its life, protracted experience of manipulating objects such as boxes and of the consequences of these actions and to this extent the ape’s behaviour too is a product of the cumulative effect of a series of (informal) training trials.
The distinction that seems most likely to survive is that between associative and non-associative learning. The former depends on the animal having experience of paired events and the change in behaviour produced by this experience is the consequence of the formation of some link between the central representations of these events. (Pavlovian conditioning constitutes the paradigm case.) There are, however, a number of examples of learning in which the animal is exposed not to a pairing but to just a single event, thus precluding any simple explanation in terms of the associative mechanism. Examples include HABITUATION (the waning of the unconditioned response initially evoked by a stimulus as a consequence of repeated presentations of that stimulus); IMPRINTING (the acquisition by a young animal of filial responses to a conspicuous object experienced early in life); PERCEPTUAL LEARNING (enhancement of the discriminability of a stimulus as a result of exposure to that stimulus). It should be noted, however, that these instances are defined solely by exclusion (that is, simply as not being associative) and thus there is no guarantee that all are products of a common underlying mechanism. Closer examination could reveal that a distinctively different learning process operates in each case.
GEOFFREY HALL
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