Generalization

Description of the Strategy

Generalization occurs when behavior in one environment changes by virtue of reinforcement contingencies imposed on that behavior in a second environment that has stimuli in common with the first. As a laboratory example, if pecking a green disk by a pigeon is followed by food, pecking will also increase somewhat if the disk becomes blue or yellow. Pecking the blue or yellow disk exemplifies generalization along the physical dimension of wavelength (color). Similarly, if saying “ball” by a child is praised when a red ball rolls across the floor, saying “ball” may also occur when a yellow ball is presented or, perhaps, even when an object such as a candle rolls across the floor. The shape of the ball provides the common stimuli in the first case, the movement of the object in the second. In either case, the environmental guidance of behavior is altered in an environment that differs in some way from the one in which the behavior was conditioned. Generalization can occur following conditioning with either a classical or an operant procedure.

Here, we focus on two issues: the variables that affect the extent of generalization and the behavioral processes involved in generalization. The extent of generalization is affected by the physical similarity between environments and by the history of the organism. The history includes both the history of the species of which the organism is a member (natural selection) and the history of the individual (selection by reinforcement). As an example of the first, consider food reinforcement for pecking a green disk when a medium-pitched tone is also present. If the color of the disk is then changed but the pitch of the tone remains the same, pecking declines progressively as the color departs from green. However, if the pigeon is tested when the pitch of the tone changes but the color of the disk remains green, pecking is unchanged. Generalization occurred along the color dimension but not the pitch dimension, although pecking was reinforced as frequently during the medium-pitched tone as during the green disk. This difference occurs in part because pigeons have an evolutionary history of natural selection in which visual stimuli reliably guided consummatory behavior but auditory stimuli did not. With a nocturnal animal for which consummatory behavior has been guided over evolutionary time by auditory instead of visual stimuli, the opposite could occur.

The most important determinant of generalization is the history of the individual organism. As a laboratory example, if pecking a green disk is reinforced during a medium-pitched tone but not when the tone is absent and the disk remains green, generalization now occurs along the pitch dimension and less so along the color dimension. Differential reinforcement of responding along the tone dimension causes the history of selection by reinforcement to override the history of natural selection. Stated broadly, if behavior has different consequences in different environments, then the strength of responding varies systematically as the environment departs from the environment in which the behavior was reinforced. That is, stimulus generalization occurs.

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