Reinforcers Following Greater Effort are Preferred: A Within-Trial Contrast Effect

Psychologists who study human behavior often posit underlying mechanisms that are difficult to measure directly. And because humans are known to be complex organisms with complex motivational systems, researchers studying human behavior may avoid asking if there are simpler accounts of the behavior being studied. One such example is the phenomenon known as transposition. This phenomenon is familiar to musicians who after playing a tune in one key can seamlessly transpose the tune to a different key with no apparent change in the melody (the relations among the notes). A similar effect can be shown in rats, when after training them on a simultaneous light-gray (S+) versus dark-gray (S-) discrimination with responding to the light-gray reinforced, rats are tested with the light-gray stimulus and a still lighter-gray stimulus (Sn). In spite of the fact that responding to the S+ had a history of reinforcement and responding to the Sn had not, rats typically choose the Sn over the S+. That is, it appears that they learned to choose the lighter one during training and they continued to choose the lighter one on test trials. That is, it appears that they had learned the relation between the two training stimuli rather than their absolute properties. But Spence (1937) proposed that when organisms learn to respond to a stimulus for reinforcement, the tendency to respond generalizes to other similar stimuli (defining a gradient of stimulus generalization). Similarly, responding to the S- results in a gradient of inhibition around the value of the S- stimulus. According to Spence, it is the algebraic summation of those gradients at each point along the dimension that determines the strength of responding (the net response strength) at other points on the dimension (brightness in the example described). If one assumes that the gradients are convex (i.e., flatter near the training values) then the net gradient typically has its peak value not at the S+ but at a point away from the S+ in the direction away from the S-. This occurs because, given the presumed shape of the gradients, there would be a smaller decline in response strength as one begins to move away from the S+ than there would be a decline in inhibition at that point in the inhibitory gradient (see Spence, 1937). In this way, paradoxically, Spence's theory of learning about the absolute properties of a stimulus can account for an animal's choice of a novel stimulus, never seen before, over the S+ training value, and hence it can account for transposition without appealing to relational learning. Cognitive Dissonance An even more striking example of a presumably complex human behavior that is likely to be influenced by simpler behavioral processes is the supposed human motivation to reduce cognitive dissonance. Cognitive dissonance occurs when there is a discrepancy between one's beliefs and one's behavior. This can occur when one acts in a way that is inconsistent with the way one believes one should act. According to cognitive dissonance theory (Festinger, 1957), one should work to reduce the dissonance and if it is too late to avoid the behavior, one would modify one's beliefs to account for or justify one's behavior. Festinger and Carlsmith (1957) tested this theory by giving subjects a task considered to be boring and then asking them to tell a prospective subject that the task was interesting. In payment for this service, the experimenter would compensate them with a payment (the experimental manipulation) of either $1 or $20. But before carried out their assignment they were asked to fill out a questionnaire that included judgments about the task. Surprisingly, those subjects who were paid $1 judged the task to be more interesting than those who were paid $20. Festinger and Carlsmith explained the difference in terms of an attempt to reduce cognitive dissonance for the subjects paid only $1. For those subjects, the dissonance produced by having engaged in a boring task but having agreed to tell a potential subject that the task was interesting could not be resolved by appealing to the payment of $1. …