Some weaknesses of a response-strength account of reinforcer effects

Evaluating functions of praise for children diagnosed with autism spectrum disorder

We assessed whether novel praise statements could be used to (a) maintain and increase responses with existing reinforcement histories and (b) teach a previously untaught response among children diagnosed with autism spectrum disorder across two experiments. During response-stimulus pairing, two responses resulted in preferred edibles but only one also produced a praise statement. In the absence of edibles, the response continuing to produce praise tended to persist more. Next, reversing the praise contingency tended to increase the other response. However, in no case did contingent delivery of those same praise statements result in the acquisition of untaught responses. These findings suggest that conditioning praise statements could serve different functions (antecedent or consequence) depending on the reinforcement history for particular responses.

Assessing human performance during contingency changes and extinction tests in reversal-learning tasks

Serial reversal-learning procedures are simple preparations that allow for a better understanding of how animals learn about environmental changes, including flexibly shifting responding to adapt to changing reinforcement contingencies. The present study examined serial reversal learning with humans by arranging both midsession and variable contingency reversals across two experiments. We also examined the effects of extinction by adding nonreinforced trials at the end of later sessions and provided the first evaluation of effects of win-stay/lose-shift versus counting strategies on accuracy and response latency of humans' reversal-learning performance. In each experiment, responding tracked contingency reversals, primarily with participants using either win-stay/lose-shift or counting strategies. Introducing variable reversal points in the second experiment resulted in near-exclusive win-stay/lose-shift responding among participants and eliminated counting of trials. Each experiment also revealed an immediate shift from S2 to S1 after experiencing extinction during the initial test trial, indicating resurgence of the initial response through a win-stay/lose-shift response pattern. Therefore, the present study replicates and extends prior findings of a win-stay/lose shift response pattern in situations of greater uncertainty. These findings suggest that differences in environmental certainty induce qualitatively different decision-making strategies.

Resistance to extinction versus extinction as discrimination

The hypothesis that response strength might be measured by persistence of responding in the face of extinction was discredited in the 1960s because experiments showed that responding persists longer following intermittent reinforcers than following continuous reinforcers. Instead, researchers proposed that the longer persistence following intermittent reinforcers arises because intermittent reinforcement more closely resembles extinction-a discrimination theory. Attention to resistance to extinction revived because one observation seemed to support the persistence hypothesis: Following training on a multiple schedule with unequal components, responding usually persisted longer in the formerly richer component than in the formerly lean component. This observation represents an anomaly, however, because results with single schedules and concurrent schedules contradict it. We suggest that the difference in results arises because the multiple-schedule procedure, while including extensive training on stimulus discrimination, includes no training on discrimination between food available and food unavailable, whereas comparable single- and concurrent-schedule procedures include such training with repeated extinction. In Experiment 1, we replicated the original result, and in Experiment 2 showed that when the multiple-schedule procedure includes training on food/no-food discrimination, extinction following multiple schedules contradicts behavioral momentum theory and agrees with the discrimination theory and research with single and concurrent schedules.

On the "Strength" of Behavior

The place of the concept of response strength in a natural science of behavior has been the subject of much debate. This article reconsiders the concept of response strength for reasons linked to the foundations of a natural science of behavior. The notion of response strength is implicit in many radical behaviorists' work. Palmer (2009) makes it explicit by applying the response strength concept to three levels: (1) overt behavior, (2) covert behavior, and (3) latent or potential behavior. We argue that the concept of response strength is superfluous in general, and an explication of the notion of giving causal status to nonobservable events like latent behavior or response strength is harmful to a scientific endeavor. Interpreting EEG recordings as indicators of changes in response strength runs the risk of reducing behavior to underlying mechanisms, regardless of whether such suggestions are accompanied by behavioral observations. Many radical behaviorists understand behavior as a discrete unit, inviting conceptual mistakes reflected in the notion of response strength. A molar view is suggested as an alternative that accounts for the temporally extended nature of behavior and avoids the perils of a response-strength based approach.

Stimulus control depends on the subjective value of the outcome

Stimuli that provide information about likely future reinforcers tend to shift behavior, provided a reliable relation between the stimulus and the reinforcer can be discriminated. Stimuli that are apparently more reliable exert greater control over behavior. We asked how the subjective value (measured in terms of preference) of reinforcers associated with stimuli influences stimulus control. Five pigeons worked on a concurrent chains procedure in which half of all trials ended in a smaller reinforcer sooner, and the other half in a larger reinforcer later. In Signaled trials, the color and flash duration on the keys in the initial link signaled the outcome of the trial. In Conflicting probe trials, the color and the flash duration signaled conflicting information about the outcome of the trial. Choice in Signaled trials shifted toward the signaled outcome, but was never exclusive. In Conflicting probe trials, control was divided idiosyncratically between the 2 stimulus dimensions, but still favored the outcome with the higher subjective value. Thus, stimulus control depends not only on the perceived reliability of stimuli, but also on the subjective value of the outcome.

Generalizing from the Past, Choosing the Future

Behavior in the present depends critically on experience in similar environments in the past. Such past experience may be important in controlling behavior not because it determines the strength of a behavior, but because it allows the structure of the current environment to be detected and used. We explore a prospective-control approach to understanding simple behavior. Under this approach, order in the environment allows even simple organisms to use their personal past to respond according to the likely future. The predicted future controls behavior, and past experience forms the building blocks of the predicted future. We explore how generalization affects the use of past experience to predict and respond to the future. First, we consider how generalization across various dimensions of an event determines the degree to which the structure of the environment exerts control over behavior. Next, we explore generalization from the past to the present as the method of deciding when, where, and what to do. This prospective-control approach is measurable and testable; it builds predictions from events that have already occurred, and assumes no agency. Under this prospective-control approach, generalization is fundamental to understanding both adaptive and maladaptive behavior.