Absence of Anticipatory Contrast in Rats Trained on Multiple Schedules

Behavioral contrast and response-ratio sensitivity to reinforcement were compared in multiple schedules in which components alternated strictly or according to a pseudorandom sequence. Average component durations in the two regimes were always 60 s, and order of presentation of component alternation regimes was counterbalanced across subjects. In Part 1, the reinforcer rate in one component was reduced from 60 per hour to zero, while that in the other component was unchanged. Positive behavioral contrast occurred in the constant component in that response rates increased, but neither the reliability nor the magnitude of contrast was affected by the manner in which components alternated. Part 2 was similar, except that a number of different reinforcer rates were used in the varied component. Neither contrast nor sensitivity of response ratios to changes in reinforcer ratios depended on the regime of component alternation. Thus, the predictability in time of future reinforcement conditions, which is a feature of regular multiple scheduling, does not appear to be a determinant of multipleschedule performance.Key words: behavioral contrast, undermatching, component alternation, multiple schedules, key peck, pigeonsIn a multiple schedule of reinforcement, two or more components are presented successively, each in the presence of a distinctive stimulus. With pigeons as subjects, the stimulus may be a color or pattern that is projected onto a response key and remains present for some time period (known as the component duration). At the end of this period, the presentation of the component ends and is followed by a new component presentation. Experimental sessions usually involve a large number of presentations of two components, but three-and four-component arrangements are also sometimes used (e.g., Williams, 1979Williams, , 1981.Two aspects of performance in multiple schedules have been studied in detail, namely the relation between absolute response rates and reinforcer rates in components and the extent to which the distribution of responses between components varies with the distribution of reinforcers. Response rate in a component is clearly affected by the rate of reinforcement in the same component, and the phenomenon of behavioral contrast (Reynolds, 1961) reveals that it also depends on reinforcer rate in the alternate component. Behavioral contrast is found when one component is kept constant over several conditions in which the reinforcer rate in another component is varied. Contrast refers to a change in response rate during the constant component that is in the opposite direction from a reinforcer-rate manipulation in another component, and is generally taken as evidence that successively presented components of multiple schedules interact in determining response rate in any particular component (see, e.g., Herrnstein, 1970). The occurrence of contrast seems to depend on a change in relative reinforcer rate in the constant component (i.e., rate in the constant component relative to that in the varied on...

Section: Partsupporting

confidence: 79%

Contrast and Undermatching With Regular or Irregular Alternation of Components

McLean

Morritt

1994

“…One of the main problems is Williams ' (1979, 1981) finding that with pigeons as subjects, contrast in three-and fourcomponent multiple schedules is mostly a function of reinforcement conditions in the following component, whereas the reallocation hypothesis given above focuses on conditions in the previous component. Williams has suggested that there may be more than one behavioral process producing contrast (e.g., Williams, 1988Williams, , 1990Williams & Wixted, 1986)-one involving the following component and producing behavioral contrast and another involving the previous component and producing local or transient contrast. Reallocation could reasonably account only for the local contrast because it relies on behavior change in the previous component.…”

Section: Discussionmentioning

confidence: 99%

Contrast and Reallocation of Extraneous Reinforcers Between Multiple‐schedule Components

McLean

1992

Four pigeons responded in components of multiple schedules in which two responses were available and reinforced with food. Pecks on the left key ("main" key) were reinforced at a constant rate in one component and at a rate that varied over conditions in the other component. When reinforcer rate was varied, behavioral contrast occurred in the constant component. On the right key ("extra" key), five variable-interval schedules and one variable-ratio schedule, presented conjointly, arranged reinforcers for responses in all conditions. These conjoint schedules were common to both multiple-schedule components-rather than unique to particular components-and reinforcers from these schedules could therefore be arranged in one component and obtained during the other component. In this way, the additional reinforcers were analogous to the "extraneous" reinforcers thought to (Lander & Irwin, 1968;Reynolds, 1961 (1966).A good deal of research has attempted to determine what conditions affect the extent of behavioral contrast, and the focus of much of this work has been the manner in which the multiple schedules are arranged (for a review, see Williams, 1983). For example, studies have reported the effects of manipulating the time for which components are available on each presentation

“…In this case, no contrast, or non‐monotonic contrast effects, or the appearance of induction, may occur (Schwartz, ). When stimuli are less than optimal, as may be the case for rats with colored lights over levers, initial contrast but terminal induction (generalization from the following schedule) may occur (Williams, ). When the S + is remote, various effects can occur (e.g., Schwartz, ).…”

Section: The Types Of Contrastmentioning

confidence: 99%

A theory of behavioral contrast

Killeen

2014

This is the pre-peer reviewed version of the following article: Killeen, P. R. (2014). A theory of behavioral contrast. Journal of the Experimental Analysis ofBehavior, 102 (102), 3. doi: 10.1002/jeab.107 which has been published in final form at http://is.gd/3CK8y5 . Killeen@asu.eduRunning head: BEHAVIORAL CONTRAST 2 AbstractThe reinforcers that maintain target instrumental responses also reinforce other responses that compete with them for expression. This competition, and its imbalance at points of transition between different schedules of reinforcement, causes behavioral contrast. The imbalance is caused by differences in the rates at which different responses come under the control of component stimuli. A model for this theory of behavioral contrast is constructed by expanding the coupling coefficient of MPR (Killeen, 1994). The coupling coefficient gives the degree of association of a reinforcer with the target response relative to other competing responses.Competing responses, often identified as interim or adjunctive or superstitious behavior, are intrinsic to reinforcement schedules, especially interval schedules. In addition to that base-rate of competition, additional competing responses may spill over from the prior component, causing initial contrast; and they may be modulated by conditioned reinforcement or punishment from stimuli associated with subsequent component change, causing terminal contrast. A formalization of these hypotheses employed (a) a hysteresis model of off-target responses giving rise to initial contrast, and (b) a competing traces model of the suppression or enhancement of ongoing competitive responses by signals of following-schedule transition. The theory was applied to transient contrast, the following schedule effect, and the component duration effect. Keywords: Behavioral contrast, competing responses, MPRKilleen Page 3 A Theory of Behavioral ContrastAction at a distance is a bête noire for many scientists who spend their careers seeking mechanisms to mediate events that are disjoint in space or time. The young Newton disavowed recourse to unobservable hypothetical constructs (Westfall, 1971). But gravity epitomizes such a construct. In response to critics who noted the absence of mechanism in Principia, he simply asserted that he did not make hypotheses [about the mechanism]. He retreated, not from the construct, but from the demand to reify it. General relativity eventually provided a mechanism in the warping of space around massive bodies. Physicists discarded the luminiferous ether, but installed electromagnetic fields in its place. Feynman labored to rid physics of fields as anything other than book-keeping formulations (Mehra, 1994), but in the end he failed. The experimental validation of the Higgs field was recently greeted with universal applause. Nature, apparently, abhors a vacuum.Action at a distance is also a problem for behavioral psychologists. A modern cottage industry in our discipline is the study of delay discounting. Exactly how unexperienced slices of t...