Contrast and reallocation of extraneous reinforcers between multiple-schedule components

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 maintain behavior other than pecking in conventional multiple schedules. Response rate on the extra key did not change systematically over conditions in the constant component, and in the varied component extra responding was inversely related to main-key reinforcement. All subjects obtained more extra-key reinforcers in whichever component arranged fewer main-key reinforcers. Consistent with the theory that reallocation of extraneous reinforcers may cause behavioral contrast, absolute reinforcer rate for the extra key in the constant component was low in conditions that produced positive contrast on the main key and high in those that produced negative contrast. Also consistent with this theory, behavioral contrast was reduced in two conditions that canceled extra-key reinforcers that had been arranged but not obtained at the end of components. Thus, a constraint on reallocation markedly reduced the extent of contrast.     

Temporal constraint on choice: Sensitivity and bias in multiple schedules

In multiple schedules of reinforcement, ratios of responses in successive components are relatively insensitive to ratios of obtained reinforcers. An analysis is proposed that attributes changes in absolute response rates to concurrent interactions between programmed reinforcement and extraneous reinforcement in other components. The analysis predicts that ratios of responses in successive components vary with reinforcer ratios, qualified by a term describing the reinforcement context, that is, programmed and extraneous reinforcers. Two main predictions from the analysis were confirmed in an experiment in which pigeons' responses were reinforced in the components of a multiple schedule and analog extraneous reinforcement was scheduled for an alternative response in each component. Sensitivity of response and time ratios to reinforcer ratios in the multiple schedules varied as a function of the rate of extraneous reinforcers. Bias towards responding in one component of the multiple schedule varied as an inverse function of the ratios of extraneous reinforcer rate in the two components. The data from this and previous studies of multiple-concurrent performance were accurately predicted by our analysis and supported our contention that the allocation of behavior in multiple-schedule components depends on the relative values of concurrently-available reinforcers within each component.     

Undermatching and contrast within components of multiple schedules

Six multiple variable-interval schedules each comprised one variable-interval sixty second component and an alternated component which was varied. Four pigeons' responses were recorded in five successive subintervals of each component. Response rate changes across subintervals revealed instances of local contrast and small local induction effects in the changed component. In the constant component, smaller local contrast and larger local induction effects obtained. Accordingly, the magnitude of behavioral contrast, defined as an inverse relation between response rate in the constant component and reinforcement rate in the changed component, did not change reliably across subintervals of the constant component. Ratios of response rates in initial subintervals were highly sensitive to reinforcement ratios. Sensitivity decreased sharply over the first two-fifths of the components and remained constant for the remainder. The results demonstrated that changes in multiple schedule sensitivity are a function of time since the alternation of successive components.     

Mirrors, Clocks, Maps, and Music: A South African Response to Family Therapy Supervision/Training

Once upon a time a training unit embarked upon a Journey. The Journey was to encompass a year's training and supervision in family therapy. Bags were packed to the brim with theory and training methods. One day the Unit left the bags behind to see what would happen if they travelled light and let the students bring their own luggage to the examination. Students were expected to describe their relationships with the interviewed families, and their training through a story. The great exam day came. Inspired students used innovative ideas and metaphors to describe the Journey. This article tells the story about these stories and the Unit's learning from them.     

A front end to a theory of picture recognition

We describe the results of four picture-recognition memory experiments in which we systematically manipulated four variables: stimulus duration, stimulus contrast, the duration of a blank gap between successive presentations of the same stimulus, and the presence or absence of a noise mask that immediately followed stimulus offset. The patterns of obtained data confirmed a simple extension of a theory previously used to account for digit recall data. This theory consists of a low-pass linearfilter front end that generates a sensory response from the physical stimulus, followed by an informationsampling process whose instantaneous sampling rate is based in part on the sensory response magnitude. The data confirm both qualitative and quantitative theoretical predictions, some of which were previously untestable in digit recall tasks because of ceiling effects that were not present in our picturerecognition tasks. We describe the role of our theory within the broader family of picture-memory theories, and we briefly discuss our theory’s unification of two salient facets of visual behavior: information acquisition on the one hand, and phenomenological appearance on the other hand.     

Local contrast in behavior allocation during multiple-schedule components

Allocation of responses between two keys was studied during two alternating multiple-schedule components. Responses were recorded in successive quarters of each component. Variable-interval reinforcer schedules on the two keys were constant throughout the experiment for one (constant) component and were varied over conditions on one key for the other, producing changes in reinforcer ratios for the varied component. Behavior allocation for the first quarter of the constant component was inversely related to varied-component reinforcer ratios, a form of local contrast, but this relationship was not observed later in the component. During the first quarter of the varied component, slopes of matching lines were high and decreased later in the component. It is argued that this form of local contrast cannot be explained in terms of reallocation of extraneous reinforcers between components, and that the matching law for concurrent operants does not capture some sources of control over behavior allocation. A simple extension of the matching law is offered that adequately describes behavior changes during both components. A version of this formulation can predict contrast effects in absolute response rates.     

A comparison of flooding and thought stopping in the treatment of obsessional neurosis

Flooding in vivo and thought stopping were compared in patients with obsessional neurosis, in a cross-over design. It was hypothesized that the two techniques would have different effects on symptomatology. However, although both seemed to be effective treatments, there were no significant differences between them. Reasons for this finding are discussed. There was, however, a slight tendency for flooding to produce more overall improvement, and a greater reduction in avoidance behaviour. There was also a tendency for the first treatment to produce more effect. A worthwhile clinical finding was that a fair amount of improvement occurred after only eight out-patient sessions.     

Successive independence of multiple-schedule component performances

In three experiments, pigeons' responses were reinforced on two keys in each component of a series of multiple-schedule conditions. In each series, concurrent variable-interval schedules were constant in one component and were varied over conditions in the other component. In the first experiment both components arranged the same, constant total number of reinforcers, in the second the two components arranged constant but different totals, and in the third experiment the total was varied in one component and remained constant in the other. Relative reinforcer rate during the varied component was manipulated over conditions in all three experiments. In all these experiments, response and time allocation in the constant component were invariant when reinforcer ratios varied in the other component, demonstrating independence of behavior allocation in a multiple-schedule component from the relative reinforcer rate for the same alternatives in another component. In the two experiments which maintained constant reinforcer totals in components, sensitivity to reinforcement in the multiple schedules was the same as that in the concurrent schedules arranged during the varied component, with multiple-schedule bias in the experiment in which the totals were unequal.     

Comparison of reading and listening-reading techniques for administration of PIAT Reading Comprehension subtest: justification for the bypass approach

The Peabody Individual Achievement Test (PIAT) Reading Comprehension subtest was administered to a group of 23 learning disabled children in Grades 5 through 7 who had been classified by the clinical Lexical Paradigm as good readers or poor readers. Using standardized test administration, 14 poor readers scored substantially below the 9 good readers; however, when the child was allowed to listen and read silently while the test item was read aloud, poor readers showed marked improvement in performance compared to only moderate improvement shown by the good readers. This difference in improvement between the groups was significant and resulted in poor readers achieving performance similar to that of the good readers administered the test in the standard manner.     

Rapid acquisition in concurrent chains: evidence for a decision model

Pigeons' choice in concurrent chains can adapt to rapidly changing contingencies. Grace, Bragason, and McLean (2003) found that relative initial-link response rate was sensitive to the immediacy ratio in the current session when one of the terminal-link fixed-interval schedules was changed daily according to a pseudorandom binary sequence (e.g., Schofield & Davison, 1997). The present experiment tested whether the degree of variation in delays across sessions had any effect on acquisition rate in Grace et al.'s (2003) rapid-acquisition procedure. In one condition ("minimal variation"), the left terminal link was always fixed-interval 8 s and the right terminal link was either fixed-interval 4 s or fixed-interval 16 s. In the other condition ("maximal variation"), a unique pair of fixed-interval values was used in each session. Responding was sensitive to the current-session immediacy ratio in both conditions, but across subjects there was no systematic difference in sensitivity. These results challenge the view that initial-link responding in the rapid-acquisition procedure is determined by changes in the learned value of the terminal-link stimuli, and suggests instead that a process resembling categorical discrimination may control performance. A decision model based on the assumption that delays are categorized as short or long relative to the history of delays provided a good account of the data and shows promise in being able to explain other choice phenomena.