Stimulus properties of conspecific behavior

Two experiments identified the conditions in which the behavior of one bird acquired discriminative control of the behavior of a second bird. The schedule-controlled behaviors of the “stimulus” bird were differentially correlated with the components of a multiple schedule according to which the pecking of an “experimental” bird produced food. In Experiment 1, three pairs of pigeons acquired a successive discrimination and two reversals with the conspecific stimuli. Experiment 2 included a control condition in which no systematic relationship existed between the conspecific stimuli and the component schedules. While differential responding during the components of the multiple schedule was again found when the conspecific stimuli were available, differential responding did not occur in the control condition. Test conditions included in the experiments indicated that (a) the differential responding was not dependent on the discriminative properties of reinforcement, (b) the pecking of the stimulus and experimental birds was temporally interrelated, (c) the visual conspecific stimuli were critical to the maintenance of the discrimination, and (d) the observed stimulus control immediately generalized to an unfamiliar conspecific.     

CORRESPONDENCE BETWEEN SINGLE VERSUS DAILY PREFERENCE ASSESSMENT OUTCOMES AND REINFORCER EFFICACY UNDER PROGRESSIVE‐RATIO SCHEDULES

Research has suggested that a daily multiple‐stimulus‐without‐replacement (MSWO) preference assessment may be more sensitive to changes in preference than other assessment formats, thereby resulting in greater correspondence with reinforcer efficacy over time ( DeLeon et al., 2001 ). However, most prior studies have measured reinforcer efficacy using rate of responding under single‐operant arrangements and dense schedules or under concurrent‐operants arrangements. An alternative measure of reinforcer efficacy involves the evaluation of responding under progressive‐ratio (PR) schedules. In the present study, 7 participants were given a single paired‐stimulus (PS) preference assessment followed by daily MSWO preference assessments. After each daily MSWO, participants responded for each stimulus on a PR schedule. The correspondence between break points and preferences, as assessed by the 2 assessment formats, was examined. Results demonstrated that both preference assessments did equally well at predicting reinforcer efficacy, although the PS more consistently identified the most effective reinforcer.     

Comparing the effects of static and dynamic signals during multiple schedules

The extent to which multiple schedules are an effective schedule thinning method following functional communication training (FCT) relies on the control the schedule-correlated stimuli exert over behavior. Thus, the stimuli used to signal the schedule in place (e.g., reinforcement and extinction) in a multiple schedule arrangement require special attention. To date, the majority of the research on multiple schedules has evaluated the use of different arbitrary signals as schedule-correlated stimuli (e.g., poster boards). These signals are considered static as they lack movement. More recently, some studies have successfully used dynamic signals, which include movement or animation, within multiple schedule arrangements. However, the extent to which one type of signal may result in faster stimulus control over behavior has not been evaluated. Thus, the purpose of this study was to compare the use of static and dynamic signals as schedule-correlated stimuli in multiple schedules used within the context of FCT. Four children diagnosed with autism spectrum disorder participated in the study. The results suggest that no differences in discriminated manding were observed for three out of four participants. Only dynamic signals resulted in discriminated manding for one participant.     

ASSESSMENT OF STEREOTYPIC AND SELF-INJURIOUS BEHAVIOR AS ADJUNCTIVE RESPONSES

Certain responses of both humans and nonhumans appear to be maintained indirectly by intermittent reinforcement schedules and have been referred to collectively as adjunctive behavior. Although basic research has examined adjunctive behavior extensively, relatively few studies have been conducted with humans, particularly those with developmental disabilities who often engage in frequent and varied stereotypic behavior. This study assessed possible adjunctive characteristics of self-injurious and stereotypic behaviors using a multielement design containing two types of control conditions. Four subjects who engaged in both self-injurious behavior and stereotypy participated after variables maintaining their self-injury were identified via functional analyses. Each day, subjects were exposed to three 15-min sessions in random order: (a) noncontingent presentation of food on a fixed-time schedule (e.g., FT 30 s), (b) a massed-reinforcement (food) control, and (c) a no-reinforcement control. A variety of fixed-time schedules were examined during different experimental phases. Results of this preliminary study suggested that self-injury was not induced by intermittent reinforcement schedules, whereas the stereotypic behavior of some individuals showed characteristics of adjunctive behavior. The importance of research on adjunctive behavior and suggestions for future studies are discussed.     

Chained and tandem scheduling with children

Children 4 to 7 yr in age were reinforced with trinkets and pennies on chained and tandem schedules. The schedules used were chain DRL FR, chain DRO FR, chain FI FR, tand FI FR, and tand DRO FR. Chain DRL FR and chain DRO FR schedules almost always produced strong schedule and stimulus control, but chain FI FR schedules rarely did if additional techniques were not used. Strong control was produced with chain FI FR schedules, however, if: (a) the FR component was increased in size; (b) schedule and stimulus control was first established with chain DRL FR or chain DRO FR schedules before shifting to the chain FI FR; or (c) an external clock was attached to the FI. Tand FI FR schedules never produced regular or repeatable patterns of responding when additional procedures were not used. Rate patterns resembling those of chain FI FR schedules were produced by tand FI FR schedules, however, if: (a) an external clock was attached to the FI component or (b) control was established by means of tand DRO FR schedules before the tand FI FR was used. Stimulus control was found to be exercised by specific visual stimuli, change of stimuli, and schedule order. Control exercised by schedule order was probably mediated by the child's own behavior which had assumed discriminative stimulus properties.     

Evaluating skills correlated with discriminated responding in multiple schedule arrangements

One potential solution for excessively high‐rate functional communication responses (FCR) is to establish stimulus control of the FCR through a multiple schedule. However, several studies have demonstrated difficulty with establishing discriminated responding across multiple schedule components. The primary aim of the current study was to evaluate how participants’ skills related to color discrimination may be related to the emergence of discriminated responding in a multiple schedule with colors as the schedule‐correlated stimuli. Three secondary aims of the current study were to evaluate: a) varied multiple schedule arrangements, b) if topographically dissimilar stimuli facilitated the emergence of discriminated responding, and c) if employing different colored stimuli across multiple schedule arrangements reduced the likelihood that discriminated responding emerged simultaneously across varied arrangements. Nine participants’ ability to match, select, tact, and respond intraverbally to colors was assessed, and 1 of 2 evaluations of multiple schedule arrangements were conducted. Results indicated that participants’ ability to select and tact colors was strongly correlated with the efficacy of standard multiple schedule arrangements. Additionally, multiple schedule arrangements employing topographically dissimilar stimuli were observed to be equally as effective as standard arrangements and the inclusion of different colored stimuli across arrangements did not reduce the likelihood that discriminated responding emerged simultaneously across all conditions, when it was observed to emerge at all.     

Evaluation of multiple schedules with naturally occurring and therapist‐arranged discriminative stimuli following functional communication training

Many studies have shown that (a) functional communication training (FCT) is effective for reducing problem behavior, and (b) multiple schedules can facilitate reinforcer schedule thinning during FCT. Most studies tha have used multiple schedules with FCT have included therapist‐arranged stimuli (e.g., colored cards) as the discriminative stimuli (S^Ds), but recently, researchers have evaluated similar multiple‐schedule training procedures with naturally occurring S^Ds (e.g., overt therapist behavior). The purposes of the current study were to compare the effects of arranged and naturally occurring S^Ds directly during (a) acquisition of discriminated functional communication responses (FCRs) and (b) generalization of discriminated FCRs when we introduced the multiple schedules in novel contexts in which the naturally occurring stimuli were either relatively easy or difficult to discriminate. Results showed that (a) 2 of 3 participants acquired discriminated responding of the FCR more rapidly with arranged than with naturally occurring stimuli, (b) 2 of 3 participants showed resurgence of problem behavior , and (c) 2 of 3 participants showed greater generalization of discriminated responding to novel contexts with arranged stimuli than with naturally occurring stimuli. We discuss these results relative to the conditions under which naturally occurring and arranged S^Ds may promote rapid and generalized treatment gains.     

Separating the reinforcing and discriminative properties of brief-stimulus presentations in second-order schedules.

Pigeons' responses were maintained under multiple schedules to study properties of briefly presented stimuli. Responses in one component produced food according to a second-order schedule with fixed-interval components in which food or a brief stimulus occurred with equal probability. In the second component responses produced only the brief stimulus under a fixed-ratio schedule. Under various conditions the brief stimulus in the first component was (a) paired with food, (b) not paired with food, (c) partially omitted, or (d) scheduled simultaneously with the second-order schedule under an independent variable-interval schedule. Paired and nonpaired brief stimuli maintained similar response patterning in the second-order schedule. However, only paired stimuli maintained responses in the second component. The data suggest that nonpaired brief stimuli engender response patterning in second-order schedules as a result of their discriminative properties. When the stimulus is paired with food, these discriminative properties sometime mask a reinforcement effect, and no change in response patterning is observed. When the discriminative properties of the brief stimulus are absent, the reinforcing effects of pairing the brief stimulus with food may be observed.     

Some determinants of remote behavioral history effects in humans

Undergraduates were exposed to a series of reinforcement schedules: first, to a fixed-ratio (FR) schedule in the presence of one stimulus and to a differential-reinforcement-of-low-rate (DRL) schedule in the presence of another (multiple FR DRL training), then to a fixed-interval (FI) schedule in the presence of a third stimulus (FI baseline), next to the FI schedule under the stimuli previously correlated with the FR and DRL schedules (multiple FI FI testing), and, finally, to a single session of the multiple FR DRL schedule again (multiple FR DRL testing). Response rates during the multiple FI FI schedule were higher under the former FR stimulus than under the former DRL stimulus. This effect of remote histories was prolonged when either the number of FI-baseline sessions was small or zero, or the time interval between the multiple FR DRL training and the multiple FI FI testing was short. Response rates under these two stimuli converged with continued exposure to the multiple FI FI schedule in most cases, but quickly differentiated when the schedule returned to the multiple FR DRL.     

Effects on concurrent performances of a stimulus correlated with reinforcer availability

A multiple schedule was arranged in which each component consisted of two, concurrent variable-interval schedules of reinforcement. A changeover-key procedure was used, and the components of the multiple schedule were distinguished (initially) by the color of the changeover key. During one component of the multiple schedule, the availability of a reinforcer arranged by one of the variable-interval schedules was marked by an exteroceptive stimulus, provided that that variable-interval schedule was not at the time assigned to the main key. During the other component of the multiple schedule, no reinforcer-correlated stimuli were ever presented. During the latter component of the multiple schedule, the distribution of responses and time for the concurrent variable-interval schedules suggested control by the distribution of reinforcements. During the former component, most main-key responses were emitted on the key in the presence of which reinforcer-correlated stimuli were presented. Changeover rate in the presence of that key color was depressed. The discriminative control over the changeover was easily established and was reversible.     

An analysis of contrast effects in multiple schedules

Some phenomena of behavioral contrast in multiple schedules are reviewed, and three accounts of contrast are considered. Rate changes within a constant schedule component (transient contrasts) are distinguished from rate changes across successive schedule cycles (sustained contrasts). Pigeons were exposed to a three-component multiple schedule, in which a stimulus correlated with a constant variable interval schedule of reinforcement was preceded by a stimulus correlated with more frequent variable interval reinforcement, or by an extinction stimulus. If the preceding stimulus was correlated with more frequent reinforcement, the response rate in the constant component was low and increased with time. If the preceding stimulus was correlated with extinction, the rate in the constant component was high and decreased with time. Similar transient contrasts were observed in a two-component multiple schedule with different variable interval schedules in the two components. The transient contrast effects in the three-component schedule were shown to depend on differential reinforcement frequency rather than differential response rate in the preceding component. Such transient contrasts were not sufficient to account for sustained contrast effects observed in these experiments. The relation of these findings to the concepts of excitation and inhibition is discussed.     

Reinforcement by an imprinting stimulus versus water on simple schedules in ducklings

Ducklings (5 to 28 days old) were trained to peck a pole on fixed-ratio, fixed-interval, and multiple schedules using brief presentation of an imprinting stimulus as the response-contingent event. Other ducklings of the same age were trained similarly except that reinforcement consisted of access to water. With water reinforcement the typical fixed-ratio (“break-run”), fixed-interval (“scallop”), and multiple schedule response patterns were readily established and consistently maintained. With the imprinting stimulus these schedule effects were inconsistent in some subjects and virtually nonexistent in others, despite extended training. Schedule control with the imprinting stimulus was not improved by the use of a reinforcement signaling procedure which enhances responding reinforced by electrical brain stimulation on intermittent schedules. However, the overall rates of responding and the extinction functions generated after reinforcement with water versus the imprinting stimulus were comparable. These findings imply that control by temporal and discriminative stimuli may be relatively weak when a young organism's behavior is reinforced by presentation of an imprinting stimulus.     

Discrimination of a response-independent component in a multiple schedule

Pigeons were trained to respond in non-differential reinforcement pre-discrimination training, with a multiple variable-interval 1-min variable-interval 1-min schedule. Each bird then received discrimination training with a multiple variable-interval 1-min variable-time 1-min schedule. Thus, discrimination training was between response-dependent (variable-interval) and response-independent (variable-time) schedules with the rate of reinforcement equated. In Experiment I, only three sessions of non-differential reinforcement preceded discrimination training and for half the birds, a 0° line was correlated with the response-dependent schedule; for the remaining birds the 0° line was correlated with the response-independent schedule. Post-discrimination gradients of excitatory stimulus control were obtained from the former group, while the latter group showed little evidence of post-discrimination stimulus control by the 0° line. Differential responding to the variable-time schedule was not accompanied by behavioral contrast to the variable-interval schedule. In Experiment II, 20 sessions of non-differential reinforcement preceded discrimination training and the 0° line was correlated with variable-time reinforcement for each bird. Differential responding to the 0° line was accompanied by negative induction to the variable-interval schedule and by inhibitory stimulus control about the 0° line during a post-discrimination generalization test.     

RESPONDING MAINTAINED BY INTERMITTENT REINFORCEMENT: IMPLICATIONS FOR THE USE OF EXTINCTION WITH PROBLEM BEHAVIOR IN CLINICAL SETTINGS

Results of basic research have demonstrated that behavior maintained on an intermittent schedule of reinforcement (INT) will be extinguished more slowly than behavior maintained on a continuous schedule (CRF). Although these findings suggest that problem behaviors may be difficult to treat with extinction if they have been maintained on INT rather than on CRF schedules, few applied studies have examined this phenomenon with human behavior in clinical settings. The purpose of this study was to determine whether problem behavior maintained on CRF schedules would be extinguished more rapidly than behavior maintained on INT schedules. Three individuals diagnosed with profound mental retardation participated after results of pretreatment functional analyses had identified the sources of reinforcement that were maintaining their self-injury, aggression, or disruption. Subjects were exposed to extinction following baseline conditions with CRF or INT schedules alternated within reversal or multielement designs. Results suggested that problem behaviors may not be more difficult to treat with extinction if they have been maintained on INT rather than CRF schedules. However, switching from an INT to a CRF schedule prior to extinction may lower the baseline response rate as well as the total number of responses exhibited during extinction.     

Effects of multiple versus chained schedules on stereotypy and item engagement

We evaluated rates of automatically reinforced stereotypy and item engagement for 2 children with autism under multiple and chained schedules in a multielement design. Each schedule included components during which stereotypy was blocked (S–) or allowed (S+), and we used colored cards as schedule‐correlated stimuli. We report rates of stereotypy and item engagement during S– and S+ components, as well as the percentage of component time that elapsed before the first instances of stereotypy and item engagement. We observed less stereotypy and more consistent item engagement during chained‐schedule sessions, and stimulus control of stereotypy and item engagement was established with the chained schedule. A subsequent concurrent‐chains analysis revealed participant preference for the chained schedule. These results highlight the importance of contingent access to stereotypy when therapists attempt to gain stimulus control of stereotypy and increase functional item engagement.     

Schedules using noxious stimuli. I. Multiple fixed-ratio and fixed-interval termination of schedule complexes

The termination of a schedule complex, comprising a stimulus in the presence of which brief presentations of electric shocks are scheduled, is a reinforcer. Conditions were studied under which schedule-controlled patterns of responding characteristic of fixed-interval, fixed-ratio, and multiple fixed-interval fixed-ratio schedules can be maintained in the squirrel monkey by terminating a schedule complex. The schedule of shock presentation was a critical determinant of the patterns of responding, especially under fixed-interval schedules of termination. The rates and patterns of responding under various schedules of termination of schedule complexes were generally akin to those maintained under comparable schedules of food presentation. The findings suggest a general similarity in the dynamic aspects of performances under schedules of schedule-complex termination and comparable schedules of food presentation. The schedule of reinforcement is more important than the nature of the reinforcer in the control of behavior.     

The effects of differential and lag reinforcement schedules on varied verbal responding by individuals with autism

Variability has been shown to be a reinforceable dimension of behavior. One procedure that has been demonstrated to increase variability in basic research is the lag reinforcement schedule. On this type of schedule, a response is reinforced if it differs from a specified number of previous responses. Lag schedules are rarely used, however, for increasing response variability in applied settings. The purpose of the present study was to investigate the effects of a lag schedule of differential reinforcement on varied and appropriate verbal responding to social questions by 3 males with autism. A reversal design with a multiple baseline across subjects was used to evaluate the effects of the lag schedule. During baseline, differential reinforcement of appropriate responding (DRA) resulted in little or no varied responding. During the intervention, a Lag 1 requirement was added to the DRA (Lag 1/DRA) resulting in an increase in the percentage of trials with varied and appropriate verbal responding for 2 of the 3 participants. In addition, an increase in the cumulative number of novel verbal responses was also observed for the same 2 participants. These results are discussed in terms of reinforcement schedules that support variability, generalization, and potential stimulus control over varied responding.     

The operant control of vocalization in the dog

Control over the vocal responses of three dogs was established using operant-conditioning procedures. Several points of interest were observed in the data. First, fixed-ratio schedules of reinforcement generated a vocal response topography which was similar in detail to that of a “motor” bar-nosing response. Second, vocal responding was brought under the control of external visual stimuli as a result of differential reinforcement. Third, good stimulus control was maintained on a multiple schedule containing a vocal-response component and a bar-response component. Fourth, the stimulus control on the multiple schedule transferred with minimal disruption to a chain schedule requiring a sequence of 10 bar responses followed by 10 vocal responses. Fifth, because vocal and bar responses are not mutually exclusive, concurrent responding tended to develop on the chain schedule.

These results were discussed with reference to the advisability of applying the terms operant and respondent to unconditioned behavior, and, particularly, to unconditioned verbal behavior.

     

Effects of conditioned reinforcement frequency in an intermittent free-feeding situation,

Key-pecking intermittently produced a set of brief exteroceptive stimulus changes under two-component multiple schedules of conditioned reinforcement. Throughout the study, free access to grain was concurrently provided on an intermittent basis via a variable-interval tape. Free food presentations scheduled by the tape were delivered if no peck had been emitted for 6 sec, and the brief stimulus changes produced by responding under the multiple schedules were those which accompanied food presentation. The second component of each multiple schedule was always associated with a 1-min, variable-interval schedule of conditioned reinforcement. The schedule associated with the first component was systematically varied and conditioned reinforcement was either absent (extinction) or programmed on a 1-, 3-, 6-, or 12-min variable-interval schedule. Under these conditions, rate of responding in the manipulated component decreased monotonically with a decrease in the frequency of conditioned reinforcement. In addition, contrast effects were often obtained in the constant, second component. These results are similar to those obtained with similar multiple schedules of primary reinforcement.     

Preference for less segmented fixed-time components in concurrent-chain schedules of reinforcement

A concurrent-chain procedure was used to examine choice between segmented and less segmented response-independent schedules of reinforcement. A pair of independent, concurrent variable-interval 60-s schedules were presented in the initial link, along with a 1.5-s changeover delay. A chained fixed-interval fixed-time and its corresponding tandem schedule constituted the terminal links. The length of the fixed-interval schedule in the terminal link was varied between 5 s and 30 s while that of the fixed-time schedule was kept at 5 s over conditions. The first components of both terminal-link schedules were accompanied by the same stimulus. Except in the baseline condition, the onset of the second component of the terminal-link chained schedule was accompanied by either a localized (key color) or a nonlocalized (dark houselight) stimulus change. Stimulus conditions were constant during the terminal-link tandem schedule. With three exceptions, pigeons demonstrated a slight preference for the tandem over the chained schedule in the terminal link. Furthermore, this preference varied inversely with the length of the first component. In general, these results are consistent with previous studies that reported an adverse effect on choice by segmenting an interval schedule into two or more components, but they are inconsistent with studies that reported preference for signaled over unsignaled delay of reinforcement.