Choice, time allocation, and response rate during stimulus generalization

Six pigeons were trained to discriminate between two noise intensities using a procedure that assessed choice, time allocation, and response rate simultaneously and independently. Responses on the left or right key (R1 or R2) were respectively correct in the presence of two different intensities, S1 and S2. After a correct response, reinforcement became available for pecks on the center key. Reinforcement density for R1¦S1 relative to R2¦S2 was varied across experimental conditions. Generalization tests followed extensive training at each condition. As a function of stimulus intensity, proportions of initial choices of R2, of time spent in R2-initiated components, and of center-key responses emitted in R2-initiated components all yielded sigmoidal gradients of similar slope, which shifted slightly in location when relative reinforcement density changed. Changeovers were maximal where initial choice proportions approximated 0.5. Gradients relating the absolute number of center-key responses to stimulus intensity were also roughly sigmoidal, but were more sensitive to changes in reinforcement density. Gradients of momentary response rate also depended on reinforcement density. During training, large but transitory shifts in choice responding occurred when reinforcement density changed, while differences in momentary response rate developed slowly, suggesting separate control of choice and response rate by the contingencies of reinforcement.     

Clock control of human performance on avoidance and fixed-interval schedules

The avoidance and fixed-interval performances of human subjects were studied in two experiments. Addition of time-correlated stimuli (added clock) improved behavioral efficiency, since response rates decreased without decreases in reinforcement rates. Response-dependent display of the clock maintained a second, observing response and reductions in clock duration weakened such observing behavior. Generally, the reinforcing properties of the clock were more apparent with the avoidance than with the fixed-interval schedule, a finding attributed to temporal cues already provided by delivery of the fixed-interval reinforcers. Reduced rates of the main response when the clock was dependent on an observing response were more than offset by rates of the observing response in the majority of subjects. Thus, the results do not support an interpretation of the reinforcing properties of added clocks simply in terms of work reduction.     

A comparison of the key-peck and treadle-press operants in the pigeon: differential-reinforcement-of-low-rate schedule of reinforcement

Key pecking and treadle pressing in pigeons were compared under concurrent (key-treadle) and single-operant differential-reinforcement-of-low-rate schedules of food reinforcement ranging from 5 to 60 sec (concurrent procedure) or 5 to 120 sec (single-operant procedure). Under both procedures, the two operants followed the same general law: decreasing response rate and reinforcement rate and increasing number of responses per reinforcement as a function of increasing schedule interval. High correlations were found between key pecking and treadle pressing for the measures of response rate, reinforcement rate, and responses per reinforcement. Regression equations allowed the prediction of treadle pressing from key pecking. More bursting occurred in responding to the key, and key pecking showed a more precise temporal discrimination than treadle pressing. A test for sequential dependencies between key and treadle responses showed significant dependencies not only under the concurrent procedure but also in data created artificially by merging key and treadle sequences from different pigeons under the concurrent procedure and from the same pigeon under the single-operant procedure. It seems likely that the sequential dependencies found were due to the independent action of the schedule on each operant and that behavioral dependencies did not occur with the concurrent training procedure. The key-peck operant does not appear to have any special qualities that preclude its use in discovering general laws of behavior, at least under the differential-reinforcement-of-low-rate schedule. The usefulness of the key peck in other situations requires direct experimental study.     

Positive reinforcement and the elimination of reinforced responses

Key pecking was maintained on a fixed-interval schedule while either a differential-reinforcement-of-not-responding or a fixed-time schedule was imposed simultaneously. The lower the time parameter of the not-responding schedule, the lower was the response rate. Similar effects occurred with the fixed-time schedule, if the pigeons had experience with reinforcement for not responding. Otherwise the effects were less orderly, to the extent that rate could reach maximum with the lowest-valued fixed-time schedule. The not-responding and the response-independent schedules had similar effects on rate in experienced pigeons only when the time parameter or nominal frequency of food presentation was considered. When considered in terms of obtained frequency of food presentation, reinforcement of not responding produced larger decrements in rate than did the fixed-time schedule.     

Behavioral contrast as a function of the temporal location of reinforcement

Pigeons were trained on a multiple variable-interval variable-interval schedule of reinforcement. One component was then changed to a variation of a fixed-interval schedule in which the same rate of reinforcement was obtained as previously but the location of the reinforcer was fixed within the component. The effects of different temporal locations were compared. An increase in response rate for the unchanged variable-interval component (behavioral contrast) occurred when the reinforcer was located in the middle or at the end of the FI component, but response suppression occurred when it was located at the beginning of the component. The pattern of results cannot be explained by any previous theories of contrast. The overall response rates, and the pattern of local rates within the components, were consistent with the hypothesis that the major determinant of the contrast effect was the transition to a lower reinforcement rate following the unchanged component.     

Interactions in multiple schedules: the role of the stimulus-reinforcer contingency

In Experiments I and II, pigeons were exposed to single-key multiple schedules of response-independent and -dependent food presentation. Components were correlated with different keylights. When the rate of food presentation in the first component exceeded that in the second component, the local rate of key pecking was relatively high at onset of the first component. Overall rate in that component varied inversely with component duration and the rate of food presentation in the second component. When responding was maintained in the second component, the local rate of key pecking was relatively low at onset of that component. Overall rate in the second component varied directly with component duration and the rate of food presentation in that component. In Experiment III, pigeons were exposed to a two-key multiple schedule. Pecks on a constantly illuminated key produced food. Components were correlated with the color of a second key on which pecks had no scheduled consequences. The effects of component duration and rate of food presentation under the single-key response-dependent schedule were synthesized by combining response rates on each concurrently available key under the two-key procedure. The results support an account of multiple-schedule interactions in terms of the joint influence on responding of stimulus-reinforcer and response-reinforcer contingencies.     

Methodological improvements to a Procedure for Rapidly Establishing Steady-State Behavior

We performed three experiments to improve the quality and retention of data obtained from a Procedure for Rapidly Establishing Steady-State Behavior (PRESS-B; Klapes et al., 2020). In Experiment 1, 120 participants worked on nine concurrent random-interval random-interval (conc RI RI) schedules and were assigned to four conditions of varying changeover delay (COD) length. The 0.5-s COD condition group exhibited the fewest instances of exclusive reinforcer acquisition. Importantly, this group did not differ in generalized matching law (GML) fit quality from the other groups. In Experiment 2, 60 participants worked on nine conc RI RI schedules with a wider range of scheduled reinforcement rate ratios than was used in Experiment 1. Participants showed dramatic reductions in exclusive reinforcer acquisition. Experiment 3 entailed a replication of Experiment 2 wherein blackout periods were implemented between the schedule presentations and each schedule remained in operation until at least one reinforcer was acquired on each alternative. GML fit quality was slightly more consistent in Experiment 3 than in the previous experiments. Thus, these results suggest that future PRESS-B studies should implement a shorter COD, a wider and richer scheduled reinforcement rate ratio range, and brief blackouts between schedule presentations for optimal data quality and retention.     

Social preference in rats

Rats were given repeated choices between social and nonsocial outcomes, and between familiar and unfamiliar social outcomes. Lever presses on either of 2 levers in the middle chamber of a 3-chamber apparatus opened a door adjacent to the lever, permitting 45-s access to social interaction with the rat in the chosen side chamber. In Experiment 1, rats preferred (a) social over nonsocial options, choosing their cagemate rat over an empty chamber, and (b) an unfamiliar over a familiar rat, choosing a non-cagemate over their cagemate. These findings were replicated in Experiment 2 with 2 different non-cagemate rats. Rats preferred both non-cagemate rats to a similar degree when pitted against their cagemate, but were indifferent when the 2 non-cagemates were pitted against each other. Similar preference for social over nonsocial and non-cagemate over cagemate was seen in Experiment 3, with new non-cagemate rats introduced after every third session. Response rates (for both cagemate and non-cagemate rats) were elevated under conditions of nonsocial (isolated) housing compared to conditions of social (paired) housing, demonstrating a social deprivation effect. Together, the experiments contribute to an experimental analysis of social preference within a social reinforcement framework, drawing on methods with proven efficacy in the analysis of reinforcement more generally.     

A comparison of accumulated and distributed reinforcement periods with children exhibiting escape-maintained problem behavior

Differential reinforcement is a common treatment for escape-maintained problem behavior in which compliance is reinforced on a fixed-ratio (FR) 1 schedule with brief access to positive and/or negative reinforcement. Recent research suggests some individuals prefer to complete longer work requirements culminating in prolonged (i.e. accumulated) reinforcement periods relative to brief (i.e. distributed) periods, but prolonged work exposure may evoke problem behavior and prevent compliance from contacting reinforcement when treating escape-maintained problem behavior. We exposed 3 children with escape-maintained problem behavior to both distributed (FR 1 resulting in 30 s of reinforcement) and accumulated (FR 15 resulting in 7.5 min of reinforcement) arrangements to compare their efficacy in maintaining low levels of problem behavior. We then assessed participants' preferences for these conditions in a concurrent-chains arrangement. Accumulated-reinforcement arrangements did not occasion additional problem behavior, but rather resulted in consistently lower levels of problem behavior for 2 of 3 participants. Participants demonstrated idiosyncratic preferences.     

留守初中生同伴侵害与攻击性的关系:链式多重中介模型

为探究留守初中生同伴侵害与攻击性的关系机制,通过构建链式多重中介模型,考察歧视知觉、孤独感和心理韧性在二者关系中的多重中介效应。采用问卷调查法对519名留守初中生进行调查,结果显示：（1）留守初中生同伴侵害的发生率为96.3%,具有普遍性;（2）留守初中生同伴侵害、歧视知觉、孤独感、心理韧性与攻击性之间均呈显著相关;（3）留守初中生的歧视知觉、孤独感和心理韧性在其同伴侵害与攻击性的关系中具有链式多重中介作用;（4）同伴侵害与攻击性关系模型具有一定稳定性,同时在是否留守及单亲与双亲外出留守初中生群体中存在显著差异。研究结果揭示了同伴侵害与攻击性的关系机制,可为探索留守初中生不良同伴关系的教育策略提供参考。