TEMPORAL CONTROL ON INTERVAL SCHEDULES: WHAT DETERMINES THE POSTREINFORCEMENT PAUSE?

On fixed-interval or response-initiated delay schedules of reinforcement, the average pause following food presentation is proportional to the interfood interval. Moreover, when a number of intervals of different durations occur in a programmed cyclic series, postreinforcement pauses track the changes in interval value. What controls the duration of postreinforcement pauses under these conditions? Staddon, Wynne, and Higa (1991), in their linear waiting model, propose control by the preceding interfood interval. Another possibility is that delay to reinforcement, signaled by a key peck and/or stimulus change, determines the subsequent pause. The experiments reported here examined the role of these two possible time markers by studying the performance of pigeons under a chained cyclic fixed-interval procedure. The data support the linear waiting model, but suggest that more than the immediately preceding interfood interval plays a role in temporal control.     

Delayed and current stimulus control in successive discriminations

In a successive discrimination in which successively alternating red and green hues signaled component variable-interval schedules, sensitivity of the ratio of responses in the two components to variation in the component reinforcer ratio decreased systematically during the course of the component. This decrease in stimulus control or discrimination over the course of the component was shown to be the result of delayed control of responding during the component by the stimulus transition between components. When the red–green stimulus transition was altered by interpolating a white stimulus at the end of each 60-s component, discrimination at the beginning of the component (measured by the power-function exponent for sensitivity to reinforcement) was reduced. Conditions with the white stimulus inserted in other quarters of the component indicated that the current discriminative stimulus exerts control over responding throughout the component, whereas during about the first half of the component, response differentials are influenced by the transition between discriminative stimuli.     

Exploring the set-theoretical structure of objects by additive trees

Arrangements of feature sets that have been proposed to represent qualitative and quantitative variation among objects are shown to generate identical sets of set-symmetric distances. The set-symmetric distances for these feature arrangements can be represented by path lengths in an additive linear tree. Imperfect versions of these feature arrangements are proposed, which also are indistinguishable by the set-symmetric distance model. The distances for the imperfect versions can be represented by path lengths in an additive imperfectly linear tree. When dissimilarities are defined by the more general contrast model and a constant may be added to proximity data, then for both the perfect and imperfect arrangements an additive tree analysis obtains a perfect fit with an imperfectly linear tree. However, in the case of the contrast model also the distinction between the perfect and imperfect arrangements disappears in that also for the perfect arrangements the resulting tree need no longer be linear.The author is grateful to Mathieu Koppen for detailed comments on an earlier version of this article.     

中国颜色体系研究

概述了用颜色立体模型表示物体颜色,并做定量表示的颜色体系研究的理论意义及应用价值。介绍了国际上影响较大的颜色体系理论和编制原则的特点。中国颜色体系研究是在对国际上其它颜色体系的理论分析和对颜色样品测试的基础上,确立其理论依据和编制原则,开展了中国人眼对明度、色调、彩度等间距排列的视觉评价实验,建立了中国颜色体系理论模型。同时研制出《中国颜色体系样册》。该项研究于１９９３年７月通过了国家自然科学基金委员会和中国科学院联合召开的成果鉴定会,并得到良好的评价,又于１９９４年６月通过国家标准审查。该项研究的完成和推广,不仅能为我国国民经济各部门的颜色控制、标定和交流提供科学的颜色定量手段,同时也是对实用色度学的发展和颜色标准化工作做了有益的工作,产生了积极的经济效益和社会效益。     

EFFECTS OF REINFORCEMENT HISTORY AND INSTRUCTIONS ON THE PERSISTENCE OF STUDENT ENGAGEMENT

We examined the effects of three reinforcement histories on the persistence of task engagement by 2 fourth-grade students using a partially counterbalanced ABCDBCD design. In each condition, an experimenter made four student contacts during the first 2 min of each session (reinforcement baseline), followed by an 8-min extinction period. The reinforcement history that contained an instructional control component produced the greatest persistence in student engagement. The applied relevance of instructional control is discussed.     

DIRECT AND COLLATERAL EFFECTS OF RESTRAINTS AND RESTRAINT FADING

Mechanical restraints are commonly used to reduce the risks associated with severe self-injurious behavior (SIB), but may result in movement restriction and adverse side effects (e.g., bone demineralization). Restraint fading may provide a method for decreasing SIB while increasing movement and reducing these side effects. In the current investigation, rigid arm sleeves and restraint fading (gradually reducing the rigidity of the sleeves) were used with 3 clients who engaged in hand-to-head SIB. Restraints and fading reduced the hand-to-head SIB of all clients. However, for 1 client, the addition of a water mist procedure further reduced SIB to near-zero levels. For a 2nd client, another form of SIB developed that was not prevented by the rigid sleeves. For a 3rd client, a topography of SIB that was not physically prevented by the rigid sleeves was also reduced when restraints and fading were introduced.     

Nodality effects during equivalence class formation: An extension to sight-word reading and concept development

Three students with moderate disabilities were taught to read and match-to-sample sight words comprising stimulus sets based upon the four food groups. We taught students conditional discriminations within four four-member sets using a single-sample/four-comparison procedure. Students were taught A-B, B-C, and C-D conditional discriminations for each of the four potential stimulus classes. Subsequent probes tested for relations based upon symmetry and one-node and two-node transitivity. The performances for all students indicated that symmetric relations emerged before one-node transitive relations, and that one-node transitive relations emerged before two-node transitive relations. These results are consistent with a pattern of responding, referred to as a "nodality effect," in which relations with fewer nodes are demonstrated prior to the demonstration of relations with a greater number of nodes. These results extend this area of research to sight-word reading for students with moderate disabilities.     

内部分配改革的职务评价技术探新

建立工资标准系统的关键是确定职务工资率。职务间可比价值成分变异越大,对确定职务工资率的贡献也越大。根据以上研究设想采用方差分析方法进行职务评价。评价步骤包括：职务描述;对职务要素作主成分分析;对职务样本作聚类分析和判别分析;通过方差分析为可比价值各成分建构权重系数ωｉ。ωｉ‘满足：（１）ωｉ≥０;（２）Σωｉ＝１;（３）ωｉ,间可直接比较;（４）ωｉ的大小与对应的可比价值成分变异一致。最后将职务评价值线性变换为工资率。在线性方程中配一个常数。和调节系数α以适合组织的管理约束条件。配合两个企业内部分配改革的研究结果显示了方差分析法的有效性和实用性。     

Stimulus control in the use of landmarks by pigeons in a touch-screen task

Pigeons were tested in a search task on the surface of a monitor on which their responses were registered by a touch-sensitive device. A graphic landmark array was presented consisting of a square outline (the frame) and a colored “landmark.” The unmarked goal, pecks at which produced reward, was located near the center of one edge of the frame, and the landmark was near it. The entire array was displaced without rotation on the monitor from trial to trial. On occasional no-reward tests, the following manipulations were made to the landmark array: (a) either the frame or the landmark was removed; (2) either one edge of the frame or the landmark was shifted; and (3) two landmarks were presented with or without the frame present. On these two-landmark tests, the frame, when present, defined which was the “correct” landmark. When the frame was absent, the “correct” landmark was arbitrarily determined. Results showed that pecks of 2 pigeons were controlled almost solely by the landmark, pecks of 3 were controlled primarily by the landmark but the frame could distinguish the correct landmark, and 1 bird's behavior was controlled primarily by the frame. Stimulus control in this search task is thus selective and differs across individuals. Comparisons to other search tasks and to other stimulus control experiments are made.     

Role of the striatal cholinergic system in the regulation of learned manipulation in rats

The experiments were performed on adult Wistar male rats trained to push with the forepaw on a fixed piston inside a narrow tube. It was found that after localized intracerebral injection of a cholinergic antagonist into the dorso-lateral (but not medial) neostriatum (i.e., the caudato-putamen) the behavioral performance requiring brief innate movements remained unchanged, but the performance requiring a prolonged pushing movement (> 50 msec) became disrupted. Microinjection of carbacholine (0.03-3 μ g/1 μ1) did not affect the performance of the acquired movements, whereas scopolamine (3 μ g/1 μ1) led to the significant decrease in pushing time. We conclude that changes in the state of the dorso-lateral neostriatal cholinergic system result only in disturbances of the sensory-controlled component of a complex instrumental movement. The 1994 Pavlovian Society Young Investigator Awardee was Nadezda Dubrovskaya, first author of this paper, which was presented at the annual meeting of the Pavlovian Society, July 3, 1994, in Prague, Czech Republic.