Contrast and reallocation of extraneous reinforcers as a function of component duration and baseline rate of reinforcement

Four pigeons responded on multiple schedules arranged on a “main” key in a two-key experimental chamber. A constant schedule component was alternated with another component that was varied over conditions. On an extra response key, conjoint schedules of reinforcement that operated in both components were arranged concurrently with the multiple schedule on the main key. On the main key, changes in reinforcement rate in the varied component were inversely related to changes in response rates in the constant component (behavioral contrast). On the extra key, some reinforcers were reallocated between components, depending on the schedules in effect on the main key in the varied component. In the varied component, the obtained rates of reinforcement on the extra key were inversely related to main-key reinforcement rate. In the constant component, extra-key reinforcer rates were positively related to main-key reinforcer rates obtained in the varied component, and were not a function of response rates on the extra key. In two comparisons, the rate at which components alternated and the value of the main-key schedule in the constant component were varied. Consistent with earlier work, long components reduced the extent of contrast. Reductions in contrast as a function of component duration were accompanied by similar reductions in the extent of reinforcer reallocation on the extra key. In the second comparison, lowering the rate of reinforcement in the constant component increased the rate at which extra-key reinforcers were obtained, reduced the extent of reinforcer reallocation, and reduced contrast. Overall, the results are consistent with the suggestion that some contrast effects are due to the changes in extraneous reinforcement during the constant component, and that manipulations of component duration, and manipulations of the rate of reinforcement in the constant component, affect contrast because they influence the extent of extraneous reinforcer real-location.     

Resistance to reinforcement change in multiple and concurrent schedules assessed in transition and at steady state

Behavioral momentum theory relates resistance to change of responding in a multiple-schedule component to the total reinforcement obtained in that component, regardless of how the reinforcers are produced. Four pigeons responded in a series of multiple-schedule conditions in which a variable-interval 40-s schedule arranged reinforcers for pecking in one component and a variable-interval 360-s schedule arranged them in the other. In addition, responses on a second key were reinforced according to variable-interval schedules that were equal in the two components. In different parts of the experiment, responding was disrupted by changing the rate of reinforcement on the second key or by delivering response-independent food during a blackout separating the two components. Consistent with momentum theory, responding on the first key in Part 1 changed more in the component with the lower reinforcement total when it was disrupted by changes in the rate of reinforcement on the second key. However, responding on the second key changed more in the component with the higher reinforcement total. In Parts 2 and 3, responding was disrupted with free food presented during intercomponent blackouts, with extinction (Part 2) or variable-interval 80-s reinforcement (Part 3) arranged on the second key. Here, resistance to change was greater for the component with greater overall reinforcement. Failures of momentum theory to predict short-term differences in resistance to change occurred with disruptors that caused greater change between steady states for the richer component. Consistency of effects across disruptors may yet be found if short-term effects of disruptors are assessed relative to the extent of change observed after prolonged exposure.     

Controlling the Ground Reaction Force During Lifting

The control of the ground reaction force vector relative to the center of gravity (CoG) was examined while subjects performed a back-lifting task. Six male subjects (aged 24.0 +/- 2.5 years) repeatedly lifted a barbell. A biomechanical analysis that used a linked segment model revealed that the summed rotations of body segments during lifting yielded a specific rate of change of the angular momentum of the entire body. This equaled the external moment provided by Fsubg; relative to CoG. This implies that multisegment movements involve control of the angular momentum of the entire body through an appropriately directed Fsubg;. Thus, in dynamic tasks Fsubg; is pointed away from rather than lined up with the CoG, as is the case in static tasks.     

Testing Two Theoretical Explanations for the Attraction-Enhancing Effects of Self-Disclosure

The study investigated the differential ability of similarity theory and social exchange theory to predict the effects of self-disclosure in a counseling versus a friendship encounter The participants were 80 undergraduates. A 2 (counseling or friendship) × 2 (positive or negative disclosure) × 2 (relevant or irrelevant disclosure) design was used in which participants rated the videotaped self-disclosure of an individual in an initial dyadic encounter. Unequivocal support was not obtained for either of the theories, but relationship context (counselor vs. peer) influenced the effects of disclosure as measured on counselor-peer and relationship characteristics. A unique feature of the study was the use of the Client Reactions System (CRS) to measure participants' immediate reactions to self-disclosure. The CRS demonstrated both relationship context and valence of disclosure (positive or negative) effects.     

Graphics in written directions: Appreciated by readers but not writers

This series of studies investigated the ability of literate adults to exploit communications options that are available to writers but have no counterpart in speech. Specifically it examined people's use of sketches when giving written directions to help a stranger cross town. When writing an informal letter to a friend most directions were given in prose paragraph style (Experiment 1). Almost no-one included a sketch, even if given a street map as an aid. Yet most subjects could draw adequate sketch maps (Experiment 2), and everyone said yes when asked whether they would include a sketch in a letter. So the previous choices were not constrained either by graphic skill or by judgements concerning the appropriateness of a sketch, When people were asked to 'design' the back page of a leaflet they still did not include a sketch (Experiment 3). Experiment 4 showed that any bias in the instructions was towards rather than against the use of sketches. The need to generate the sketch was removed in Experiment 5 where subjects composed the leaflet page from pre-formed sections that included alternative routes in both words and diagrams. Nearly all subjects now included a sketch in their directions. In case subjects previously, in haste, had not considered the possibility of including a sketch map, they were made aware of the drawing option by rating the usability of route information in a variety of communication styles immediately before writing their own directions (Experiment 6). People rated directions that included diagrams as significantly more usable, but still most subjects did not include a sketch in the directions they gave. So the communication styles that readers recognized as successful were not determining their choices as writers. It is suggested that, when giving written directions, inexperienced writers rely too heavily on how they would respond as speakers.