Partial visual feedback and spatial end-point accuracy of discrete aiming movements

Five experiments are reported in which the effect of partial visual feedback on the accuracy of discrete target aiming was investigated. Visual feedback was manipulated through a spectacle-mounted liquid-crystal tachistoscope. The length of the visual feedback interval was varied as a percentage of the instructed movement time. In Experiment 1, the length of the vision interval was manipulated symmetrically at the beginning- and end-phase of the movement, whereas in the remaining experiments, the vision time was varied with respect to the end-phase only. The variations at the end were examined for different distances (Experiment 2), different movement speeds at the same distance (Experiment 3), and in small interstep intervals (Experiment 4). A vision time of more than 150 ms at the end-phase of the movement enhanced aiming performance in all experiments. Longer vision times monotonously improved aiming accuracy; the fifth experiment showed that a vision time of about 275 ms was sufficient for near-perfect aiming. Furthermore, the significance of vision during the first phase of a movement was demonstrated again. The results of the five experiments pointed to shorter visuomotor processing times. To explain the beneficial effects of short vision times for aiming accuracy, we propose a model of visuomotor processing that is based on the stochastic optimized submovement model of Meyer, Abrams, Kornblum, Wright, and Smith (1988).     

Integrating Qualitative and Quantitative Research Methods: A Research Model

A historical antagonism between proponents of qualitative methods and quantitative methods has prevented recognition of the benefits to be gained by employing both methods (that is, a multi-method approach) during the same study or program of studies. Increasingly, family therapy researchers have begun to recognize the value of a multi-method approach in bridging the current gaps among theory, research, and practice. However, current writings have yet to move beyond the discussion stage. This article proposes a bidirectional continuum that includes both qualitative and quantitative methods. An ethnographic content analysis approach is presented to illustrate the procedural stages of this continuum. The article ends with a discussion of the challenges in carrying out a bidirectional, multi-method approach and the potential contributions that an integrative research methodology will give both researchers and clinicians.     

Decision-making incapacity among nursing home residents: results from the 1987 NMES survey. National Medical Expenditure Survey

Recent legislative and regulatory developments have focused attention on older adults' capacity for involvement in health care decision-making. The Omnibus Budget Reconciliation Act of 1987 (OBRA 87) focused attention on the rights of nursing home residents to be involved in health care decision-making to the fullest extent possible. This article uses data from the 1987 National Medical Expenditure Survey (NMES) to examine rates of incapacity for health care decision-making among nursing home residents. Elements of the Oklahoma statute were used to operationalize decision-making incapacity: disability or disorder, difficulty in decision-making or communicating decisions, and functional disability. Fifty-three percent of nursing home residents had a combination of either physical or mental impairment and an impairment in either self-care or money management. The discussion focuses on the policy and practice implications of significant rates of incapacity among nursing home residents.     

Do Cognitive Behaviour Therapies Validate Cognitive Models of Mood Disorders? A Review of the Empirical Evidence

The efficacy of Cognitive Behaviour Therapy (CBT) in the treatment of depression is now established. However, explanations for the efficacy of CBT are mixed. The evidence needed to support the explanation advanced by cognitive theory is lacking. This paper critically reviews the available empirical evidence. Forty-four outcome or process studies of therapy with depression are reviewed and 21 of these are subjected to a meta-analysis to investigate the relationship between change in cognitions and change in level of depression during different kinds of therapy. Our analysis shows that: (1) change in cognitive style occurs in all four categories of treatment: CBT, Drug Therapy, Other-Psychological Therapy, and Waiting List; (2) there was a significant difference between Waiting List and all the active treatments in change in cognitions, but not between active treatments; (3) the degree of change in cognitive style is significantly related to change in depression as measured by the Beck Depression Inventory (BDI), but not the Hamilton Rating Scale for Depression (HRS-D); and (4) the relationship between cognitive change and depression is not unique to CBT. Our findings show that CBT does provide some support for the cognitive models of depression but the relationship between cognitive change and recovery from depression is not unique to CBT.     

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.