Adaptive tuning of interlimb attraction to facilitate bimanual decoupling

Motor skills that require limbs to concurrently produce different spatiotemporal patterns are often quite difficult to learn. This article outlines a general strategy for training subjects to perform skills that require such disparate limb movements. The strategy is based on the notion that certain preferred movement patterns naturally emerge through the dynamics of the perceptual-motor system, even when quite different movements are intended. The training strategy proposes that the acquisition of relative motion patterns that diverge from preferred patterns can be facilitated by initially "tuning" system dynamics to reduce interlimb attraction. The schedule for the dynamical tuning is adopted from the adaptive training method previously applied to tracking tasks. Preliminary evidence is provided in support of this strategy for learning a bimanual task requiring both structural and metrical interlimb decoupling.     

Prompt comprehension in UNIX command production

We hypothesize that a cognitive analysis based on the construction-integration theory of comprehension (Kintsch, 1988) can predict what is difficult about generating complex composite commands in the UNIX operating system. We provide empirical support for assumptions of the Doane, Kintsch, and Polson (1989, 1990) construction-integration model for generating complex commands in UNIX. We asked users whose UNIX experience varied to produce complex UNIX commands, and then provided help prompts whenever the commands that they produced were erroneous. The help prompts were designed to assist subjects with respect to both the knowledge and the memory processes that our UNIX modeling efforts have suggested are lacking in less expert users. It appears that experts respond to different prompts than do novices. Expert performance is helped by the presentation of abstract information, whereas novice and intermediate performance is modified by presentation of concrete information. Second, while presentation of specific prompts helps less expert subjects, they do not provide sufficient information to obtain correct performance. Our analyses suggest that information about the ordering of commands is required to help the less expert with both knowledge and memory load problems in a manner consistent with skill acquisition theories.     

Recollective experience, normal aging, and frontal dysfunction.

This study examined the nature of verbal recognition memory in young and old subjects. Following presentation of a word list, subjects undertook a yes-no recognition test and indicated whether their decision was based on explicit recollection or assessment of familiarity. Explicit recollection declined with age, and familiarity-based recognition increased. Furthermore, the extent to which older subjects relied on familiarity-based recognition correlated with neuropsychological indices of frontal lobe dysfunction. A further experiment indicated that the change from explicit recollection to familiarity-based responding was unrelated to changes in older subjects' confidence about their memory. The data indicate the central role of frontal dysfunction in understanding age-related memory loss.     

Which opinion should a clinical ethicist give: Personal viewpoint or professional consensus?

When clinical ethicists are called upon to give a recommendation regarding patient care, they may be faced with a dilemma of their own. If their own personal opinion is not widely shared, the ethicist will have three options. These include: (1) giving their own opinion; (2) giving the widely shared opinion; and (3) giving both opinions, leaving the physician to select which opinion to accept. The intentions of this article are to evaluate strengths and weaknesses of these three alternatives and to suggest that ethics consultants recognize and deal with this issue. Two cases are presented to explore the limitations of each option. The author suggests that when the views of ethics consultants differ from the consensus view, the consultant should give the consensus view, their own dissenting view and the arguments in support of each position.     

Determinants ofthe perception of sagittal motion

This study examines the change in the perceived distance of an object in three-dimensional space when the object andlor the observer’s head is moved along the line of sight (sagittal motion) as a function of the perceived absolute (egocentric) distance of the object and the perceived motion of the head. To analyze the processes involved, two situations, labeled A and B, were used in four experiments. In Situation A, the observer was stationary and the perceived motion of the object was measured as the object was moved toward and away from the observer. In Situation B, the same visual information regarding the changing perceived egocentric distance between the observer and object was provided as in Situation A, but part or all of the change in visual egocentric distance was produced by the sagittal motion of the observer’s head. A comparison of the perceived motion of the object in the two situations was used to measure the compensation in the perception of the motion of the object as a result of the headmotion. Compensation was often clearly incomplete, and errors were often made in the perception of the motion of the stimulus object. A theory is proposed, which identifies the relation between the changes in the perceived egocentric distance of the object and the tandem motion of the object resulting from the perceived motion of the head to be the significant factor in the perception of the sagittal motion of the stimulus object in Situation B.     

Mental models and temporal reasoning

We report five experiments investigating reasoning based on temporal relations, such as: “John takes a shower before he drinks coffee”. How individuals make temporal inferences has not been studied hitherto, but we conjectured that they construct mental models of events, and we developed a computer program that reasons in this way.As the program shows, a problem of the form:

1. a before b

2. b before c

3. d while b

4. e while c

What is the relation between d and e?

where a, b, c, etc. refer to everyday events, calls for just one model, whereas a problem in which the second premise is modified to c before b calls for multiple models because a may occur before c, after c, or at the same time as c.

Experiments 1–3 showed that problems requiring one mental model elicited more correct responses than problems requiring multiple models, which in turn elicited more correct answers than multiple model problems with no valid answers. Experiment 4 contrasted the predictions of the model theory with those based on formal rules of inference; its results corroborated the model theory. Experiment 5 confirmed that a premise leading to multiple models took longer to read than the corresponding premise in one-model problems, and that latency to respond correctly was greater for multiple-model problems than for one-model problems. We conclude that the experiments corroborate the mental model theory.     

Use of a virtual reality car-driving stressor in cardiovascular reactivity research

Eighteen subjects (11 males, 7 females) completed a virtual reality car-driving stressor on two occasions several weeks apart. Immediately before and throughout task performance, blood pressure, cardiac output, and total peripheral resistance were assessed. Reactivity scores were calculated for each parameter for each subject as the arithmetic difference between task level and baseline level. The task elicited considerable hemodynamic activation on each occasion of testing, as well as high levels of self-reported task realism, engagement, excitement, and nervousness. Correlation analyses of both absolute and reactivity scores revealed evidence of test-retest reliability. Males were found to exhibit greater absolute levels of and greater increases in systolic blood pressure. The development of tasks suitable for inclusion in a battery of behavioral stressors, responses to which may help identify those at risk for later disease, is of considerable interest in cardiovascular behavioral medicine. The present findings suggest that the virtual reality car-driving task may be useful in this context.     

An inexpensive 1-millisecond experiment control interface for IBM PCs and its user-friendly control language

An inexpensive, professionally manufactured, digital I/O experiment control interface for any PC-compatible computer is described. It plugs into a standard printer port and provides 1-msec accuracy for up to 4 inputs and 22 outputs. It also allows experiment control procedures to be written in an easy-to-learn, easy-to-use Experiment Control language (ECBASIC). In addition to many instructions specifically designed to simplify behavioral research, ECBASIC provides for transparent collection and storage of event logs.     

Creating a hypertext markup language document for an information server

This paper briefly overviews the World-Wide Web. It then provides a short tutorial on the use of the hypertext markup language to publish information on the web. Hypertext markup language is a special page-layout language that was developed to help make creating and retrieving information on the web consistent and efficient. Hyperlinks within hypertext markup language make the language especially powerful because they enable the browser to transparently retrieve images, movies, or audio files from virtually any computer on earth simply by clicking on an item displayed on the monitor.