Influence of terminal action requirements on action-centered distractor effects.

Tipper (1985; Q J Exp Psychol A 37:571-590) has suggested that competing responses programmed to distracting stimuli are inhibited based on their relationship to the action being performed. The present paper reports two experiments designed to examine the influence of the terminal action of a task on the allocation of visual attention. Taken together the results suggest that when engaging targets in an environment, which includes distracting stimuli, competing responses are likely to be programmed in parallel and that the relationship between competing responses can include both spatial position and action characteristics.

Influence of operator orientation on relative organizational mapping and spatial compatibility.

Following up on a study by Worringham and Beringer (1989) that examined the influence of operator orientation on visual-motor performance, Experiment 1 employed a choice reaction time paradigm in which participants had to make rapid, discrete movements with a lever in response to a discrete stimulus. In Experiment 2, participants had to synchronize rhythmic movements with an oscillating visual display. Operator orientation with respect to stimulus display and response array locations was varied to examine the influence of global spatial relations. Display orientation was varied to examine the influence of spatial configuration. Mapping rules were varied to examine the effects of spatial mapping. In Experiment 1, the spatial mapping that yielded faster responses was dependent upon the stimulus display-response array configuration and the global relation. Under a parallel configuration, participants appeared to code the spatial aspects of the stimulus display and response in a manner that was unaffected by the global spatial relation. Under an orthogonal configuration, spatial mapping effects were dependent upon the global relation. In Experiment 2, the global spatial relation did not have an impact on the uniformity of co-ordination under different configuration or mapping conditions. Spatial configuration influenced whether or not differences between spatial mapping rules emerged. Together, the results speak to the relative nature of stimulus-response coding that underlie compatibility phenomena. In addition, the results have potential importance for the design of human-machine systems that allow flexibility in operator orientation.

Monocular and binocular vision in the control of goal-directed movement.

In the present research the authors examined the time course of binocular integration in goal-directed aiming and grasping. With liquid-crystal goggles, the authors manipulated vision independently to the right and left eyes of 10 students during movement preparation and movement execution. Contrary to earlier findings reported in catching experiments (I. Olivier, D. J. Weeks, K. L. Ricker, J. Lyons, & D. Elliott, 1998), neither a temporal nor a spatial binocular advantage was obtained in 1 grasping and 2 aiming studies. That result suggests that, at least in some circumstances, monocular vision is sufficient for the precise control of limb movements. In a final aiming experiment involving 3-dimensional spatial variability and no trial-to-trial visual feedback about performance, binocular vision was associated with greater spatial accuracy. Binocular superiority appeared to be most pronounced when participants were unable to adjust their limb control strategy or procedure on the basis of terminal feedback about performance.

Hand deviations toward distractors. Evidence for response competition.

It has been suggested that, when movements are planned within cluttered environments, competing responses programmed to distracting stimuli are inhibited based on their relation to the action being performed. Further, as a result of this inhibition, the path of the movement made to the target object deviates away from the distractor. In contrast to the object avoidance hypothesis, the results of the present study show that, for aiming movements made in environments in which distractors are present, the path of the movement veers toward the distractor. Moreover, the effects of the distractors on the movement trajectory were independent of the direction of limb movement. These findings suggest that, when a distractor is not a potential physical barrier, a response to the distractor may be activated along with the target response and, owing to temporal advantages, cause a deviation of the movement trajectory toward the distractor.

Monocular and binocular vision in one-hand ball catching: interocular integration.

In 2 experiments, binocular and monocular vision were compared and interocular integration in 1-hand ball catching was examined. Participants (N = 10 in each experiment) were required to catch tennis balls projected over a distance of 15 m. Participants wore liquid-crystal visual occlusion goggles so that the duration and frequency of visual samples provided to their eyes over ball flight could be manipulated. An examination of catching performance indicated that binocular vision contributed to both the spatial and temporal aspects of the catching task. Experienced catchers are able to integrate information from the 2 eyes over intervals as long as 80-100 ms. When provided with only intermittent monocular samples of ball flight, catching performance deteriorated rapidly as the interval between consecutive samples was increased. Results are discussed both in terms of the sources of visual information useful for the interception of objects and the temporal differences for interocular integration between the perception of form and visual-motor control.

Translating between orthogonally oriented stimulus and response arrays in four-choice reaction tasks.

Three experiments examined performance of four-choice reaction tasks using stimulus and response arrays oriented along parallel or orthogonal axes. All used a procedure in which pairs of locations were precued in advance of the target stimulus. Responses were slower for orthogonal than for parallel stimulus-response sets, but the pattern of relative precuing benefits was similar. Complete transfer occurred when the stimulus array was changed from an orthogonal to a parallel orientation with respect to the response array after three sessions of practice. Transfer was also evident when the orientation of the response array was changed from orthogonal to parallel with respect to the stimulus array, as long as the assignment of stimulus locations to fingers was not altered. The results suggest that coding in the four-choice task is by relative location regardless of whether the stimulus and response sets are oriented orthogonally, and that an additional transformation operation to align the frames of reference is performed for orthogonal orientations.

Stimulus-response compatibility for vertically oriented stimuli and horizontally oriented responses: evidence for spatial coding.

It has previously been shown that, when stimuli positioned above or below a central fixation point ("up" and "down" stimuli) are assigned to left and right responses, the stimulus-response mapping up-left/down-right is more compatible than the mapping up-right/down-left for responses executed by the left hand in the left hemispace, but this relation is reversed for responses executed by the right hand in the right hemispace. In Experiment 1, each hand responded at locations in both hemispaces to dissociate the influence of hand identity from response location, and response location was found to be the determinant of relative compatibility. In Experiment 2 responses were made at the sagittal midline, and an inactive response switch was placed to the left or right to induce coding of the active switch as right or left, respectively. This manipulation of relative location had an effect similar to, although of lesser magnitude than, that produced by physically changing location of the response switch in Experiment 1. It is argued that these results are counter to predictions of a movement-preference account and consistent with the view that spatial coding underlies compatibility effects for orthogonally oriented stimulus and response sets.

Cerebral specialization for spatial processing in adults with Down syndrome.

Cerebral specialization for spatial processing in adults with Down syndrome was examined. In the first experiment, both control and right-handed subjects with Down syndrome exhibited no lateral advantage in a dihaptic shape-matching task, whereas left-handed subjects with Down syndrome displayed an expected left-hand advantage. In a visual field dot enumeration task in the second experiment, all groups exhibited left-field superiority. Thus, atypical cerebral organization of function in adults with Down syndrome appears to be confined to speech perception (Elliott & Weeks, 1993).

Anomalous cerebral lateralization and Down syndrome.

Contrary to Bryden, McManus, and Bulman-Fleming's claim, the dichotic listening and handedness literature indicate that persons with Down syndrome exhibit a unique pattern of cerebral specialization. This pattern creates difficulty for any model of laterality that proposes random specialization of function in the absence of a predisposition toward left hemisphere lateralization for language and motor control.

Cross-modal compatibility effects with visual-spatial and auditory-verbal stimulus and response sets.

Within the visual-spatial and auditory-verbal modalities, reaction times to a stimulus have been shown to be faster if salient features of the stimulus and response sets correspond than if they do not. Accounts that attribute such stimulus-response compatibility effects to general translation processes predict that similar effects should occur for cross-modal stimulus and response sets. To test this prediction, three experiments were conducted examining four-choice reactions with (1) visual spatial-location stimuli assigned to speech responses, (2) speech stimuli assigned to keypress responses, and (3) symbolic visual stimuli assigned to speech responses. In all the experiments, responses were faster when correspondence between salient features of the stimulus and response sets was maintained, demonstrating that similar principles of translation operate both within and across modalities.

Cerebral specialization for speech perception and movement organization in adults with Down's syndrome.

Adults with Down's syndrome and a group of undifferentiated mentally handicapped persons were examined using a free recall dichotic listening procedure to determine a laterality index for the perception of speech sounds. Subjects also performed both the visual and verbal portions of a standard apraxia battery. As in previous research, subjects with Down's syndrome tended to display a left ear advantage on the dichotic listening test. As well, they performed better on the apraxia battery when movements were cued visually rather than verbally. This verbal-motor disadvantage increased as the left ear dichotic listening advantage became more pronounced. It is argued that the verbal-motor difficulties experienced by persons with Down's syndrome stem from a dissociation of the functional systems responsible for speech perception and movement organization (Elliott and Weeks, 1990).

Stimulus-response compatability for moving stimuli: perception of affordances or directional coding?

Michaels reported a compatibility effect in which responses were fastest at the destination of a moving stimulus; she interpreted this "destination" compatibility effect in terms of catching actions "afforded" by the stimulus motion. The present study evaluated implications of the catching-affordance account and compared them with those of an account based on spatial coding of relative direction. The destination compatibility effect was obtained when the responses were keypresses rather that catching movements of a joystick and regardless of whether the stimulus expanded, contracted, or only changed location. This effect was a function of relative rather than absolute location of the responses. A similar compatibility effect was obtained when destinations were designated by static arrow stimuli. The results are inconsistent with the catching-affordance account and are best explained by the coding of relative direction.

Salience of stimulus and response features in choice-reaction tasks.

A pattern of differential reaction time (RT) benefits obtained in spatial-precuing tasks has been attributed to translation processes that operate on mental codes formed to represent the stimulus and response sets. According to the salient-features coding principle, the codes are based on the salient stimulus and response features, with RTs being fastest when the two sets of features correspond. Three experiments are reported in which the stimulus and response sets were manipulated using Gestalt grouping principles. In the first two experiments, stimuli and responses were grouped according to spatial proximity, whereas in the last experiment, they were grouped according to similarity. With both types of manipulations, the grouping of the stimulus set systematically affected the pattern of precuing benefits. Thus, in these experiments, the organization of the stimulus set was the primary determinant of the features selected for coding the stimulus and response sets in the translation process.

Continuation electroconvulsive therapy: preliminary guidelines and an illustrative case report.

Despite renewed interest in ECT as a continuation treatment after an episode of depressive illness, few guidelines for its use are available. Meaningful research findings are few, although the potential benefits and risks of modern continuation ECT merit study. We suggest preliminary guidelines and provide an illustrative clinical example.

'Schizoid' personality in childhood and adult life. II: Adult adjustment and the continuity with schizotypal personality disorder.

In a controlled follow-up study into adulthood of 32 children diagnosed 'schizoid', three-quarters fulfilled DSM-III criteria for schizotypal personality disorder and two developed schizophrenia. Overall their psychosocial adjustment was somewhat, but not markedly, worse than that of other attenders at a child psychiatry clinic, although as a group they remained more solitary, lacking in empathy, oversensitive, with odd styles of communicating, and often with circumscribed interests.

Cerebral specialization and the control of oral and limb movements for individuals with Down's syndrome.

In this paper we review existing research on cerebral specialization in Down's syndrome (DS) individuals, and we present a preliminary model. The model proposes that the cerebral organization of DS persons is such that there is a dissociation of brain areas responsible for speech perception and the production of complex movement including speech. Research is presented that confirms some initial predictions of the model.

Manual and oral praxis in adults with Down's syndrome.

Mentally handicapped adults with and without Down's syndrome performed single movements and movement sequences following both verbal and demonstration cueing conditions. While the type of cue did not influence the performance of control subjects, Down's syndrome individuals exhibited more error following verbal cueing. These findings could not be explained on the basis of verbal encoding differences between the groups. The results support the notion that Down's syndrome persons suffer from a dissociation of the functional system responsible for speech perception and the system involved with the organization of complex movement.