Target eccentricity effects for defensive responses

Defensive actions involving goal-directed responses to visual stimuli presented in different parts of the viewing field commonly include movements either toward (TOWARD) or away from (AWAY) the actual stimulus. One can categorize the type of defensive movements by outcome or the level of stimulus-response (S-R) compatibility, where a congruent response corresponds to a response in the TOWARD condition and an incongruent response corresponds to a response in the AWAY condition. In an effort to better understand defensive responses, which have received less attention in the literature than offensive movements regardless of their importance in combative situations, we studied the responses of quick yaw head rotations in the TOWARD and AWAY conditions to visual stimuli presented in different parts of the viewing field. In the first experiment (chapter 2) we examined the test-retest reliability of the primary and secondary measures associated with the quick yaw head rotations. After achieving an acceptable level of reliability for most measures, we investigated the effects of S-R compatibility and target eccentricity on the primary measures of reaction time of head rotation (RT) and activity of the sternocleidomastoid muscles of the neck (premotor RT) and the secondary measures of movement time, peak velocity, head excursion and the electromechanical delay for yaw head rotations (chapter 3). We found an increase in RT and premotor RT for yaw head rotations with large increases in visual field target eccentricity and involving incongruent responses observed in the AWAY condition. In chapter 4 we examined the effects of practice in the TOWARD or AWAY condition on performances in both conditions. We observed a shorter RT and premotor RT after 6 days of practice (over 2 weeks), regardless of condition practiced or of performance. Most subjects who practiced in the TOWARD condition produced greater decreases in RT and premotor RT for the TOWARD condition and most subjects who practiced in the AWAY condition produced greater decreases in RT and premotor RT for the AWAY condition. These data also suggest faster reactions in response to stimuli in the central visual field occur with practice. These results suggest reactions will be slowest for responses to objects in the far peripheral visual field and when trying to avoid object contact. RT and premotor RT at each eccentricity and for each condition can definitely improve with practice. The present results also provide small but potential added benefits for specificity of condition training. The parallel findings for RT and premotor RT suggest that outcomes observed for quick yaw head rotation RTs were primarily due to changes in neural processing time

The impact of predictability on dual-task performance and implications for resource-sharing accounts.

The aim of this study was to examine the impact of predictability on dual-task performance by systematically manipulating predictability in either one of two tasks, as well as between tasks. According to capacity-sharing accounts of multitasking, assuming a general pool of resources two tasks can draw upon, predictability should reduce the need for resources and allow more resources to be used by the other task. However, it is currently not well understood what drives resource-allocation policy in dual tasks and which resource allocation policies participants pursue. We used a continuous tracking task together with an audiomotor task and manipulated advance visual information about the tracking path in the first experiment and a sound sequence in the second experiments (2a/b). Results show that performance predominantly improved in the predictable task but not in the unpredictable task, suggesting that participants did not invest more resources into the unpredictable task. One possible explanation was that the re-investment of resources into another task requires some relationship between the tasks. Therefore, in the third experiment, we covaried the two tasks by having sounds 250 ms before turning points in the tracking curve. This enabled participants to improve performance in both tasks, suggesting that resources were shared better between tasks

Predictability improves dual-task performance: the effects of explicit and implicit learning

Predictability is increasingly recognized as an important principle in perception and motor learning. The pursuit of increased predictability seems to one of the main goals that the human system pursues. Therefore, providing predictability in one of the most challenging situations that humans face, namely multitasking, a promising line of research. In this thesis the impact of predictability was systematically investigated in five experiments. In the first four experiments predictability was achieved by implementing a repeating pattern in one task, or both tasks. Participants acquired knowledge of these patterns either explicitly or implicitly in several training sessions, under single-task or dual-task conditions. We tested whether this increased predictability helped dual-task performance after the training sessions. The results suggest that predictability is helpful for dual-task performance, although the benefits are confined to the predictable task itself. In a fifth experiment we focused on providing between task predictability, which led to a large performance improvement in both tasks, prompting the discussion about what constitutes a task, in the sense of when can two tasks be perceived as a single task comprising both, a theoretical problem we tried to tackle in one of the articles. Explanations for the findings, theoretical implications, methodological issues and suggestions for future research are given in the general discussio

Nineteenth Annual Conference on Manual Control

No abstract availabl

Human operator performance of remotely controlled tasks: Teleoperator research conducted at NASA's George C. Marshal Space Flight Center

The capabilities within the teleoperator laboratories to perform remote and teleoperated investigations for a wide variety of applications are described. Three major teleoperator issues are addressed: the human operator, the remote control and effecting subsystems, and the human/machine system performance results for specific teleoperated tasks

Hemispheric Effects of Response Hand and Concurrent Auditory and Visual Information Processing on Task Performance

Previous research (cf. Wickens, Mountford & Schreiner, 1981; Wickens & Sandry, 1982) has suggested that performance is facilitated by maintaining integrity between the hemisphere of information input, processing, and motor response. This task-hemispheric integrity has been found to exist during concurrent performance of verbal and spatial tasks, both of which are presented in a visual modality. The present study sought to examine whether task-hemispheric integrity exists during concurrent performance of a verbal and a spatial task when the verbal task is presented in an auditory modality and the spatial task(s) are presented in a visual modality. Fifty-six individuals (28M, 28F) performed an auditory dichotic listening task alone and concurrently with three spatial tasks, each loading on a different stage of information processing. The results indicate a differential effect of each of the spatial tasks on dichotic listening performance, with few reciprocal effects of the dichotic listening task on spatial task performance. Sex differences were also found on two of the spatial tasks. Potential theoretical and practical implications of the findings are discussed