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Biomedical subjects

T J Triggs

Publications and source records attributed to T J Triggs.

9 recordsLinked to original sources
PubMed2001

Characteristics of cursor trajectories controlled by the computer mouse.

An analysis of computer screen cursor trajectories can provide insights into the factors limiting efficient cursor positioning and can assist in the design of human-computer interfaces. Cursor locations as controlled by a Microsoft computer mouse with standard settings were therefore sampled at 5 ms intervals and kinematic analyses addressed the proportions of time spent in the initiation, accelerative and terminal guidance phases of cursor positioning. Twelve participants used a computer mouse to move a cursor over different distances (7.5 cm, 15 cm) from a home location in the lower centre of the screen to targets of different diameters (8 mm, 16 mm), situated to the left, middle or right of the computer screen. Cursor trajectories were irregular, and participants regularly overshot their targets, spending 70% of movement duration in terminal guidance. Participants appeared to use the initial part of their movement to establish mappings between controller and display. Interventions should seek to reduce the terminal guidance phase of cursor positioning.

Adult↗
PubMed2001

Cursor orientation and computer screen positioning movements.

Implicit directional cues in arrowhead cursors could influence positioning of a cursor on the screen of the computer. Performance during cursor placement may benefit from compatibilities between cursor orientation and direction of movement. Arrowheads could also elicit illusory processes that may affect judgments of (a) the distances on the screen or (b) the location of the point of the arrowhead. To address the impact of the cursor's orientation on its positioning, we had 12 participants move cursors (crosshairs, leftward, or rightward arrow) leftward or rightward to targets (near, far) on a computer screen. Movement amplitude was more important than cursor orientation for initiation of rightward movements, whereas cursor orientation affected the duration of leftward movements and movements to farther targets. Arrowhead orientation contributed to the greater overshooting of far targets. There was little evidence that compatibility of orientation and direction of movement assisted response initiation or execution, and there was little indication that arrowhead cursors led to illusory effects that influenced cursor placement. Arrowhead cursors can provide irrelevant stimulus dimensions that distract users. This work can be applied to the design of cursors in graphical user interfaces. The use of orientation-neutral cursors or cursors whose stimulus dimensions are more relevant is recommended.

Adult↗
PubMed1998

Interactive effects of sleep deprivation, time of day, and driving experience on a driving task.

Performance decrements after more than 24 hours of sleep deprivation (SD) are not only a monotonic function of the duration of SD, but are the result of an interaction between SD and time of day. The major deteriorations in performance during SD are still evident throughout the night, as in the non-sleep-deprived state. Twelve experienced and 12 inexperienced drivers drove a driving simulator for 20 minutes at 0800, 1100, 1400, 1700, and 2000 hours on two testing days. One testing day was conducted after a normal night's sleep, and the other after one night of SD. Reaction time (RT) was also measured while driving. The standard deviation of both lateral position and speed were significantly higher during SD. Performance steadily improved across the day between 0800 and 2000 hours, and the absence of any sleep-by-time interactions suggests that the rhythm of driving performance across the day was similar after both normal sleep and SD. Inexperienced drivers had higher RTs than experienced drivers in both sleep-deprived and non-sleep-deprived conditions. These results have important implications for those involved in the transport industry.

Adult↗
PubMed1997

Time of day variations in driving performance.

Numerous factors may contribute to the 24-hour pattern of automobile accidents. One factor may be a time of day variation in driving ability. In the present study, 11 male subjects operated a driving simulator for 30 minutes at six times of day. Subjects were instructed to maintain a stable position in the left-hand lane and to drive at a constant speed of 80 km/hour. In addition subjects performed a secondary reaction time task. Subjective mood was measured at the beginning and end of each session. Driving performance was measured in terms of the mean and standard deviation of lateral position and speed. The mean and standard deviation of speed varied significantly across the day for both curved and straight segments. Reaction time was also affected by time of day. Performance was more impaired at 0600 and 0200 hours, with improvements in driving performance between 1000 and 2200 hours and an early afternoon dip. These results suggest that driving performance is subject to diurnal variations. Of particular importance is the result that impairments in driving performance in the early afternoon are of a similar magnitude to those occurring in the late evening and early morning.

Accidents, Traffic↗
PubMed1992

Apparent size and distance in an imaging display.

The size-distance invariance hypothesis suggests that the perceived size and the perceived distance of objects in a field viewed naturally are closely related. However, this relationship breaks down when scenes are viewed through high-power optical systems. When natural scenes are viewed through an imaging display of unity magnification, there is a reduction in their apparent size. This raises the question of whether the relationship breaks down when scenes are viewed through a low-power imaging display. A single-lens reflex camera was used as an imaging display that enabled subjects to vary the size of imaged real-world scenes. Judgments of size were found to vary with depth information in scenes and between monocular and binocular viewing, consistent with a previous finding, but judgments of distance did not vary significantly across either of these conditions. The results suggest that judgments of size and judgments of distance with imaging displays are not influenced uniformly by environmental and task variables.

Adult↗
PubMed1989

Visual accommodation and target detection in the vicinity of a window post.

The visual environment of a driver in a car or a pilot in an airplane has intervening objects from the vehicle such as A-pillar posts between the windscreen and the doors in the car or cockpit pillars in the airplane. The presence of such objects can bias the observer's visual accommodation response because of the Mandelbaum effect (e.g., Owens, 1979). When subjects were allowed to focus toward a distance by looking through a large aperture in an intervening post, the detection (monocular) of a briefly presented distant target was found to be significantly better than when no aperture was present. When the size of the aperture was decreased from 2.3 to 1.15 deg diameter, target detection performance was significantly decreased and remained constant as further reduction of foveal cues was made. Although the detection results were generally in agreement with the visual accommodation results, detection accuracy changed significantly only with marked changes in accommodation. In addition to an accommodation bias, interference to target detection was also observed for those targets occurring at a laterally proximal position to the intervening object.

Accommodation, Ocular↗