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Biomedical subjects

P A Hancock

Publications and source records attributed to P A Hancock.

At least 19 recordsLinked to original sources
PubMed2006

The influence of perceptual speed regulation on speed perception, choice, and control: tunnel wall characteristics and influences.

The present work sought to determine if the type of visual pattern and presence of texture applied to transportation tunnel walls differentially affected driving performance. Choice of speed and speed control were measured with 32 participants who drove through a simulated transportation tunnel environment. Participants experienced three visual patterns consisting of vertical segments that decreased, increased, and remained a constant width throughout the length of the tunnel. Participants also drove a baseline control condition in which no visual pattern was present. Each of these conditions was presented either with or without a homogenous texture. When compared to the baseline condition, results indicated drivers gradually decreased speed when exposed to the decreasing width visual pattern and increased speed with the increasing width visual pattern. The presence of texture served to attenuate overall driving speed. Results suggest drivers' perception of speed and their subsequent response to such perceptions were modified by the visual pattern and texture expressed on the tunnel wall. The evident speed control opportunities afforded to the traffic engineer are discussed.

Acceleration↗
PubMed2003

Behavioural accident avoidance science: understanding response in collision incipient conditions.

Road traffic accidents are the single greatest cause of fatality in the workplace and the primary cause of all accidental death in the US to the age of 78. However, behavioural analysis of response in the final seconds and milliseconds before collision has been a most difficult proposition since the quantitative recording of such events has largely been beyond cost feasibility for road transportation. Here, a new and innovative research strategy is reported that permits just such a form of investigation to be conducted in a safe and effective manner. Specifically, a linked simulation environment has been constructed in which drivers are physically located in two adjacent, full-vehicle simulators acting within a shared single virtual driving world. As reported here for the first time, this innovative technology creates situations that provide avoidance responses paralleling those observed in real-world conditions. Within this shared virtual world 46 participants (25 female, 21 male) were tested who met in two ambiguous traffic situations: an intersection and a hill scenario. At the intersection the two drivers approached each other at an angle of 135 degrees and buildings placed at the intersection blocked the view of both drivers from early detection of the opposing vehicle. The second condition represented a 'wrong' way conflict. Each driver proceeded along a three-lane highway from opposite directions. A hill impeded the oncoming view of each driver who only saw the conflicting vehicle briefly as it crested the brow of the hill. Driver avoidance responses of steering wheel, brake, and accelerator activation were recorded to the nearest millisecond. Qualitative results were obtained through a post-experience questionnaire in which participants were asked about their driving habits, simulator experience and their particular response to the experimental events which they had encountered. The results indicated that: (1) situations have been created which provided avoidance responses as they have been recorded in real-world circumstances, (2) the recorded avoidance responses depended directly upon viewing times, and (3) the very short viewing times in this experiment resulted in a single avoidance action, largely represented by a random choice of swerve to either right or left. The present results lead us to posit that in order to be able to design accident avoidance mechanism that respond appropriately in the diverse situations encountered, there is a need to pay particular attention to mutual viewing times for drivers. The general implications for a behavioural science of collision-avoidance are evaluated in light of the present findings.

Accidents, Traffic↗
PubMed2003

The distraction effects of phone use during a crucial driving maneuver.

Forty-two licensed drivers were tested in an experiment that required them to respond to an in-vehicle phone at the same time that they were faced with making a crucial stopping decision. Using test track facilities, we also examined the influence of driver gender and driver age on these dual-task response capacities. Each driver was given task practice and then performed a first block of 24 trials, where one trial represented one circuit of the test track. Half of the trials were control conditions in which neither the stop-light was activated nor was the in-vehicle phone triggered. Four trials required only stop-light response and a further four, phone response only. The remaining four trials required the driver to complete each task simultaneously. The order of presentation of specific trials was randomized and the whole sequence was repeated in a second block giving 48 trials per driver. In-vehicle phone response also contained an embedded memory task that was evaluated at the end of each trial circuit. Results confirmed our previous observation that in the dual-task condition there was a slower response to the light change. To compensate for this slowed response, drivers subsequently brake more intensely. Most importantly, we recorded a critical 15% increase in non-response to the stop-light in the presence of the phone distraction task which equates with increased stop-light violations on the open road. These response patterns varied by driver age and driver gender. In particular, age had a large effect on task components that required speed of response to multiple, simultaneous demands. Since driving represents a highly complex and interactive environment, it is not possible to specify a simplistic relationship between these distraction effects and outcome crash patterns. However, we can conclude that such in-vehicle technologies erode performance safety margin and distract drivers from their critical primary task of vehicle control. As such it can be anticipated that a causal relation exists to collision events. This is a crucial concern for all in-vehicle device designers and for the many safety researchers and professionals seeking to reduce the adverse impacts of vehicle collisions.

Adult↗
PubMed2001

Individual differences in tracking.

The present experiment compared differences in response strategy of participants performing a two-dimensional tracking task at three different levels of task difficulty. Twelve participants tracked an iconic aeroplane target as accurately as possible for nine repeated trials each of 5 min duration. The random input and individual response output were calculated in terms of direction and velocity. Specifically, for each 200-ms sample period, a calculated combination of eight trajectories and three velocities provided a 24 combinatorial description of both random input and participant response. Distributions across these combinations represent descriptive results and reflect individual characteristics. The distributions were compared using the technique of correspondence factor analysis. The outcome of this multidimensional method was that first, between-participants discrimination was best served by the up-vertical and low-velocity combination and, second, that the former pattern typified poor performers, while more skilled individuals used all directional options at the highest velocity level. Implications for individualized controls are examined.

Adult↗
PubMed2000

Fuzzy signal detection theory: basic postulates and formulas for analyzing human and machine performance.

Signal detection theory (SDT) assumes a division of objective truths or "states of the world" into the nonoverlapping categories of signal and noise. The definition of a signal in many real settings, however, varies with context and over time. In the terminology of fuzzy logic, a real-world signal has a value that falls in a range between unequivocal presence and unequivocal absence. The definition of a response can also be nonbinary. Accordingly the methods of fuzzy logic can be combined with SDT, yielding fuzzy SDT. We describe the basic postulates of fuzzy SDT and provide formulas for fuzzy analysis of detection performance, based on four steps: (a) selection of mapping functions for signal and response; (b) use of mixed-implication functions to assign degrees of membership in hits, false alarms, misses, and correct rejections; (c) computation of fuzzy hit, false alarm, miss, and correct rejection rates; and (d) computation of fuzzy sensitivity and bias measures. Fuzzy SDT can considerably extend the range and utility of SDT by handling the contextual and temporal variability of most real-world signals. Actual or potential applications of fuzzy SDT include evaluation of the performance of human, machine, and human-machine detectors in real systems.

Fuzzy Logic↗
PubMed2000

Sex differences in duration judgments: a meta-analytic review.

We quantitatively reviewed human sex differences in the magnitude and variability of duration judgments. Data from 4,794 females and 4,688 males yielded 87 effect size estimates of magnitude and 28 of variability. The overall sex difference in duration judgment magnitude was small but statistically significant. It was moderated by whether study participants knew in advance (prospective paradigm) or only later (retrospective paradigm) that they would be required to judge duration. Although prospective judgments showed no overall sex effect, some levels of moderator variables showed a small but statistically significant effect. Retrospective judgments showed a larger subjective-to-objective duration ratio for females than for males, and several variables moderated this effect. Females' judgments also showed more intersubject variability than did males' judgments. Relative to males, females sustain attention to time more in the prospective paradigm and have better episodic memory in the retrospective paradigm.

Adolescent↗
PubMed1998

Human aging and duration judgments: a meta-analytic review.

Differences in duration judgments made by younger and older adults were reviewed. Previous research is unclear about whether such differences exist and, if so, how they may be explained. The meta-analyses revealed substantial age-related differences. Older adults gave larger verbal estimates and made shorter productions of duration than did younger adults. There were no age-related differences in reproduction of duration or in psychophysical slope relating judged and target duration. Older adults' duration estimates were more variable than were those of younger ones. Findings are discussed in terms of pacemaker rate and attentional resources. An explanation regarding divided attention between nontemporal and temporal information processing best explains the findings.

Adolescent↗
PubMed1998

Human occupational and performance limits under stress: the thermal environment as a prototypical example.

The authors wish to challenge the contemporary stress limits for workers exposed to adverse thermal conditions. Further, they wish to challenge the basis upon which all such occupational stress exposures are founded. It is their contention that task performance level should be the primary criterion for exposure. Change in behavioural performance efficiency is the most sensitive reflection of human response to stress. Such responses are superior as indices of incipient damaging effects compared with the traditional measurement of physiological function. Efficient and error-free performance is the principal criterion of contemporary work, especially in high-technology systems. Therefore, continuing exposure after work performance efficiency begins to fail, but before current physiological limits are reached, is inappropriate for both the safety and the productivity of the individual worker, their colleagues, and the systems within which they operate. Behavioural performance assessment should therefore supercede physiological assessment as the primary exposure criterion, although physiological measures still provide important supplementary information. A new description of such performance thresholds for heat stress is presented, together with its substantive theoretical foundation. Performance limits are of growing importance for prescriptions to all forms of occupational exposure and are critical necessities for future statements concerning comprehensive protective safety standards.

Efficiency↗
PubMed1997

Fatigue, workload and adaptive driver systems.

This paper is directed to the further understanding of the problems of fatigue and workload and their role in diminishing driving capability. We present a specific strategy designed to defend against the adverse effects of fatigue and workload extremes through the use of adaptive driver systems. To begin, the work presents a brief critique of Muscio's constraints on developing a test of fatigue. In criticizing these constraints, we point to the commonalities between all energetic reflections of human performance and use advances in stress theory to explain the problems of and resolution to the question of fatigue. We link fatigue and chronic workload and use this coadunation as a basis for the operation of adaptive driver systems which are specifically designed to combat driving impairment. A specific program is then explained in detail and illustrations are given as to how an extension of previous efforts can address the problem of the drowsy and chronically fatigued driver. Future recommendations are articulated.

Accidents, Occupational↗
PubMed1997

Alarm effectiveness in driver-centred collision-warning systems.

The potential use of systems that seek to communicate a warning of impending collision directly to the driver is examined. Technological advances in collision-warning systems include reliable, low-cost radars, sensors with low noise levels, and the development of accurate detection algorithms for particular crash types, e.g. rear-end collisions. However, fundamental practical constraints make perfect sensor detection difficult to achieve. Imperfect detection conflates the false alarm rate and experience with other technologies confirms driver aversion to false warnings. Although sensitive alarm systems with high detection rates and low false alarm rates have been developed, the posterior probability of a collision given an alarm can be quite low because of the low base rate of collision events. As a result, only a small proportion of alarms will represent true collision scenarios. These and other factors can conspire to reduce alarm effectiveness in collision-warning systems. The problem is illustrated analytically and potential solutions are advanced.

Accidents, Traffic↗
PubMed1997

The perception of spatial layout in real and virtual worlds.

As human-machine interfaces grow more immersive and graphically-oriented, virtual environment systems become more prominent as the medium for human-machine communication. Often, virtual environments (VE) are built to provide exact metrical representations of existing or proposed physical spaces. However, it is not known how individuals develop representational models of these spaces in which they are immersed and how those models may be distorted with respect to both the virtual and real-world equivalents. To evaluate the process of model development, the present experiment examined participant's ability to reproduce a complex spatial layout of objects having experienced them previously under different viewing conditions. The layout consisted of nine common objects arranged on a flat plane. These objects could be viewed in a free binocular virtual condition, a free binocular real-world condition, and in a static monocular view of the real world. The first two allowed active exploration of the environment while the latter condition allowed the participant only a passive opportunity to observe from a single viewpoint. Viewing conditions were a between-subject variable with 10 participants randomly assigned to each condition. Performance was assessed using mapping accuracy and triadic comparisons of relative inter-object distances. Mapping results showed a significant effect of viewing condition where, interestingly, the static monocular condition was superior to both the active virtual and real binocular conditions. Results for the triadic comparisons showed a significant interaction for gender by viewing condition in which males were more accurate than females. These results suggest that the situation model resulting from interaction with a virtual environment was indistinguishable from interaction with real objects at least within the constraints of the present procedure.

Adult↗
PubMed1996

Effects of control order, augmented feedback, input device and practice on tracking performance and perceived workload.

Virtual interfaces to advanced human-machine systems will present operators with a variety of perceptual-motor challenges. To inform the virtual interface design processes, the present experiments examined the effects of track order, level of knowledge of performance, type of control device, and the extent of practice on tracking performance and associated mental workload. Tracking was assessed by root mean square error. Subjective workload was measured using both the NASA Task Load Index (TLX) and the Subjective Workload Assessment Technique (SWAT). Results indicated non-linear effects, where tracking error and subjective workload both increased non-proportionally with track order. Trackball use resulted in more accurate performance and was judged to be of lower subjective workload than input using a mouse. Augmented knowledge of performance had little effect on either performance or workload. There was a number of interactions affecting performance that were replicated in perceived workload. Over acquisition trials, second-order tracking exhibited continuous improvement. This capability was retained even after a 30-day rest interval. Decrease a workload followed performance improvement in both initial acquisition and subsequent retention phases. The two subjective workload scales were essentially equivalent in terms of their sensitivity to task manipulations. These results support the direct association between workload and performance and confirms the use of workload in helping to evaluate the influence of diverse task-related demands. The implications for the design of virtual interfaces to real-world systems are examined in the light of these findings.

Adult↗
PubMed1996

A comparison of the perceived and normative needs for dental care in 12-year-old children in the northwest of England.

The perceived treatment needs for dental caries and orthodontics were recorded for a group of twelve-year-old children. The results were compared with the normative needs, as determined by examiners at routine school examinations prior to, and after training and calibration in the use the BASCD caries diagnostic criteria and the IOTN. Both sets of normative needs were also compared to the results obtained by a third examiner, already trained and calibrated in the use of the indices. It was found that the training and calibration exercises resulted in a statistically significant closer relationship between perceived and normative needs for both dental caries and orthodontic treatment needs. It is concluded that training will be of benefit in treatment needs assessment, as it will take account of perceived treatment needs.

Attitude to Health↗
PubMed1995

Pilot performance and preference for short cycles of automation in adaptive function allocation.

The present experiment examined pilot response to the rapid cycling of automation. The experiment was conducted using a multi-task simulation environment consisting of tracking, fuel management, and system monitoring sub-tasks. Monitoring and fuel management sub-tasks were performed manually in all conditions. The tracking sub-task cycled between manual and automated control at fixed intervals of either 15, 30 or 60 sec. These cycle times were completely crossed with three levels of tracking difficulty giving nine within-subject conditions which lasted 5 min each. Performance was measured on each of the sub-tasks, as was pilot fatigue level and subjective workload for the respective conditions. Results indicated that both difficulty and cycle duration significantly affected tracking performance which was degraded with task difficulty and longer cycle times. Fuel management and system monitoring performance were unaffected by tracking difficulty and automation duration. However, a subsequent analysis was conducted using the 15 sec period immediately following each automation episode as a 'window' of performance. A different pattern of results was observed. Tracking performance was similarly affected by difficulty, but was no longer affected by cycle duration. Furthermore, fuel management error indicated a trend toward better performance in low difficulty conditions. Results illustrate micro trade-offs within sub-tasks and macro trade-offs between sub-tasks. Overall, the results support the contention that excessively short cycles of automation prove disruptive to performance in multi-task conditions.

Journal Article↗
PubMed1995

Effects of jet engine noise and performance feedback on perceived workload in a monitoring task.

This study examined the effects of exposure to intermittent jet aircraft noise (70 dBA or 95 dBA maximum intensity) and knowledge of results concerning signal detections (hit-KR) on performance efficiency and perceived workload in a 40-min visual vigilance task. The noise featured a Doppler-like quality in which planes seemed to approach from the monitor's left and recede to the right. Perceptual sensitivity (d') was poorer in the context of noise than in quiet but only in the presence of hit-KR. The lack of noise-related performance differences in the absence of hit-KR most likely reflected a "floor effect" rather than some special relation between noise and feedback. When compared to subjects performing in quiet, those who operated in noise were less able to profit from hit-KR, a result that may reflect the effects of noise on information processing. In addition to its negative effects on signal detectability, noise elevated the perceived workload, as measured by the NASA-TLX. This effect was robust; it was independent of the presence of hit-KR, even though hit-KR generally lowered the overall level of perceived workload. The results provide the initial experimental demonstration that perceived workload is a sensitive measure of the effects of aircraft noise in monitoring tasks.

Adolescent↗