| 1. |
- Dahlman, Joakim, 1974-, et al.
(författare)
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Could sound be used as a strategy for reducing symptoms of perceived motion sickness?
- 2008
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Ingår i: Journal of NeuroEngineering and Rehabilitation. - : Springer Science and Business Media LLC. - 1743-0003. ; 5:35
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Tidskriftsartikel (refereegranskat)abstract
- Background: Working while exposed to motions, physically and psychologically affects a person. Traditionally, motion sickness symptom reduction has implied use of medication, which can lead to detrimental effects on performance. Non-pharmaceutical strategies, in turn, often require cognitive and perceptual attention. Hence, for people working in high demand environments where it is impossible to reallocate focus of attention, other strategies are called upon. The aim of the study was to investigate possible impact of a mitigation strategy on perceived motion sickness and psychophysiological responses, based on an artificial sound horizon compared with a non-positioned sound source.Method: Twenty-three healthy subjects were seated on a motion platform in an artificial sound horizon or in non-positioned sound, in random order with one week interval between the trials. Perceived motion sickness (Mal), maximum duration of exposure (ST), skin conductance, blood volume pulse, temperature, respiration rate, eye movements and heart rate were measured continuously throughout the trials.Results: Mal scores increased over time in both sound conditions, but the artificial sound horizon, applied as a mitigation strategy for perceived motion sickness, showed no significant effect on Mal scores or ST. The number of fixations increased with time in the non-positioned sound condition. Moreover, fixation time was longer in the nonpositioned sound condition compared with sound horizon, indicating that the subjects used more time to fixate and, hence, assumingly made fewer saccades.Conclusion: A subliminally presented artificial sound horizon did not significantly affect perceived motion sickness, psychophysiological variables or the time the subjects endured the motion sickness triggering stimuli. The number of fixations and fixation times increased over time in the non-positioned sound condition.
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| 2. |
- Dahlman, Joakim, 1974-, et al.
(författare)
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Effects of Motion Sickness on Encoding and Retrieval
- 2010
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Tidskriftsartikel (refereegranskat)abstract
- Objective: In this study, possible effects of motion sickness on encoding and retrieval of words were investigated. Background: The impact of motion sickness on human performance has been studied with regards to psychomotor functions and over learned skills, as well as to novel situations requiring encoding and retrieval skills through the use of short term memory. In this study, possible effects of motion sickness on encoding and retrieval of words were investigated. Method: Forty healthy participants, half of them males, performed a continuous recognition task (CRT) during exposure to a motion sickness triggering optokinetic drum. The CRT was employed as a measurement of performance and consisted of encoding and retrieval of words. The task consisted of three consecutive phases 1) encoding of familiar words; 2) encoding and retrieval of words under the influence of motion sickness; 3) retrieval of words after exposure. Results: Data analysis revealed no significant differences in the ability to encode or retrieve words during motion sickness compared with a control condition. In addition, there were no significant correlations between the level of motion sickness and performance of the CRT. Conclusion: The results indicate that encoding and retrieval of words are not affected by moderate levels of motion sickness. Application: This research has implications for operational settings where professionals experience moderate levels of motion sickness.
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| 3. |
- Dahlman, Joakim, 1974-, et al.
(författare)
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Performance and Autonomic Responses during Motion Sickness
- 2009
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Ingår i: Human Factors. - : SAGE Publications. - 0018-7208 .- 1547-8181. ; 51:1, s. 56-66
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Tidskriftsartikel (refereegranskat)abstract
- Objective: The aim of the study was to investigate how motion sickness, triggered by an optokinetic drum, affects short term memory performance and to explore autonomic responses to perceived motion sickness. Background: Previous research has found motion sickness to decrease performance, but it is not known how short term memory in particular is affected. Method: Thirty-eight healthy participants performed a listening span test while seated in a rotating optokinetic drum. Measurements of motion sickness, performance, heart rate, skin conductance, blood volume pulse, and pupil size were performed simultaneously throughout the experiment. Results: A total of 16 participants terminated the trial due to severe nausea, while the other 22 endured the full 25 minutes. Perceived motion sickness increased over time in both groups, but less among those who endured the trial. Short term memory performance decreased towards the end for those who terminated, while it increased for the other group. Results from the measured autonomic responses were ambiguous. Conclusion: The present study concludes that performance, measured as short term memory, declines as perceived motion sickness progresses. Application: This research has potential implications for command and control personnel in risk of developing motion sickness.
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| 4. |
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| 5. |
- Dahlman, Joakim, 1974-
(författare)
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Psychophysiological and Performance Aspects on Motion Sickness
- 2009
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Motion sickness is not an illness, but rather a natural autonomic response to an unfamiliar or specific stimulus. The bodily responses to motion sickness are highly individual and contextually dependent, making them difficult to predict. The initial autonomic responses are similar to the ones demonstrated when under stress. When under the influence of motion sickness, motivation and ability to perform tasks or duties are limited. However, little is known about how specific cognitive functions are affected. Furthermore, standard mitigation strategies involve medications that induce fatigue or strategies that require cognitive capabilities. Both of them may result in reduced capability to perform assigned tasks or duties. Hence, there is a need for alternative mitigation strategies.The aim of the thesis was to study psychophysiological and performance aspects on motion sickness. The long-term goal is to provide strategies for mitigation and prevention of motion sickness by identifying psychophysiological responses as predictors for both wellbeing and performance. This thesis comprises four studies, in which 91 participants were exposed to two different motion sickness stimuli, either an optokinetic drum or a motion platform. Before the tests, a method for extracting fixations from eye-tracking data was developed as a prerequisite for studying fixations as a possible mitigation strategy for reducing motion sickness. During exposure to stimuli that triggers motion sickness, performance was studied by testing short-term memory and encoding and retrieval. In the final study, the effects of an artificial sound horizon were studied with respect to its potential to subconsciously function as a mitigating source.The results of the measurements of the psychophysiological responses were in accordance with previous research, confirming the ambiguity and high individuality of the responses as well as their contextual dependencies. To study fixations, a centroid mode algorithm proved to be the best way to generate fixations from eye-movement data. In the final study, the effects of the sound horizon were compared to the effects of a non-positioned sound. In the latter condition, both fixation time and the number of fixations increased over time, whereas none of them showed a significant time effect in the sound horizon condition. The fixation time slope was significantly larger in the non-positioned sound condition compared to the sound horizon condition. Number of fixations, heart rate, and skin conductance correlated positively with subjective statements that referred to motion sickness. Among participants that were susceptible to motion sickness symptoms, short-term memory performance was negatively affected. However, no effects of motion sickness on encoding and retrieval were found, regardless of susceptibility.Future studies should continue focusing on autonomic responses and psychological issues of motion sickness. Factors such as motivation, expectancies, and previous experiences play a major and yet relatively unknown role within the motion sickness phenomena.
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| 6. |
- Earl, Robyn, et al.
(författare)
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Visual search strategies of pedestrians with and without visual and cognitive impairments in a shared zone : A proof of concept study
- 2016
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Ingår i: Land use policy. - : Elsevier. - 0264-8377 .- 1873-5754. ; 57, s. 327-334
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Tidskriftsartikel (refereegranskat)abstract
- Shared zones have gained increasing popularity in urban land use and design as a means of incorporating the needs of multiple modes of transport, while at the same time promoting social interaction between users. Interactions within shared zones are based on a set of informal social protocols, communicated via eye contact and social cues. This proof of concept study utilised eye-tracking technology to examine the visual search strategies of individuals, with and without visual and cognitive impairments as they navigated a strategically chosen shared zone. In total 3960 fixations were analysed and the fixations were distributed across the shared zone and a pedestrian crossing. Those with impairments were more likely to fixate on traffic specific areas and objects compared to those without, suggesting that they required more input ascertaining when and where it was safe to perform tasks. However, the duration of fixation was not significantly different for an object whether it was traffic related or not, indicating a global need for increased processing time of the surrounding environment. Shared zones are claimed to increase driver awareness and safety and reduce congestion, but the implications on participation and safety for those with visual and cognitive impairments is yet to be extensively explored.
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| 7. |
- Sjörs, Anna, 1981-, et al.
(författare)
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Effects of motion sickness on encoding and retrieval performance and on psychophysiological responses
- 2010
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Tidskriftsartikel (refereegranskat)abstract
- Motion sickness has previously been found to deteriorate performance, e.g., regarding psychomotor functions and short term memory. Sustained ability to perform, despite motion sickness, is crucial in complex working environments. This study focuses on effects of motion sickness on encoding and retrieval of words through the use of long term memory. In addition, the temporal development of different psychophysiological responses and their relationship with perceived motion sickness were investigated. Forty healthy participants performed an encoding and retrieval task during exposure to an optokinetic drum. The results were compared with data from 20 controls that performed the task without motion sickness exposure. Measurements of heart rate, heart rate variability, skin conductance, blood volume pulse, respiration rate, and skin temperature were made throughout optokinetic drum exposure. Data analyses revealed no significant effects of moderate levels of motion sickness on the ability to encode or retrieve words. We found positive relationships between subjective motion sickness ratings and heart rate, blood volume pulse and skin temperature whereas respiration rate was negatively related to perceived motion sickness. The psychophysiological measurements did not show consistent patterns of sympathetic activation and parasympathetic withdrawal, as could be expected. Hence, they are not recommended as predictors of motion sickness.
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| 8. |
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| 9. |
- Dahlman, Joakim, et al.
(författare)
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Perceived motion sickness and effects on performance following naval transportation
- 2012
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Ingår i: Journal of human performance in extreme environments. - : The Society for Human Performance in Extreme Environments. - 1529-5168 .- 2327-2937. ; 10:1
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Tidskriftsartikel (refereegranskat)abstract
- The present study focused on the relationship between previous experiences of, and rated susceptibility to, motion sickness and its correlation to subjective measurements and actual performance. Performance was measured in terms of shooting precision among 23 participants from the Swedish amphibious corps after transportation in a small amphibious boat, while sealed off with no reference to the outside world. Self-rating questionnaires were collected regarding perceived performance and presence of motion sickness. The physiological status perceived by each participant was related to factors that generally indicate early stages of motion sickness, which also were correlated to deficits in performance. It was further shown that participants who believed that their performance could be affected by motion sickness also performed less well.
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| 10. |
- Falkmer, Torbjörn, et al.
(författare)
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Fixation identification in centroid versus start-point modes using eye-tracking data
- 2008
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Ingår i: Perceptual and Motor Skills. - : Sage Publications. - 0031-5125 .- 1558-688X. ; 106:3, s. 710-724
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Tidskriftsartikel (refereegranskat)abstract
- Fixation-identification algorithms, needed for analyses of eye movements, may typically be separated into three categories, viz. (i) velocity-based algorithms, (ii) area-based algorithms, and (iii) dispersion-based algorithms. Dispersion-based algorithms are commonly used but this application introduces some difficulties, one being optimization. Basically, there are two modes to reach this goal of optimization, viz., the start-point mode and the centroid mode. The aim of the present study was to compare and evaluate these two dispersion-based algorithms. Manual inspections were made of 1,400 fixations in each mode. Odds ratios showed that by using the centroid mode for fixation detection, a valid fixation is 2.86 times more likely to be identified than by using the start-point mode. Moreover, the algorithm based on centroid mode dispersion showed a good interpretation speed, accuracy, robustness, and ease of implementation, as well as adequate parameter settings.
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