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Sökning: FÖRF:(Mats Dahl)

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1.
  • Bertilsson, Johan, et al. (författare)
  • Stress Levels Escalate When Repeatedly Performing Tasks Involving Threats
  • 2019
  • Ingår i: Frontiers in Psychology. - Frontiers. - 1664-1078. ; 10, s. 1562-1562
  • Tidskriftsartikel (refereegranskat)abstract
    • Police work may include performing repeated tasks under the influence of psychological stress, which can affect perceptual, cognitive and motor performance. However, it is largely unknown how repeatedly performing stressful tasks physically affect police officers in terms of heart rate and pupil diameter properties. Psychological stress is commonly assessed by monitoring the changes in these biomarkers. Heart rate and pupil diameter was measured in 12 male police officers when performing a sequence of four stressful tasks, each lasting between 20 and 130 s. The participants were first placed in a dimly illuminated anteroom before allowed to enter a brightly lit room where a scenario was played out. After each task was performed, the participants returned to the anteroom for about 30 s before performing the next sequential task. Performing a repeated sequence of stressful tasks caused a significant increase in heart rate (p = 0.005). The heart rate started to increase already before entering the scenario room and was significantly larger just after starting the task than just before starting the task (p < 0.001). This pattern was more marked during the first tasks (p < 0.001). Issuance of a verbal "abort" command which terminated the tasks led to a significant increase of heart rate (p = 0.002), especially when performing the first tasks (p = 0.002). The pupil diameter changed significantly during the repeated tasks during all phases but in a complex pattern where the pupil diameter reached a minimum during task 2 followed by an increase during tasks 3 and 4 (p ≤ 0.020). During the initial tasks, the pupil size (p = 0.014) increased significantly. The results suggest that being repeatedly exposed to stressful tasks can produce in itself an escalation of psychological stress, this even prior to being exposed to the task. However, the characteristics of both the heart rate and pupil diameter were complex, thus, the findings highlight the importance of studying the effects and dynamics of different stress-generating factors. Monitoring heart rate was found useful to screen for stress responses, and thus, to be a vehicle for indication if and when rotation of deployed personnel is necessary to avoid sustained high stress exposures.
2.
  • Bertilsson, Johan, et al. (författare)
  • Towards systematic and objective evaluation of police officer performance in stressful situations
  • 2019
  • Ingår i: Police Practice and Research. - Taylor & Francis. - 1561-4263.
  • Tidskriftsartikel (refereegranskat)abstract
    • To ensure a continuous high standard of police units, it is critical to recruit people who perform well in stressful situations. Today, this selection process includes performing a large series of tests, which still may not objectively reveal a person’s capacity to handle a life-threatening situation when subjected to high levels of stress. To obtain more systematic and objective data, 12 police officers were exposed to six scenarios with varying levels of threat while their heart rate and pupil size were monitored. The scenarios were filmed and six expert evaluators assessed the performance of the police officers according to seven predefined criteria. Four of the scenarios included addressing a moderate threat level task and the scenarios were executed in a rapid sequence. Two further scenarios included a familiar firearm drill performed during high and low threat situations. The results showed that there was a large agreement between the experts in how they judged the performance of the police officers (p < 0.001). Performance increased significantly over tasks in four of the seven evaluation criteria (p ≤ 0.037). There was also a significant effect of pupil size (p = 0.004), but not heart rate, when comparing the different sequential scenarios. Moreover, a high level of threat considerably impaired the motor performance of the police officers during the firearms drill (p = 0.002). Finally, the pupil seemed to systematically dilate more when a threat appeared immediately than with a delay in the scenarios (p = 0.007). We conclude that systematic and quantitative judgments from experts provide valuable and reliable information about the performance of participants in realistic and stressful policing scenarios. Furthermore, objective physiological measures of heart rate and pupil size may help to explain and understand why performance sometimes deteriorates.
3.
  • Dahl, Mats, et al. (författare)
  • Analysis of eyewitness testimony in a police shooting with fatal outcome–Manifestations of spatial and temporal distortions
  • 2018
  • Ingår i: Cogent Psychology. - Cogent OA. - 2331-1908. ; 5:1, s. 1-10
  • Tidskriftsartikel (refereegranskat)abstract
    • Eyewitness statements are commonly used in the criminal justice system and viewed as having a high-probative value, especially when the witness has no motive to lie, other witness recollection corroborates the account, or the witness is highly confident. A fatal police shooting incident in Sweden had 13 witnesses (nine civilians and four police officers) and was also filmed with two mobile phones. All interviews were conducted before witnesses viewed the films, allowing for the analysis of discrepancies between their statements and the videos. In this incident, a police patrol was sent to find out a man who was reported to have attacked two persons with a knife. When found, the perpetrator refused to obey the officer’s commands, and the police eventually shot at him. The analysis showed clear differences between the witness testimonies and the film. Elements associated with perceived threat, for example, the assailant’s armament and movement direction and number of shots fired, were remembered fairly accurately. However, most witnesses poorly recollected when, that is, after which shot, the assailant fell to the ground. Moreover, memory of the actual order of events was altered and important aspects omitted that were crucial from a legal point of view.
4.
  • Lundgren-Kownacki, Karin, et al. (författare)
  • Exploring how a traditional diluted yoghurt drink may mitigate heat strain during medium-intensity intermittent work : : A multidisciplinary study of occupational heat strain
  • 2018
  • Ingår i: Industrial Health. - National Institute of Occupational Safety and Health, Japan. - 0019-8366. ; 56:2, s. 106-121
  • Tidskriftsartikel (refereegranskat)abstract
    • It is common practice in India to consume the dairy drink buttermilk as a way of mitigating occupational heat strain. This paper explores the thermoregulatory and hydration benefits of drinking buttermilk but also the impacts of work in a hot environment on the gut microbiota, renal and cognitive function. Twelve healthy participants were subjected to a 3-h period of medium load physical intermittent work in a climatic chamber (34°C, 60% RH). The subjects were given water, buttermilk (700 ml) or no rehydration at random. Mean body temperatures when no rehydration was given were significantly higher (p ≤ 0.001). When subjects drank water or buttermilk they had a lower sweat rate than with no rehydration (p≤ 0.05) and the perception of feeling hot, uncomfortable, thirsty and physically exerted was significantly reduced (p ≤ 0.05). A hormonal stress response at the end of the exposure was seen when not drinking (p≤ 0.05). No differences in cognitive abilities and gut microbiota were found. The exposure lowered the renal blood flow suggesting an acute impact of short term heat exposure. It was also found that buttermilk has a protective effect on this impact. Our results demonstrated that keeping hydrated by water/buttermilk consumption mitigates heat strain in well-nourished subjects.
5.
  • Sikström, Sverker, et al. (författare)
  • The Role of Sparsely Distributed Representations in Familiarity Recognition of Verbal and Olfactory Materials
  • 2018
  • Ingår i: Cognitive Processing. - Springer. - 1612-4782. ; 19:4, s. 481-494
  • Tidskriftsartikel (refereegranskat)abstract
    • We present the generalized signal detection theory (GSDT), where familiarity is described by a sparse binomial distribution of binary node activity rather than by normal distribution of familiarity. Items are presented in a distributed representation, where each node receives either noise only, or signal and noise. An old response (i.e., a ‘yes’ response) is made if at least one node receives signal plus noise that is larger than the activation threshold, and item variability is determined by the distribution of activated nodes as the threshold is varied. A distinct representation leads to better performance and a lower ratio of new to old item variability, than a more distributed and less distinct representations. Here we apply the GSDT to empirical data on verbal and olfactory memory and suggest that verbal memory relies on a distinct neural item representation whereas olfactory memory has a fuzzy neural representation leading to poorer memory and inducing a larger ratio of new to old item variability.
6.
  • Dahl, Mats, et al. (författare)
  • Old and very old adults as witnesses: event memory and metamemory
  • 2015
  • Ingår i: Psychology, Crime and Law. - Taylor & Francis. - 1477-2744. ; 21:8, s. 764-775
  • Tidskriftsartikel (refereegranskat)abstract
    • Older people constitute an important category of eyewitnesses. Episodic memory performance in older persons is poorer than in younger adults, but little research has been made on older persons' metacognitive judgments. Since more persons of advanced age will likely be called upon as witnesses in coming years, it is critical to characterize this population's metacognitive abilities. We compared event memory metacognition in old adults (66-year-old, n = 74) to very old adults (87 or 90 years old, n = 55). Participants were tested on their memory of a film, using questions with two answer alternatives and the confidence in their answer. As expected, the very old group had a lower accuracy rate than the old group (d = 0.59). The very old group, however, monitored this impairment, since their over-/underconfidence and calibration did not differ from the old group but they displayed a poorer ability to separate correct from incorrect answers (discrimination ability). Possibly, the very old group was able to monitor the level of their over-/underconfidence because they applied general self-knowledge about their memory skills. In contrast, the discrimination of correct from incorrect answers may be more dependent on ability to attend to the features of each retrieved memory.
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7.
8.
  • Dahl, Mats, et al. (författare)
  • The relation between personality and the realism in confidence judgements in older adults
  • 2010
  • Ingår i: European Journal of Ageing. - Springer. - 1613-9380. ; 7:4, s. 283-291
  • Tidskriftsartikel (refereegranskat)abstract
    • This study investigated the relation between personality factors, as measured by the Swedish version of the NEO-FFI questionnaire, and the realism in older adults' (aged 60-93 years, n = 1,384) probability confidence judgements of their answers to general knowledge questions. The results showed very small effect sizes for the contribution of the personality variables to the fit between the proportion correct answers and the level of one's confidence judgements. Although personality differed somewhat within the age span studied and between the genders no differences were found in the relation between the dimensions of the NEO-FFI and the degree of realism in the confidence judgements as a function of age or gender. In total, the results show a significant but very small effect of personality on the realism in older adults' confidence judgements of their semantic knowledge.
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9.
  • Dahl, Mats, et al. (författare)
  • The Realism in Older People's Confidence Judgments of Answers to General Knowledge Questions
  • 2009
  • Ingår i: Psychology and Aging. - American Psychological Association (APA). - 0882-7974. ; 24:1, s. 234-238
  • Tidskriftsartikel (refereegranskat)abstract
    • The study investigated 2 aspects of the accuracy (i.e., realism) of confidence judgments of persons age 60-93 years (N = 1,384) regarding their answers to general knowledge questions. These aspects are the level of confidence (calibration) in relation to the proportion of correct answers and the ability to discriminate between correct and incorrect answers by means of confidence judgments. No age differences were found for either of the 2 aspects. Gender differences were found for proportion of correct answers and confidence but not for the realism in the confidence judgments.
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10.
  • Dahl, Mats, et al. (författare)
  • The relation between realism in confidence judgements and the phenomenological quality of recognition memory when using emotionally valenced pictures
  • 2006
  • Ingår i: Applied Cognitive Psychology. - John Wiley & Sons. - 0888-4080. ; 20:6, s. 791-806
  • Tidskriftsartikel (refereegranskat)abstract
    • The aim of the study was to investigate the relation between the phenomenological quality of memory (Tulving, 1985) and the realism (validity) in confidence judgement when using emotional pictures (I.A.P.S; Lang, Ohman, & Vaitl, 1988). A series of three experiments was completed where the participants judged the phenomenological quality of their memory and/or their confidence. The results showed facilitation for the negative pictures in a matrix search task in the encoding phase, where negative pictures were more easily and quickly detected, compared to positive ones. In the memory phase of the experiments a higher degree of recollective experience (a larger proportion of 'remember' responses) was found for negative pictures. A higher level of confidence for recognition of negative pictures than for positive ones was obtained, but no general valence dependent effect on the realism in the confidence judgement was found. However, when analysing only the remember responses, negative pictures showed higher overconfidence than the positive pictures. The results support that a recollective experience induces higher confidence and overconfidence. Copyright (c) 2006 John Wiley & Sons, Ltd.
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