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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.
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2.
  • Bertilsson, Johan, et al. (författare)
  • Towards systematic and objective evaluation of police officer performance in stressful situations
  • 2020
  • 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.
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3.
  • Dahl, Mats, et al. (författare)
  • Analysis of eyewitness testimony in a police shooting with fatal outcome–Manifestations of spatial and temporal distortions
  • 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.
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4.
  • 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 .- 1068-316X. ; 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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5.
  • Dahl, Mats (författare)
  • Processing Asymmetries of Emotionally Valenced Stimuli
  • 2002
  • Doktorsavhandling (övrigt vetenskapligt)abstract
    • The central phenomenon investigated concerns the valence-based process asymmetry found in several earlier studies (e.g. Pratto & John, 1991; Taylor, 1991), where negative stimuli seem to initiate more thorough processing than positive stimuli. This finding was consistent in the three empirical studies forming this dissertation. In Study 1 (three experiments) emotionally valenced words were presented at the centre of pictures of emotional faces (angry, sad, disgusted, happy). The results showed a general positive valence advantage (PVA) in reaction times for positive words relative to negative words. Furthermore, except for the words imposed on pictures of angry faces in the first experiment, the PVA increased when words were imposed on pictures of happy faces. In Study 2, the priming effects of emotional words were tested. In both experiments, two conditions were used. When valence had been activated by a valence categorisation task, negatively primed words resulted in prolonged RTs in a subsequent word recognition test. In the other condition, where the participants just read the word, no valence dependent latency differences were found. The results provide support for a non-automatic appraisal of the valence when using words as stimuli.In Study 3 (three experiments) neutral words were imposed on emotional pictures (negative, neutral and positive) in the encoding phase. In the following test phase the phenomenological quality of the memory was measured using the Remember-Know paradigm (Tulving, 1985). The results showed a decrease in the frequency of “remember” responses, suggesting less episodic detail in the retention experience of the to-be-remembered item, when the words had been presented on negative pictures relative to positive pictures. The third experiment tested whether the neutral words were primed by the valence of the encoding context (picture) and whether such affective information could be used as a cue in a subsequent source monitoring task (Johnson, Hashtroudi, Lindsay, 1993). However, no support for the valence-as-a-cue hypothesis was found. The results of the three studies are discussed within the framework of appraisal theories (Lazarus, 1991; Scherer, 2001) and Taylor’s mobilization-minimization hypothesis, and an evolutionary explanation for the processing asymmetry is considered.
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6.
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7.
  • Dahl, Mats, et al. (författare)
  • The effect of emotional valance on recollective experience and confidence judgments
  • 2003
  • Ingår i: Psychology & Law International Interdisciplinary Conference 2003,2003-07-07 - 2003-07-12. ; , s. 110-110
  • Konferensbidrag (refereegranskat)abstract
    • The study investigated the effect of positive and negative emotional valence (I.A.P.S pictures) on recollective experience, using the remember-know paradigm (Tulving, 1985), and confidence judgements. The negative valenced pictures were hypothesised elicit the recollective experience to a larger extent and to entail a higher degree of confidence in the correctness of memory responses than positive valenced pictures. In the acquisition phase of all three experiments four pictures were presented simultaneously, one valenced picture (either positive or negative) and three neutral pictures. Next, in the test phase a recognition test of the valenced pictures followed. Depending on the experiment, the participants made new/old responses and either remember/know judgements of old responses or confidence judgements of the correctness of their new/old responses. The results of Experiment 1 and 2 showed that, compared with ”know” responses, the frequency of ”remember” responses was significantly higher for negative than for positive pictures. No differences in recognition memory performance were found between negative and positive pictures. The results of Experiment 3 showed that negative pictures was associated with slightly higher accuracy and significantly higher confidence judgements than positive pictures, and that realism in confidence judgements did not differ between the valence types. These results suggest that the emotional valence of witnessed events affect the phenomenological quality and degree of confidence of memorial testimony.
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8.
  • 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 .- 1939-1498. ; 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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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. Keywords: aging, memory, confidence judgments, realism, general knowledge question
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10.
  • 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 .- 1613-9372. ; 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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