The effects of irrelevant speech on physiological stress, cognitive performance, and subjective experience - Focus on heart rate variability.

Irrelevant speech impairs cognitive performance, especially in tasks requiring verbal short-term memory. Working on these tasks during irrelevant speech can also cause a physiological stress reaction. The aim of this study was to examine heart rate variability (HRV) as a non-invasive and easy-to-use stress measure in an irrelevant speech paradigm. Thirty participants performed cognitive tasks (n-back and serial recall) during two sound conditions: irrelevant speech (50 dB) and quiet (33 dB steady-state noise). The influence of conditions as well as presentation orders of conditions were examined on performance, subjective experience, and physiological stress. Working during irrelevant speech compared to working during quiet reduced performance, namely accuracy, in the serial recall task. It was more annoying, heightened the perceived workload, and lowered acoustic satisfaction. It was related to higher physiological stress by causing faster heart rate and changes in HRV frequency-domain analysis (LF, HF and LF/HF). The order of conditions showed some additional effects. When speech was the first condition, 3-back performance was less accurate, and serial recall response times were longer, heart rate was faster, and successive heart beats had less variability (lower RMSSD) during speech than during quiet. When quiet was the first condition, heart rate was faster and reaction times in 3-back were slower during quiet than during speech. The negative effect of irrelevant speech was clear in experience, performance, and physiological stress. The study shows that HRV can be used as a physiological stress measure in irrelevant speech studies.

Sleepy drivers on a slippery road: A pilot study using a driving simulator.

Sleepy drivers have problems with keeping the vehicle within the lines, and might often need to apply a sudden or hard corrective steering wheel movement. Such movements, if they occur while driving on a slippery road, might increase the risk of ending off road due to the unforgiving nature of slippery roads. We tested this hypothesis. Twelve young men participated in a driving simulator experiment with two counterbalanced conditions; dry versus slippery road × day (alert) versus night (sleepy) driving. The participants drove 52.5 km on a monotonous two-lane highway and rated their sleepiness seven times using the Karolinska Sleepiness Scale. Blink durations were extracted from an electrooculogram. The standard deviation of lateral position and the smoothness of steering events were measures of driving performance. Each outcome variable was analysed with mixed-effect models with road condition, time-of-day and time-on-task as predictors. The Karolinska Sleepiness Scale increased with time-on-task (p < 0.001) and was higher during night drives (p < 0.001), with a three-way interaction suggesting a small increased sleepiness with driving time at night with slippery road conditions (p = 0.012). Blink durations increased with time-on-task (p < 0.01) with an interaction between time-of-day and road condition (p = 0.040) such that physiological sleepiness was lower for sleep-deprived participants in demanding road conditions. The standard deviation of lateral position increased with time-on-task (p = 0.026); however, during night driving it was lower on a slippery road (p = 0.025). The results indicate that driving in demanding road condition (i.e. slippery road) might further exhaust already sleepy drivers, although this is not clearly reflected in driving performance.

Speech is special: The stress effects of speech, noise, and silence during tasks requiring concentration.

Effects of noise on people depend on sound level but also on other sound properties. A systematic comparison of the stress effects of speech and noise with the same frequency content is missing. This study compared stress reactions under sound conditions speech (sound level 65 dB LAeq ), noise (65 dB), and silence (35 dB), all having similar relative frequency contents. Fifty-nine participants were exposed to one out of three sound conditions on average for 48 minutes while performing tasks requiring concentration. Acute physiological stress was estimated by measuring stress hormone concentrations in plasma (cortisol and noradrenaline), heart rate variability (HRV), and blood pressure. Psychological stress measures were subjective noise annoyance, workload, and fatigue. Compared to silence and noise, working during speech was more annoying, loading, but less tiring, and led to elevated HRV LF/HF ratio with time. Speech also raised cortisol levels compared with silence. Although noise was more annoying, and raised cortisol levels compared with silence, working during speech was more loading and caused more physiological stress than other sound conditions. Special care should be paid to noise control in workplaces requiring concentration because already exposure to moderate sound level sounds caused clear physiological effects on people.

Suicide by crashing into a heavy vehicle: a focus group study of professional drivers.

Professional heavy vehicle drivers can experience a traumatic event at work when suicidal drivers deliberately crash into their vehicles or a pedestrian jumps in front of them. This study adopts a qualitative approach, aiming to gain an understanding about the psychological and other consequences that these crashes have for this occupational group. We organized a semi-structured focus group meeting with six drivers who reported experiencing a deliberate crash into their vehicle. The meeting was moderated by two psychologists. The participants reported that avoiding the crash was difficult. These events can have long-lasting effects on drivers' well-being although individual differences in the response to the event and coping strategies do exist. Participation in our meeting was regarded as a positive experience. This encourages us to believe that organizing similar meetings that allow drivers under the supervision of professionals to share their own experiences with those who experienced similar events, could perhaps be one way of providing support to such drivers who experienced a traumatic event at work.

Suicide by crashing into a heavy vehicle: Professional drivers' views.

Objective: Every profession has its own safety and health risks. In addition to the risk of being involved in a "normal" road crash, professional heavy vehicle drivers are at risk of becoming victims of people attempting suicide by crashing into their vehicles. Road suicides are not that rare, at least not in Finland, where they represent about 12% of all fatal road crashes. The purpose of this study was to survey professional heavy vehicle drivers about their experiences, views and opinions regarding road suicides.Methods: The sample included heavy vehicle drivers (N = 863) randomly recruited from a transport workers' union.Results: About 18% of the respondents reported a suspected suicide attempt of a motor vehicle driver crashing into their vehicle, with 15% of these (i.e.2.8% of the whole sample) also reporting a resulting crash. More than half of the respondents reported personally knowing another professional driver who had experienced a crash caused by a suicidal driver. Almost 80% of the drivers reported being afraid that someone would attempt suicide by crashing into their vehicle; however, thinking about such a possibility produces a level of anxiety in less than half of all respondents. Most respondents agreed about the challenges of avoiding a crash if somebody deliberately drives their car towards their vehicle.Conclusion: Heavy vehicle drivers perceive road suicides as an occupational risk in their profession. We discuss possible preventive measures against suicide attempts by crashing into a heavy vehicle.

Suicide by crashing into a heavy vehicle: Focus on professional drivers using in-depth crash data.

Objective: Road traffic suicides typically involve a passenger car driver crashing his or her vehicle into a heavy vehicle, because death is almost certain due to the large mass difference between these vehicles. For the same reason, heavy-vehicle drivers typically suffer minor injuries, if any, and have thus received little attention in the research literature. In this study, we focused on heavy-vehicle drivers who were involved as the second party in road suicides in Finland. Methods: We analyzed 138 road suicides (2011-2016) involving a passenger car crashing into a heavy vehicle. We used in-depth road crash investigation data from the Finnish Crash Data Institute. Results: The results showed that all but 2 crashes were head-on collisions. Almost 30% of truck drivers were injured, but only a few suffered serious injuries. More than a quarter reported sick leave following their crash. Injury insurance compensation to heavy-vehicle drivers was just above €9,000 on average. Material damage to heavy vehicles was significant, with average insurance compensation paid being €70,500. Three out of 4 truck drivers reported that drivers committing suicide acted abruptly and left them little opportunity for preventive action. Conclusions: Suicides by crashing into heavy vehicles can have an impact on drivers' well-being; however, it is difficult to see how heavy-vehicle drivers could avoid a suicide attempt involving their vehicle.

Annoyance penalty of periodically amplitude-modulated wide-band sound.

Amplitude modulation exists in many environmental noise types. A penalty has been suggested for legal noise assessment to such sounds, but the scientific evidence is limited. The purpose of this research was to determine the annoyance penalty of amplitude modulated (AM) sound as a function of the modulation frequency fm and depth Dm. A psychoacoustic laboratory experiment was conducted with 40 participants to explore how subjective loudness and annoyance of AM sound depends on fm (from 0.25 to 16 Hz), Dm (from 1 to 14 dB), and overall spectrum (two alternatives). The sounds consisted of both AM sounds and reference sounds without amplitude modulation. The AM sounds were played at 35 dB LAeq, which is typical for environmental noise both indoors and in residential yards. The annoyance penalty increased with increasing fm and Dm. The penalties varied from 4 to 12 dB, when Dm ranged from 4 to 14 dB and fm ranged from 1 to 16 Hz. For the lowest fm= 0.25 Hz, and Dm = 1 dB, no penalty could be suggested. The results suggest a potential need for a penalty for low-level AM sounds for certain ranges of fm and Dm, applied for the periods with AM sound.

Women judging: Is a young male drunk driver perceived as more negligent than a young female drunk driver?

OBJECTIVE: It is well established that young men are the riskiest group of all drivers, and men in general more often drive under the influence of alcohol. However, potentially oversimplified representations such as a "young male problem" and "drunk driving as a male problem" can influence action and reinforce existing attitudes by selectively directing attention to stereotypically consistent behavior. The purpose of this study was to test the hypothesis of possible bias toward young male drivers in the context of drunk driving. METHODS: We have created a scenario study investigating whether the sex of an imaginary young drunk driver would be associated with a different perceived negligence (ranging from 0 = not negligent at all to 10 = extremely negligent) among our participants. These participants were a representative sample of Finnish female driver's license holders. The data for the study were gathered as part of a larger survey study on women's drinking and driving culture. RESULTS: Perceptions of how negligent a person was depended on the age of the respondents such that the older the respondent, the higher the perceived negligence. Perceived negligence was similar for male and female drivers in the scenario; however, there was an interaction effect between driver sex and the age of respondents. The youngest (20-29 years) and 2 oldest (50-69 years) groups of our respondents found the young woman to be more negligent, whereas the opposite occurred for the other 2 groups. CONCLUSIONS: The results of our imaginary scenario study of a representative sample of Finnish female driver's license holders do not support a hypothesis that there would be a negative bias toward young male drivers in the context of drunk driving behavior.

Categorization of natural dynamic audiovisual scenes.

This work analyzed the perceptual attributes of natural dynamic audiovisual scenes. We presented thirty participants with 19 natural scenes in a similarity categorization task, followed by a semi-structured interview. The scenes were reproduced with an immersive audiovisual display. Natural scene perception has been studied mainly with unimodal settings, which have identified motion as one of the most salient attributes related to visual scenes, and sound intensity along with pitch trajectories related to auditory scenes. However, controlled laboratory experiments with natural multimodal stimuli are still scarce. Our results show that humans pay attention to similar perceptual attributes in natural scenes, and a two-dimensional perceptual map of the stimulus scenes and perceptual attributes was obtained in this work. The exploratory results show the amount of movement, perceived noisiness, and eventfulness of the scene to be the most important perceptual attributes in naturalistically reproduced real-world urban environments. We found the scene gist properties openness and expansion to remain as important factors in scenes with no salient auditory or visual events. We propose that the study of scene perception should move forward to understand better the processes behind multimodal scene processing in real-world environments. We publish our stimulus scenes as spherical video recordings and sound field recordings in a publicly available database.

Alcohol ignition interlocks in all new vehicles: a broader perspective.

OBJECTIVE: To discuss the implications of widespread implementation of alcohol ignition interlocks. METHOD: We base our discussion on data from Finland including crash statistics and surveys collected from criminal justice professionals and general driving population. RESULTS: Alcohol ignition interlocks are an effective preventive measure against drunk driving when installed in the vehicles of convicted drunk drivers. However, once they are removed from the vehicles, drivers typically return to their habit of drinking and driving. Furthermore, for a number of reasons, the proportion of convicted drunk drivers that install an interlock in their vehicles is quite small. Therefore, many stakeholders believe that the solution to the drunk driving problem will come when interlocks become standard equipment in all new vehicles. However, drunk driving is a complex sociopsychological problem, and technology can rarely offer a solution to such complex problems. Consequently, many aspects of such interventions might be difficult to identify and include in cost-benefit analysis. CONCLUSION: We express caution about requiring an interlock as standard equipment in all new vehicles.

Concurrent explanations can enhance visual decision making.

The verbalization of one's thoughts has been shown to impair judgment and decision making in some cases, particularly when targets are perceptual. This finding has been attributed to the fact that non-verbal processes are sometimes difficult to verbalize, which may cause a shift in processing that is maladaptive to the task. The study shows that concurrent written explanations can also enhance judgment and decision making in certain visual choice tasks. This finding suggests that the effect of verbalization on perceptual tasks is not dependent on whether the targets of the judgment are verbal or perceptual but rather on whether there is adequate vocabulary to execute the task and whether the task benefits from a more analytic approach.

Night work, fatigued driving and traffic law: the case of police officers.

Given the well-known difficulties in defining and detecting fatigue, it is a real challenge to incorporate it into either traffic or criminal law. Finnish traffic law forbids fatigued driving "only" on a general level concerning the driver's fitness to drive. We present several comments from Finnish traffic and local police officers regarding their own experiences of driving while fatigued. The comments were extracted from a larger survey of traffic (N=129) and local (N=100) police officers, and prosecutors (N=96). Although the main topic of the survey was the application of the law that forbids fatigued driving, some police officers raised the issue of their own behavior in this respect. We argue that many shift workers, including police officers, break the law, especially when driving home after a night shift.

Convicted of fatigued driving: who, why and how?

Fatigue is a major cause of road traffic accidents. However, due to the blurred concept of fatigue and the lack of reliable testing devices (cf. the breath analyzer for alcohol levels), it is extremely difficult to incorporate fatigue in operationalized terms into either traffic or criminal law. Even though the Finnish Road Traffic Act explicitly forbids driving while tired, it is done only on a general level among other factors (sickness, etc.) that impair a driver's fitness to drive (Article 63). The present study was done to investigate the circumstances of fatigue driving offenses. From the Finnish Vehicle Administration driver record database we extracted all drivers (N=768) punished under Article 63 from 2004-2005. Of these drivers, 90.4% committed a fatigue-related traffic offense. Accidents, predominantly single vehicle, were the most common (92.5%) consequence of fatigued driving. Although fatigue-related accidents are thought to be serious, our data shows that most of the accidents (81.6%) did not involve personal injuries. Almost every twentieth driver was punished because his vehicle was drifting on the road. The presence of alcohol or drugs was noted in 13% of the cases. Only 3.1% of the punished drivers officially denied being tired or falling asleep. Young men (< or =35 yrs) represented 50% of all punished drivers. Time of day and seasonal effects were clear in this data. This study shows that even without a reliable fatigue detector and unambiguous criteria for recognizing the contribution of fatigue to accident causation, Finnish police and the courts punish a significant number of drivers every year on the basis of fatigue.

Fell asleep and caused a fatal head-on crash? A case study of multidisciplinary in-depth analysis vs. the court.

OBJECTIVES: Recognizing road accidents as sleep/fatigue-related is a challenging task due to the lack of validated criteria and reliable devices (cf. breath analyzer for alcohol levels). Consequently, it is difficult to incorporate fatigue in operationalized terms into either traffic or criminal law. Finnish Road Traffic Act explicitly forbids driving while tired but only on a general level regarding the driver's fitness to drive. The aim was to explore and compare the discussions held and conclusions reached by multidisciplinary accident-investigation teams and Finnish courts. METHODS: We describe nine fatal head-on crashes in which, according to the multidisciplinary investigation teams, the guilty nonintoxicated surviving driver had fallen asleep and caused the death of an occupant in the other vehicle. RESULTS: Despite the obvious difficulties with the data collection, the investigation teams provided sufficient information and explanation as to why falling asleep was the most probable cause of these nine accidents. On the other hand, there was wide variation in the court discussions and decisions. The court extensively deliberated on the role of fatigue in the four cases and only one driver was charged under the article of the Road Traffic Act covering driver fatigue. CONCLUSIONS: In conclusion, this study illustrates difficulties in enforcing the law that forbids driving while tired. Although multidisciplinary investigation teams analyze fatal accidents for safety-research purposes, and have a wider degree of freedom when making their conclusions, we believe that such expert evidence would be beneficial to the courts when they consider similar cases.

Fatal road accidents among Finnish military conscripts: fatigue-impaired driving.

The aims of the present study were to determine the current prevalence of personal car usage for holiday trips among Finnish conscripts and to analyze conscripts' fatal road accidents. The data included questionnaire data collected from 259 young conscripts at a garrison in southeastern Finland and data on 46 fatal road accidents caused by conscripts during the years 1991-2004, extracted from the national database of fatal road accidents studied in depth. The questionnaire data showed that one-third (35.9%) of young Finnish conscripts had used personal cars to travel to or from the garrison in the preceding 2 months. More than one-half of them reported driving while fatigued (a majority reported several occasions of such driving). In addition to those driving themselves, 41.6% of the conscripts rode at least occasionally as a passenger in a car driven by a fellow conscript. Analysis of the fatality data showed that one-half of the conscripts' fatal accidents occurred on the way to or from the garrison or while on duty. Falling asleep was the main cause of all conscripts' accidents (34.8%), with the largest proportion occurring when departing for leave (42.9%). Haste (including speeding) was the second greatest factor contributing to accidents occurring on the way to or from the garrison (26.1%), whereas drunk driving (22.7%) and suspected suicides (18.2%) were typical of accidents occurring on leave.

Seasonal variation of falling asleep while driving: An examination of fatal road accidents.

Road accidents related to sleep show a clear time-of-day pattern. Following the previous finding that such accidents in Finland happen more often (absolutely and relatively) during the summer months, especially during the afternoon, the main aim of this study was to reveal the factors behind such seasonality. The data included the computerized database of the Finnish fatal road accident investigation system restricted to nonprofessional, non-intoxicated car drivers (N=1464) and sample of the original folders (N=101). The results of the analysis on the sample of the original folders showed that investigation teams adequately documented and explained their decisions concerning falling-asleep accidents and that the observed seasonality is a real phenomenon, not a result of bias of the teams. With the exception of 26-35-year-olds, men of all of the other age groups had a notable absolute and relative increase of sleep-related accidents in the summer. Young male drivers (< or =25 yrs), followed by the oldest group (> or =66 yrs) had the highest increase in the absolute number of sleep-related accidents between the summer and winter months, while the relative change was the highest for ages 56-65. Women showed similar trends. A detailed analysis of 44 cases of summer afternoon falling-asleep accidents revealed that many drivers were engaged in unusual activities the day or night before the accident. The findings are discussed in relation to different driving and lifestyle habits between seasons, including sleep quality. Preliminary results of this study were presented at the 17th Congress of the European Sleep Research Society, Prague 2004.