Cannabis effects on driving longitudinal control with and without alcohol.

Although evidence suggests cannabis impairs driving, its driving-performance effects are not fully characterized. We aimed to establish cannabis' effects on driving longitudinal control (with and without alcohol, drivers' most common drug combination) relative to psychoactive ∆(9) -tetrahydrocannabinol (THC) blood concentrations. Current occasional (≥1×/last 3 months, ≤3 days per week) cannabis smokers drank placebo or low-dose alcohol, and inhaled 500 mg placebo, low (2.9%), or high (6.7%) THC vaporized cannabis over 10 min ad libitum in separate sessions (within-subject, six conditions). Participants drove (National Advanced Driving Simulator, University of Iowa) simulated drives 0.5-1.3 h post-inhalation. Blood and breath alcohol samples were collected before (0.17 and 0.42 h) and after (1.4 and 2.3 h) driving. We evaluated the mean speed (relative to limit), standard deviation (SD) of speed, percent time spent >10% above/below the speed limit (percent speed high/percent speed low), longitudinal acceleration, and ability to maintain headway relative to a lead vehicle (headway maintenance) against blood THC and breath alcohol concentrations (BrAC). In N=18 completing drivers, THC was associated with a decreased mean speed, increased percent speed low and increased mean following distance during headway maintenance. BrAC was associated with increased SD speed and increased percent speed high, whereas THC was not. Neither was associated with altered longitudinal acceleration. A less-than-additive THC*BrAC interaction was detected in percent speed high (considering only non-zero data and excluding an outlying drive event), suggesting cannabis mitigated drivers' tendency to drive faster with alcohol. Cannabis was associated with slower driving and greater headway, suggesting a possible awareness of impairment and attempt to compensate. Copyright © 2016 John Wiley & Sons, Ltd.

Cannabis effects on driving lateral control with and without alcohol.

BACKGROUND: Effects of cannabis, the most commonly encountered non-alcohol drug in driving under the influence cases, are heavily debated. We aim to determine how blood Δ(9)-tetrahydrocannabinol (THC) concentrations relate to driving impairment, with and without alcohol. METHODS: Current occasional (≥1×/last 3 months, ≤3days/week) cannabis smokers drank placebo or low-dose alcohol, and inhaled 500mg placebo, low (2.9%)-THC, or high (6.7%)-THC vaporized cannabis over 10min ad libitum in separate sessions (within-subject design, 6 conditions). Participants drove (National Advanced Driving Simulator, University of Iowa) simulated drives (∼0.8h duration). Blood, oral fluid (OF), and breath alcohol samples were collected before (0.17h, 0.42h) and after (1.4h, 2.3h) driving that occurred 0.5-1.3h after inhalation. We evaluated standard deviations of lateral position (lane weave, SDLP) and steering angle, lane departures/min, and maximum lateral acceleration. RESULTS: In N=18 completers (13 men, ages 21-37years), cannabis and alcohol increased SDLP. Blood THC concentrations of 8.2 and 13.1µg/L during driving increased SDLP similar to 0.05 and 0.08g/210L breath alcohol concentrations, the most common legal alcohol limits. Cannabis-alcohol SDLP effects were additive rather than synergistic, with 5µg/L THC+0.05g/210L alcohol showing similar SDLP to 0.08g/210L alcohol alone. Only alcohol increased lateral acceleration and the less-sensitive lane departures/min parameters. OF effectively documented cannabis exposure, although with greater THC concentration variability than paired blood samples. CONCLUSIONS: SDLP was a sensitive cannabis-related lateral control impairment measure. During drive blood THC ≥8.2µg/L increased SDLP similar to notably-impairing alcohol concentrations. Despite OF's screening value, OF variability poses challenges in concentration-based effects interpretation.

The effects of age and workload on 3D spatial attention in dual-task driving.

In the present study we assessed whether the limits in visual-spatial attention associated with aging affect the spatial extent of attention in depth during driving performance. Drivers in the present study performed a car-following and light-detection task. To assess the extent of visual-spatial attention, we compared reaction times and accuracy to light change targets that varied in horizontal position and depth location. In addition, because workload has been identified as a factor that can change the horizontal and vertical extent of attention, we tested whether variability of the lead car speed influenced the extent of spatial attention for younger or older drivers. For younger drivers, reaction time (RT) to light-change targets varied as a function of distance and horizontal position. For older drivers RT varied only as a function of distance. There was a distance by horizontal position interaction for younger drivers but not for older drivers. Specifically, there was no effect of horizontal position at any given level of depth for older drivers. However, for younger drivers there was an effect of horizontal position for targets further in depth but not for targets nearer in depth. With regards to workload, we found no statistically reliable evidence that variability of the lead car speed had an effect on the spatial extent of attention for younger or older drivers. In a control experiment, we examined the effects of depth on light detection when the projected size and position of the targets was constant. Consistent with our previous results, we found that drivers' reaction time to light-change targets varied as a function of distance even when 2D position and size were controlled. Given that depth is an important dimension in driving performance, an important issue for assessing driving safety is to consider the limits of attention in the depth dimension. Therefore, we suggest that future research should consider the importance of depth as a dimension of spatial attention in relation to the assessment of driving performance.

Multisensory integration, aging, and the sound-induced flash illusion.

The present study examined age-related differences in multisensory integration and the role of attention in age-related differences in multisensory integration. The sound-induced flash illusion--the misperception of the number of visual flashes due to the simultaneous presentation of a different number of auditory beeps--was used to examine the strength of multisensory integration in older and younger observers. The effects of integration were examined when discriminating 1-3 flashes, 1-3 beeps, or 1-3 flashes presented with 1-3 beeps. Stimulus conditions were blocked according to these conditions with baseline (unisensory) performance assessed during the multisensory block. Older participants demonstrated greater multisensory integration--a greater influence of the beeps when judging the number of visual flashes--than younger observers. In a second experiment, the role of attention was assessed using a go/no-go paradigm. The results of Experiment 2 replicated those of Experiment 1. In addition, the strength of the illusion was modulated by the sensory domain of the go/no-go task, though this did not differ by age group. In the visual go/no-go task we found a decrease in the illusion, yet in the auditory go/no-go task we found an increase in the illusion. These results demonstrate that older individuals exhibit increased multisensory integration compared with younger individuals. Attention was also found to modulate the strength of the sound-induced flash illusion. However, the results also suggest that attention was not likely to be a factor in the age-related differences in multisensory integration.

Standardized Beck Depression Inventory-II scores for male veterans coping with chronic pain.

The Beck Depression Inventory II (BDI-II) has been suspected of overestimating the level of depression in individuals that endure chronic pain. Using a sample (N = 345) of male military veterans with chronic pain enrolled in an outpatient treatment program, a factor analysis on the BDI-II revealed a "Somatic Complaints" factor along with 2 other factors we labeled "Negative Rumination" and "Mood." Standardized scores were provided for each BDI-II factor score, Total score, and Total minus Somatic score. The internal consistency reliabilities (Gilmer-Feldt and alpha coefficients) for all scores were found to be clinically acceptable. Item-Total score correlations found that all of the BDI-II items were good discriminators (r > .30). We conclude that the normative data provided in this study should help control for somatic responding by male chronic pain veterans on the BDI-II. We highly recommend that clinicians and researchers use the norm-referenced method when interpreting BDI-II scores from individuals suffering from chronic pain.

Detection of 3D curved trajectories: the role of binocular disparity.

We examined the ability of observers to detect the 3D curvature of motion paths when binocular disparity and motion information were present. On each trial, two displays were observed through shutter-glasses. In one display, a sphere moved along a linear path in the horizontal and depth dimensions. In the other display, the sphere moved from the same starting position to the same ending position as in the linear path, but moved along an arc in depth. Observers were asked to indicate whether the first or second display simulated a curved trajectory. Adaptive staircases were used to derive the observers' thresholds of curvature detection. In the first experiment, two independent variables were manipulated: viewing condition (binocular vs. monocular) and type of curvature (concave vs. convex). In the second experiment, three independent variables were manipulated: viewing condition, type of curvature, and whether the motion direction was approaching or receding. In both experiments, detection thresholds were lower for binocular viewing conditions as compared to monocular viewing conditions. In addition, concave trajectories were easier to detect than convex trajectories. In the second experiment, the direction of motion did not significantly affect curvature detection. These results indicate the detection of curved motion paths from monocular information was improved when binocular information was present. The results also indicate the importance of the type of curvature, suggesting that the rate of change of disparity may be important in detecting curved trajectories.

The effect of SPAM administration during a dynamic simulation.

OBJECTIVE: The objective of this study was to determine whether administration of the situation present assessment method (SPAM) affects workload and/or task performance. BACKGROUND: SPAM probes are thought to isolate workload from the assessment of situation awareness (SA) by including a warning signal before asking an SA-related question. However, there is a good reason to think that SPAM may still have an effect on dynamic workload and task performance. Specifically, nearly all dual tasks affect workload and performance; thus, it would be surprising if SPAM did not. METHOD: Following the methods of Durso, Bleckley, and Dattel, I evaluated workload and performance on the Air Traffic Scenarios Test in SPAM, non-SPAM probe, and no-probe conditions. RESULTS: Global workload was unaffected by probe administration. However, at least with novice performers, SPAM probes affected task performance. CONCLUSION: The use of a warning signal does not eliminate performance decrements associated with secondary tasks. Moreover, there may be performance decrements unique to SPAM. APPLICATION: Cautious users of online assessment measures, such as SPAM, may want to remove performance immediately subsequent to probes from analysis, use an interprobe interval longer than 2.83 min, and construct their assessment measures to reduce display search times unrelated to primary task performance.

Using multisensory cues to facilitate air traffic management.

OBJECTIVE: In the present study, we sought to investigate whether auditory and tactile cuing could be used to facilitate a complex, real-world air traffic management scenario. BACKGROUND: Auditory and tactile cuing provides an effective means of improving both the speed and accuracy of participants' performance in a variety of laboratory-based visual target detection and identification tasks. METHOD: A low-fidelity air traffic simulation task was used in which participants monitored and controlled aircraft.The participants had to ensure that the aircraft landed or exited at the correct altitude, speed, and direction and that they maintained a safe separation from all other aircraft and boundaries. The performance measures recorded included en route time, handoff delay, and conflict resolution delay (the performance measure of interest). In a baseline condition, the aircraft in conflict was highlighted in red (visual cue), and in the experimental conditions, this standard visual cue was accompanied by a simultaneously presented auditory, vibrotactile, or audiotactile cue. RESULTS: Participants responded significantly more rapidly, but no less accurately, to conflicts when presented with an additional auditory or audiotactile cue than with either a vibrotactile or visual cue alone. CONCLUSION: Auditory and audiotactile cues have the potential for improving operator performance by reducing the time it takes to detect and respond to potential visual target events. APPLICATION: These results have important implications for the design and use of multisensory cues in air traffic management.

Pursuing happiness in everyday life: the characteristics and behaviors of online happiness seekers.

Although the last decade has witnessed mounting research on the development and evaluation of positive interventions, investigators still know little about the target population of such interventions: happiness seekers. The present research asked three questions about happiness seekers: (1) What are their general characteristics?, (2) What do they purposefully do to become happier?, and (3) How do they make use of self-help resources? In Study 1, we identified two distinct clusters of online happiness seekers. In Study 2, we asked happiness seekers to report on their use of 14 types of happiness-seeking behaviors. In Study 3, we tracked happiness seekers' usage of an iPhone application that offered access to eight different happiness-increasing activities, and assessed their resulting happiness and mood improvements. Together, these studies provide a preliminary portrait of happiness seekers' characteristics and naturalistic behaviors.

Anticipatory baseline effects and information integration in visual world studies.

Researchers often conduct visual world studies to investigate how listeners integrate linguistic information with prior context. Such studies are likely to generate anticipatory baseline effects (ABEs), differences in listeners' expectations about what a speaker might mention that exist before a critical speech stimulus is presented. ABEs show that listeners have attended to and accessed prior contextual information in time to influence the processing of the critical speech stimulus. However, further evidence is required to show that the information actually did influence subsequent processing. ABEs can compromise the validity of inferences about information integration if they are not appropriately controlled. We discuss four solutions: statistical estimation, experimental control, elimination of "on-target" trials, and neutral gaze. An experiment compares the performance of these solutions, and suggests that the elimination of on-target trials introduces bias in the direction of ABEs, due to the statistical phenomenon of regression toward the mean. We conclude that statistical estimation, possibly coupled with experimental control, offers the most valid and least biased solution.

The role of working memory in the metaphor interference effect.

Participants took longer to judge that metaphors (e.g., an insult is a razor, memory is a warehouse) were literally false than to judge that scrambled sentences (e.g., an insult is a warehouse) were false. This result is the metaphor interference effect (MIE). It demonstrates that metaphor processing is automatic. In this experiment, we found that the magnitude of the MIE is predicted by working memory (WM) capacity, with higher WM yielding a smaller MIE. This suggests that although metaphor comprehension is automatic, the early processing of metaphors is controllable by executive mechanisms. We relate our results to Kintsch's (2000, 2001) predication model. Specifically, we suggest that mechanisms of WM influence metaphor processing by affecting the effectiveness of the construction-integration process that identifies common properties between topics and vehicles. WM also influences the speed with which meanings are identified as literal or figurative.