Friendly Fire and the Sustained Attention to Response Task

Prolonging the Response Movement Reduces Commission Errors in a High-Go, Low-No-Go Target Detection Task and Composite Metrics of Performance Miss This Effect

OBJECTIVE

Expand research on the Sustained Attention to Response Task (SART) to a more applied agricultural target detection/selection task and examine the utility of various performance metrics, including composite measures of speed and accuracy, in a High-Go/Low-No-Go stimuli task.

BACKGROUND

Modified SARTs have been utilized to investigate mechanisms, such as failures of response inhibition, occurring in friendly fire and collateral damage incidents. Researchers have demonstrated that composite measures of speed and accuracy are useful for Low Go/High No-Go stimuli tasks, but this has not been demonstrated for High-Go/Low-No-Go tasks, such as the SART.

METHOD

Participants performed a modified SART, where they selected ("sprayed") images of weeds (Go stimuli) that appeared on a computer screen, while withholding to rarer soybean plant images (No-Go stimuli).

RESULTS

Response time was a function of distance from a central starting point. Participants committed commission errors (sprayed the soybeans) at a significantly higher rate when the stimuli appeared under the cursor centered on the screen for each trial. Participant's omission errors (failure to spray a weed) increased significantly as a function of distance. The composite measures examined were primarily influenced by response time and omission errors limiting their utility when commission errors are of particular interest.

CONCLUSION

Participants are far more accurate in their decision making when required to execute a longer duration motor task in High-Go/Low-No-Go experiments.

APPLICATION

Demonstrates a serious human factors liability of target detection and snap-to-target systems.

Perceptual decoupling or trigger happiness: the effect of response delays and shorter presentation times on a go-no-go task with a high go prevalence

In the current investigation, we modified the high Go, low No-Go Sustained Attention to Response Task (SART). Some researchers argue a commission error, an inappropriate response to a No-Go stimulus, in the SART is due to the participant being inattentive, or perceptually decoupled, during stimulus onset. Response delays in the SART reduce commission errors. A response delay may therefore enable a participant who is initially inattentive to recouple their attention in time to appropriately perceive the stimulus and withhold a response to a No-Go stimulus. However, shortening stimulus display duration in the SART should limit the possibility of the participant identifying the stimulus later, if they are initially not attending the stimulus. A response delay should not reduce commission errors if stimulus duration is kept to the minimum duration enabling stimulus recognition. In two experiments, we shortened stimulus onset to offset duration and added response delays of varying lengths. In both experiments, even when stimulus duration was shortened, response delays notably reduced commission errors if the delay was greater than 250 ms. In addition, using the Signal Detection Theory perspective in which errors of commission in the SART are due to a lenient response bias-trigger happiness, we predicted that response delays would result in a shift to a more conservative response bias in both experiments. These predictions were verified. The errors of commission in the SART may not be a measures of conscious awareness per se, but instead indicative of the level of participant trigger happiness-a lenient response bias.

A combined experimental-correlational approach to the construct validity of performance-based and self-report-based measures of sustained attention

The ability to sustain attention is often measured with either objective performance indicators, like within-person RT variability, or subjective self-reports, like mind wandering propensity. A more construct valid approach, however, may be to assess the covariation in these performance and self-report measures, given that each of these is influenced by different sources of measurement error. If the correlation between performance-variability and self-report measures reflects the sustained attention construct, then task manipulations aimed at reducing the sustained attention demands of tasks should reduce the correlation between them (in addition to reducing mean levels of variability and mind wandering). The current study investigated this claim with a combined experimental-correlation approach. In two experiments (Ns ~ 1,500 each), participants completed tasks that either maximized or minimized the demand for sustained attention. Our demand manipulations successfully reduced the mean levels of sustained attention failures in both the objective and subjective measures, in both experiments. In neither experiment, however, did the covariation between these measures change as a function of the sustained attention demands of the tasks. We can therefore claim only minimal support for the construct validity of our measurement approach to sustained attention.

Cognitive Performance changes during a 20-day Winter Military Training Course and the Following 10-day Recovery Period

Introduction: The purpose of the present study was to investigate the effects of a winter military field training course consisting of strenuous physical stressors (e.g. physical activity, sleep deprivation and cold weather) on cognitive performance among Finnish soldiers.Methods: Fifty-eight (age 19 ± 1 years, height 182 ± 6 cm, body mass 78.5 ± 7.2 kg) male soldiers took part in a 20-day military field training course in northern Finland. Cognitive performance was assessed before, during, and after the course four times on a tablet computer. Sustained Attention to Response Task (SART) was used to assess soldier's executive and inhibitory function. Baddeley's 3-min reasoning task (BRT) was used to assess grammatical reasoning, and Change Blindness (CB) task was used to assess visual perception.Results: Strenuous winter field training had detrimental effects in all performance tests compared to baseline. SART response rate decreased 27.3% (p < 0.001), and BRT and CB task scores decreased 20.6% (p < 0.01) and 14.1% (p < .05), respectively.Conclusion: The present study showed a decline in soldier's cognitive performance after 20-days of physically demanding winter military field training. To be able to optimise field training, it is important to be aware of how cognitive performance changes during military exercises and missions.

Not according to plan: Cognitive failures in marksmanship due to effects of expertise, unknown environments, and the likelihood of shooting unintended targets

Shooting errors have multi-faceted causes with contributing factors that include sensorimotor activity and cognitive failures. Empirical investigations often assess mental errors through threat identification, yet other cognitive failures could contribute to poor outcomes. The current study explored several possible sources of cognitive failures unrelated to threat identification with live fire exercises. Experiment 1 examined a national shooting competition to compare marksmanship accuracy, expertise, and planning in the likelihood of hitting no-shoot or unintended targets. Experts demonstrated an inverse speed/accuracy trade-off and fired upon fewer no-shoot targets than lesser skilled shooters, yet overall, greater opportunity to plan produced more no-shoot errors, thereby demonstrating an increase in cognitive errors. Experiment 2 replicated and extended this finding under conditions accounting for target type, location, and number. These findings further dissociate the roles of marksmanship and cognition in shooting errors while suggesting that marksmanship evaluations should be re-designed to better incorporate cognitive variables.

Optimizing Performance and Mental Skills With Mindfulness-Based Attention Training: Two Field Studies With Operational Units

INTRODUCTION

Mental skills such as focusing attention and managing emotions are essential for optimal performance in high-stress occupations. Studies with military samples have demonstrated that mindfulness training (MT) led to improved computer-based cognitive performance.

MATERIALS AND METHODS

To examine the impact of MT on operational performance, mental skills, and psychological health, a short-form program, Mindfulness-Based Attention Training (MBAT), was delivered to active duty soldiers as part of two randomized trials. Participants in study 1 (n = 121) and study 2 (n = 77) were randomized to one of three conditions: MT with proctored practice, MT with unproctored practice, or a waitlist control. Weekly 2-hour MBAT sessions were offered to participants in both MT conditions for 4 weeks. Beyond these sessions, participants also engaged in mindfulness practice that was proctored (within the occupational context) or unproctored (left up to the individual) for four subsequent weeks.

RESULTS

Overall, the frequency of mindfulness practice was generally associated with better performance and improvements in mental skills. In study 1, those who practiced 3 or more days per week performed better on marksmanship under physical stress and reported fewer attentional lapses, less emotion regulation difficulties, greater mental toughness, and higher self-reported mindfulness compared to those who did not practice. In study 2, the frequency of mindfulness practice was associated with fewer attentional lapses and emotion regulation difficulties.

CONCLUSIONS

Consistent with prior findings, results suggest that regular engagement in MT practice may help to optimize operational performance and improve mental skills in military cohorts.

Go-stimuli probability influences response bias in the sustained attention to response task: a signal detection theory perspective

The sustained attention to response task (SART) is a popular measure in the psychology and neuroscience of attention. The underlying psychological cause for errors, in particular errors of commission, in the SART is actively disputed. Some researchers have suggested task-disengagement due to mind-wandering or mindlessness, and others have proposed strategic choices. In this study we explored an alternative perspective based on Signal Detection Theory, in which the high rate of commission errors in the SART reflects simply a shift in response bias (criterion) due to the high prevalence of Go-stimuli. We randomly assigned 406 participants to one of ten Go-stimuli prevalence rates (50%, 64%, 74%, 78%, 82%, 86%, 90%, 94%, 98% and 100%). As Go-stimuli prevalence increased reaction times to both Go and No-Go stimuli decreased, omission errors decreased and commission errors increased. These all were predicted from a hypothesized bias shift, but the findings were not compatible with some alternative theories of SART performance. These findings may have implications for similar tasks.

How speed impacts threat assessment in lethal force decisions

Despite the importance of being both fast and accurate in lethal force decisions, there is little empirical evidence to identify how speed impacts threat-related decisions and perception. Two experiments used speeded and unspeeded manipulations to determine how the speed imperative impacted threat assessments. Experiment 1 used drift diffusion modeling to quantify decision parameters, including rate of information processing, decision threshold, bias, and non-decisional processes. Speeded conditions reduced the information threshold needed to make decisions and shortened non-decisional processes, yet this manipulation had no impact on the rate of information processing or starting bias. Experiment 2 explored perceptual differences in threat assessment. Participants confidently made threat assessments despite only 30 ms exposure to stimuli with little impact on their subjective threat ratings based on exposure duration. Taken together, these results document the influence of speed on decision-making parameters of threat assessments while demonstrating little impact on threat perception.

Perception Over Personality in Lethal Force: Aggression, Impulsivity, and Big Five Traits in Threat Assessments and Behavioral Responses due to Weapon Presence and Posture

The use of lethal force is a combination of threat perception and individual judgment that sometimes warrants a behavioral response. This simplified description implicates perceptual factors and individual differences in lethal force decision making, which ongoing research continues to address. However, personality-based factors have been less explored as to how they might affect either threat perception or behavioral responses in a lethal force decision. The current investigation examined multiple personality traits with the potential to influence lethal force decision making, including aggression, impulsivity, and the Big Five traits. These measures were compared to threat perception and behavioral responses made to a variety of lethal force stimuli broadly categorized as clear threats, ambiguous threats, and clear nonthreats. Samples were recruited from combat-trained infantry, military recruits, and the civilian community to control for prior lethal force training. Although there was a strong omnibus relationship between threat perception and the likelihood of a behavioral response, neither military training nor personality differences had any impact on threat perception or a binary (e.g., shoot/don't-shoot) behavioral response. Therefore, we conclude that perception dominates personality in lethal force decision making when the threat assessment decision is limited to factors such as weapon presence or posture rather than emotion.

Measuring Lethal Force Performance in the Lab: The Effects of Simulator Realism and Participant Experience

OBJECTIVE

The goal of the current study was to compare two types of shooting simulators to determine which is best suited for assessing different aspects of lethal force performance.

BACKGROUND

Military and law enforcement personnel are often required to make decisions regarding the use of lethal force. A critical goal of both training and research endeavors surrounding lethal force is to find ways to simulate lethal force encounters to better understand behavior in those scenarios.

METHOD

Participants of varying degrees of experience completed both marksmanship and shoot/don't shoot scenarios on both a video game and a military-grade shooting simulator. Using signal detection theory, we assessed sensitivity as a measure of lethal force performance overall. We used hit rate to assess shooting accuracy and false alarm rate to assess decision making.

RESULTS

Results demonstrated that performance was correlated across simulators. Results supported the notion that shooting accuracy and decision making are independent components of performance. Individuals with firearms expertise outperformed novices on the military-grade simulator, but only with respect to shooting accuracy, not unintended casualties. Individuals with video game experience outperformed novices in the video game simulator, but again only on shooting accuracy.

CONCLUSION

Experience played a crucial role in the assessment of shooting accuracy on a given simulator platform; decision-making performance remained unaffected by experience level or type of simulator.

APPLICATION

We recommend that in expert populations or when assessing shooting accuracy, a military-grade shooting simulator be used. However, with a novice population and/or when interested in decision making in lethal force, a video game simulator is appropriate.

The effects of real-time performance feedback and performance emphasis on the sustained attention to response task (SART)

The sustained attention to response task (SART) has been used for over 20 years to assess participants' response times and inability to withhold to No-Go stimuli (commission errors). While there is debate in the literature regarding what causes commissions errors in the SART, there is agreement the SART is subject to a speed-accuracy trade-off (SATO). Researchers have demonstrated that performance on the SART can be influenced by directive instructions to participants to prioritize either speed or accuracy during the task. In the present study, we investigated whether real-time performance feedback and whether feedback emphasis (emphasizing speed or accuracy) affected participants' response times and accuracy. We found performance feedback per se had no impact on performance, but performance emphasis did affect performance, apparently shifting the SATO. This finding provides further evidence that the commission errors in the SART are not indicative of sustained attention or vigilance as those terms are commonly used in the literature, but more likely assess response strategy and motor control (or lack of motor control). These findings have implications for the psychological assessment literature, as well as applied areas where SART findings have been utilized such as shoot/no-shoot decision making.

The role of inhibitory control in shoot/don't-shoot decisions

Previous work has demonstrated a link between cognitive abilities, specifically inhibitory control and lethal force decision-making performance. However, many previously used approaches to simulating shoot/don't shoot scenarios have lacked ecological validity. There is a need to investigate how inhibitory control impacts shoot/don't decisions using realistic simulations to better translate the findings to military and law enforcement settings. This study used multiple cognitive control tasks incorporating discrete judgements in go/no-go and stop signal tasks as well as subjective judgements in go/no-go tasks with both colour stimuli and emotional faces. These combined tasks provided a comprehensive evaluation of inhibitory control abilities. To ensure ecological validity in shooting performance, existing military training scenarios incorporated realistic weaponry and aiming behaviours across different shoot/don't-shoot simulations. The inhibitory control battery identified five principal components from the various tasks, including: stopping ability, response speed, emotion detection, colour detection, and emotional biases. These principal inhibitory control components were entered into hierarchical linear regressions with the dependent variables of unintended casualties inflicted and lethal rounds fired, respectively. Stopping ability better predicted the likelihood of inflicting an unintended casualty, whereas response speed better predicted the number of lethal rounds fired. These regression models included baseline metrics of marksmanship and shots fired, which supports a role for inhibitory control above and beyond basic shooting abilities or strategy. These collective findings provide mechanistic support for the relationship between inhibitory control and errors in shoot/don't-shoot decision-making while using realistic military training scenarios.

How unintentional cues can bias threat assessments during shoot/don't-shoot simulations

OBJECTIVE

Identify whether contextual information may unintentionally alter decision-making during lethal force training.

BACKGROUND

Lethal force decisions inherently involve a threat assessment, where an individual learns to identify a threat and use force commensurate to the situation. This decision is ultimately subject to numerous cognitive influences, particularly during training where artificial factors may bias decision-making.

METHOD

Participants made threat assessments for tasks that presented hostile stimuli (pointing guns) and non-hostile stimuli (holding cell phones). Experiment 1 identified issues in target design by applying scoring rings as cues to targets, whereas Experiment 2 used bullet holes to assess cues due to target reuse. Experiment 3 applied these cues equally to hostile and non-hostile stimuli to prevent a predictive relationship from forming.

RESULTS

Significant cueing effects were observed in both Experiments 1 and 2. For Experiment 3, response times were not impacted by the invalid cues as participants could no longer reliably use the cue to distinguish between hostile and non-hostile stimuli.

CONCLUSION

Stimulus-related factors can unintentionally create predictive relationships during lethal force training. These predictive factors are problematic because they allow participants to make threat assessments during training in a way that would never be realistic in the field.

APPLICATION

Modifications should be made to hostile and non-hostile targets in equal measure to avoid creating an unintentionally predictive relationship that identifies hostile targets. In practice, scoring rings and bullet holes should be added to non-hostile stimuli to better parallel hostile stimuli.

Perceptual and response factors in the gradual onset continuous performance tasks

Using a novel gradual onset continuous performance task (gradCPT), recent research has uncovered a brain network of the sustained attention ability, demonstrating marked individual differences. Yet much about the cognitive processes that support performance on the gradCPT remains unknown. Here, we tested the importance of response inhibition and perceptual discrimination in the gradCPT. Participants monitored a continuous stream of natural scenes from two categories-cities and mountains-with a 9:1 ratio. In separate task blocks, they responded either to the frequent or the rare, yielding a response rate of either 90% or 10%. Performance was much worse, and declined more significantly over time, when the required response rate was higher. To test the role of stimulus onset, separate task blocks presented the scenes either gradually, with adjacent scenes blending into each other (gradCPT), or abruptly, with a single scene visible at a time (abruptCPT). Despite its increased complexity, the gradCPT yielded better performance than the abruptCPT, contradicting the perceptual complexity hypothesis and suggesting a detrimental role of the automaticity of responses to rhythmic stimuli in sustained attention. Further bolstering the role of response inhibition in the gradCPT, participants with superior inhibitory function, as assessed by the "stop-signal" task, did better on the gradCPT. These findings show that response inhibition contributes to the ability to sustain attention, especially in tasks that require frequent and repetitive responses as in assembly-line jobs.

Developing scenarios that evoke shoot/don't-shoot errors

Multiple errors can occur in a use-of-force scenario, although some critical errors involve unintended casualties where the target should never have been fired upon. Training instructors utilize a variety of methods to ensure military and law enforcement personnel do not inflict unintended casualties. However, there is little empirical evidence about the best methods to design a shooting simulation that might evoke these errors, which is critical to ensure the validity of any assessment or training exercise. The current study analyzed performance across a variety of simulated shooting scenarios developed and applied for military training purposes. Several factors were assessed based upon either the scenario or human performance. Scenario type, number of shots fired, and the ratio of hostiles-to-non-hostiles were significant predictors for the likelihood of inflicting an unintended casualty. This collected evidence should help improve scenario design for future training simulations that will help avoid these critical shooting errors.

Perception during use of force and the likelihood of firing upon an unarmed person

Stress can impact perception, especially during use-of-force. Research efforts can thus advance both theory and practice by examining how perception during use-of-force might drive behavior. The current study explored the relationship between perceptual judgments and performance during novel close-combat training. Analyses included perceptual judgments from close-combat assessments conducted pre-training and post-training that required realistic use-of-force decisions in addition to an artificially construed stress-inoculation event used as a training exercise. Participants demonstrated significant reductions in situational awareness while under direct fire, which correlated to increased physiological stress. The initial likelihood of firing upon an unarmed person predicted the perceptual shortcomings of later stress-inoculation training. Subsequently, likelihood of firing upon an unarmed person was reduced following the stress-inoculation training. These preliminary findings have several implications for low or zero-cost solutions that might help trainers identify individuals who are underprepared for field responsibilities.

When the response does not match the threat: The relationship between threat assessment and behavioural response in ambiguous lethal force decision-making

Deciding when to use lethal force inherently depends on assessing threat, a process that itself incorporates numerous perceptual factors. This study assessed this relationship between perception-based threat assessment and behaviour-based threat response. Specifically, participants completed multiple tasks designed to elicit either a threat rating (e.g., perception-informed threat assessment) or a binary behavioural response (e.g., shoot/don't-shoot). Actor posture and weapon presence significantly affected the threat assessment, which was an extremely powerful omnibus predictor of threat response. However, for ambiguous threat stimuli, perceived threat became a poor predictor for threat response relative to the omnibus test. Participants appeared to adopt additional rules to inform behaviour independent of the threat assessment when faced with an ambiguous situation. These results demonstrate an intriguing disparity between subjective threat assessment and the behavioural response to use force that does not apply well to ambiguous cases or adequately explain errors in lethal force decisions.

Response Complexity Reduces Errors on a Response Inhibition Task

OBJECTIVE

The purpose of this investigation was to elucidate the role of button-response complexity to targets in a response inhibition task.

BACKGROUND

Response inhibition is the ability to correctly inhibit an overt response to a target. The U.S. military is actively pursuing development of armed, combat robots as a force multiplier, which may present challenges to operators of combat robots in the form of response inhibition errors.

METHOD

A total of 15 participants completed two 51-min versions of a modified sustained attention to response task (SART). Participants were outfitted with an electrocardiogram to index heart-rate variability and completed the NASA-Task Load Index (NASA-TLX) to index workload.

RESULTS

The results demonstrated that the complex SART reduced errors of commission (4%) and slowed response times (874 ms) to correct Go targets relative to the simple SART (14%, 739 ms). The NASA-TLX did not show differences between the modified SARTs; however, heart-rate variability did demonstrate that Soldiers had an increased autonomic stress response to the complex SART.

CONCLUSION

Increasing the behavioral response requirement during a response inhibition task can decrease errors of commission; however, it comes at the cost of slower response times to target stimuli. Heart-rate variability may provide better insight into objective workload relative to subjective measures.

APPLICATION

The use of complex behavioral responses may provide a viable option to reduce potential "friendly fire" or collateral damage by Soldiers remotely engaging a target-rich environment.

The quick and the dead: A paradigm for studying friendly fire

The Sustained Attention to Response Task (SART) is a computer based Go-No-Go response task. Participants respond to frequently occurring neutral stimuli and withhold responses to rare target stimuli. Researchers have suggested the inhibition demands of the SART may mirror those which occur in some firearm accidents. Participants in the present experiment used a simulated nonlethal weapon to subdue threats (images of people holding guns) on large screens. Participants completed a target rich task (high Go low No-Go, like a SART), a target sparse task (low Go/high No-Go), a verbal recall task, and dual versions of the target rich and target sparse tasks with the verbal recall task as the secondary task. Results provided further evidence that some accidental shootings may result from failures of response inhibition and that additional cognitive load is detrimental to overall performance. Future studies should explore the role of response inhibition in realistic firearm scenarios.

Mindfulness training as cognitive training in high-demand cohorts: An initial study in elite military servicemembers

Cognitive ability is a key selection criterion for entry into many elite professions. Herein, we investigate whether mindfulness training (MT) can enhance cognitive performance in elite military forces. The cognitive effects of a short-form 8-h MT program contextualized for military cohorts, referred to as Mindfulness-Based Attention Training (MBAT), were assessed. Servicemembers received either a 2-week (n=40) or 4-week (n=36) version of MBAT or no training (NTC, n=44). Sustained attention and working memory task performance along with self-reported cognitive failures were assessed at study onset (T1) and 8-weeks later (T2). In contrast to both the NTC and 2-week MT groups, the 4-week MT group significantly improved over time on attention and working memory outcome measures. Among the 4-week more so than the 2-week MBAT participants, working memory performance improvements were correlated with their amount of out-of-class MT practice. In addition to these group-wise effects, all participants receiving MBAT decreased in their self-reported cognitive failures from T1 to T2. Importantly, none of these improvements were related to self-reported task motivation. Together, these results suggest that short-form MT, when delivered over a 4-week delivery schedule, may be an effective cognitive training tool in elite military cohorts.

Prolonging the response movement inhibits the feed-forward motor program in the sustained attention to response task

Despite widespread use in clinical and experimental contexts, debate continues over whether or not the Sustained Attention to Response Task (SART) successfully measures sustained attention. Altering physical aspects of the response movement required to SART stimuli may help identify whether performance is a better measure of perceptual decoupling, or response strategies and motor inhibition. Participants completed a SART where they had to manually move a mouse cursor to respond to stimuli, and another SART where this extra movement was not required, as in a typical SART. Additionally, stimuli were located at either a close or a far distance away. Commission errors were inversely related to distance in the manual movement condition, as the farther distance led to longer response times which gave participants more time to inhibit prepotent responses and thus prevent commission errors. Self-reported measures of mental demand and fatigue suggested there were no differences in mental demands between the manual and automatic condition; instead the differences were primarily in physical demands. No differences were found for task-unrelated thoughts between the manual and automatic condition. The movement effect combined with participants' subjective reports are evidence for time dependent action stopping, not greater cognitive engagement. These findings support a response strategy perspective as opposed to a perceptual decoupling perspective, and have implications for authors considering using the SART. Applied implications of this research are also discussed.

Prior Mental Fatigue Impairs Marksmanship Decision Performance

Purpose: Mental fatigue has been shown to impair subsequent physical performance in continuous and discontinuous exercise. However, its influence on subsequent fine-motor performance in an applied setting (e.g., marksmanship for trained soldiers) is relatively unknown. The purpose of this study was to investigate whether prior mental fatigue influences subsequent marksmanship performance as measured by shooting accuracy and judgment of soldiers in a live-fire scenario.

Methods: Twenty trained infantry soldiers engaged targets after completing either a mental fatigue or control intervention in a repeated measure design. Heart rate variability and the NASA-TLX were used to gauge physiological and subjective effects of the interventions. Target hit proportion, projectile group accuracy, and precision were used to measure marksmanship accuracy. Marksmanship accuracy was assessed by measuring bullet group accuracy (i.e., how close a group of shots are relative to center of mass) and bullet group precision (i.e., how close are each individual shot to each other). Additionally, marksmanship decision accuracy (correctly shooting vs. correctly withholding shot) when engaging targets was used to examine marksmanship performance.

Results: Soldiers rated the mentally fatiguing task (59.88 ± 23.7) as having greater mental workload relative to the control intervention [31.29 ± 12.3, t₍₁₉₎ = 1.72, p < 0.001]. Additionally, soldiers completing the mental fatigue intervention (96.04 ± = 37.1) also had lower time-domain (standard deviation of normal to normal R-R intervals) heart rate variability relative to the control [134.39 ± 47.4, t₍₁₈₎ = 3.59, p < 0.001]. Projectile group accuracy and group precision failed to show differences between interventions [t₍₁₉₎ = 0.98, p = 0.34, t₍₁₉₎ = 0.18, p = 0.87, respectively]. Marksmanship decision errors significantly increased after soldiers completed the mental fatigue intervention (48% ± 22.4) relative to the control intervention [M = 32% ± 79.9, t₍₁₉₎ = 4.39, p < 0.001]. There was a significant negative correlation between shooting response time and errors of commission (r = −0.61; p = 0.004) when preceded by the mental fatigue intervention, but not the control (r = −0.31; p = 0.17).

Conclusion: The mental fatigue intervention was successful in eliciting fatigue which was supported subjectively and objectively. Marksmanship judgment performance is significantly reduced when soldiers are mentally fatigued, although shot accuracy is not.

Shooter-System Performance Variability as a Function of Recoil Dynamics

OBJECTIVE

The goal of this study was to quantify shooter performance relative to subtle variations in recoil energy.

BACKGROUND

Marksmanship performance remains undefined for subtle distinctions in weapon recoil energy across common small-arms platforms.

METHOD

Weapons were customized using multiple components and ammunition types. Firing scenarios were designed to examine the effect of recoil energy on shooter timing and accuracy.

RESULTS

The results suggest that recoil condition does not affect timing during firing sequences designed to elicit differences in timed-fire performance. Recoil condition did, however, influence shot placement, with accuracy decreasing as the energy associated with firing increased. Subjective recoil estimations were quantified according to relative magnitude and spatial distribution of perceived energy transferred at shooter-weapon surface contact locations.

CONCLUSION

The absence of differences in time to engage may be reflective of resistance to recoil-induced point-of-aim deviation based on experience. Distinctions in performance were revealed despite subtle differences in recoil energy between conditions. An instrument that may be sensitive to shooter perception of subtle differences in recoil energy during firing was also developed.

APPLICATION

The findings inform performance expectations for small-arms systems relative to recoil energy levels transferred to the shooter during dynamic firing events.

Target Detection and Identification Performance Using an Automatic Target Detection System

OBJECTIVE

We investigated the effects of automatic target detection (ATD) on the detection and identification performance of soldiers.

BACKGROUND

Prior studies have shown that highlighting targets can aid their detection. We provided soldiers with ATD that was more likely to detect one target identity than another, potentially acting as an implicit identification aid.

METHOD

Twenty-eight soldiers detected and identified simulated human targets in an immersive virtual environment with and without ATD. Task difficulty was manipulated by varying scene illumination (day, night). The ATD identification bias was also manipulated (hostile bias, no bias, and friendly bias). We used signal detection measures to treat the identification results.

RESULTS

ATD presence improved detection performance, especially under high task difficulty (night illumination). Identification sensitivity was greater for cued than uncued targets. The identification decision criterion for cued targets varied with the ATD identification bias but showed a "sluggish beta" effect.

CONCLUSION

ATD helps soldiers detect and identify targets. The effects of biased ATD on identification should be considered with respect to the operational context.

APPLICATION

Less-than-perfectly-reliable ATD is a useful detection aid for dismounted soldiers. Disclosure of known ATD identification bias to the operator may aid the identification process.

Go-stimuli proportion influences response strategy in a sustained attention to response task

The sustained attention to response task (SART) usefulness as a measure of sustained attention has been questioned. The SART may instead be a better measure of other psychological processes and could prove useful in understanding some real-world behaviours. Thirty participants completed four Go/No-Go response tasks much like the SART, with Go-stimuli proportions of .50, .65, .80 and .95. As Go-stimuli proportion increased, reaction times decreased while both commission errors and self-reported task-related thoughts increased. Performance measures were associated with task-related thoughts but not task-unrelated thoughts. Instead of faster reaction times and increased commission errors being due to absentmindedness or perceptual decoupling from the task, the results suggested participants made use of two competing response strategies, in line with a response strategy or response inhibition perspective of SART performance. Interestingly, performance measures changed in a nonlinear manner, despite the linear Go proportion increase. A threshold may exist where the prepotent motor response becomes more pronounced, leading to the disproportionate increase in response speed and commission errors. This research has implications for researchers looking to employ the SART and for more applied contexts where the consequences of response inhibition failures can be serious.