Conscientiousness Protects Visual Search Performance from the Impact of Fatigue
Justin Grady, George Washington University, Department of Psychological & Brain Sciences
Visual search—looking for targets among distractors—underlies many critical professions (e.g., radiology, aviation security) that demand optimal performance. As such, it is important to ameliorate negative factors such as fatigue—mental and/or physical tiredness that leads to diminished function. One way to reduce the detrimental effects is to minimize fatigue itself (e.g., scheduled breaks, adjust pre-shift behaviors), but this is
not always possible. This project explored whether some individuals are less susceptible to the impact of fatigue than others; specifically, if conscientiousness, the ability to control impulses and plan, moderates fatigue’s impact. Participants (N=374) self-reported their energy (i.e., the inverse of fatigue) and conscientiousness levels and completed a search task. Preregistered linear mixed effect analyses revealed main effects of energy level (lower energy reduces accuracy) and conscientiousness (more conscientiousness increases accuracy), and, critically, a significant interaction between energy level and conscientiousness. A follow-up analysis divided participants into above- vs. below-mean conscientiousness groups, revealing a significant negative relationship between energy level and accuracy for the below-mean, but not above-mean, group. The results raise intriguing operational possibilities for visual search professions, with the most direct implication being the incorporation of conscientiousness measures to personnel selection processes.
Visual search, looking for targets among distractors, is an important skill involving an array of underlying cognitive mechanisms, including perception, memory, attention, and decision making (Eckstein, 2011; Nakayama & Martini, 2011). Visual search underlies many professional tasks that can have life-or-death outcomes, including aviation security (e.g., Mitroff et al., 2018; Wetter, 2013), medical image perception (e.g., Horowitz, 2017; Krupinski, 2015; Van der Gijp et al., 2017), lifeguarding (e.g., Lanagan-Leitzel et al., 2015), and many military operations (e.g., Nelson et al., 2015). In such professions, human operators conduct what can be complicated tasks that demand high levels of attention, vigilance, and engagement (Krupinski, 2015; Wetters, 2013), and unfortunately, the operators can be susceptible to fatigue—a state of tiredness and diminished functioning.
Extensive research has explored the detrimental impact of fatigue on cognitive performance and occupational safety, suggesting that fatigue arises from an array of conditions, including long work hours, unusual shift times, and stressful employment settings, which are all common to professions involving visual search (e.g., Williamson & Friswell, 2013). Fatigue is broadly considered to be a complex multidimensional symptom in which individuals experience physical tiredness and a lack of energy (Schwid et al, 2003). Accordingly, fatigue has an array of implications for a range of cognitive and motor tasks, and produces known deficits in areas such as sports performance (Smith et al., 2016), driving (Lal & Craig, 2001), and military operations (Miller et al., 2018).
For visual search, detriments from fatigue are generally thought to stem from both a prolonged time spent on a task and the searchers’ mental and/or physical state when starting the task (Bailey et al., 2007). While both factors are important, the current study focused on participants’ mental and/or physical state when they began a testing session (i.e., “fitness-for-duty”). In professional visual search environments, each operator arrives at work in their own particular state of readiness, which can vary between and within individuals from one day to the next. The current study focused on one particular factor of individual differences that might moderate the impact of fatigue on visual search performance: Conscientiousness—the ability to control impulses, be goal directed, plan, and delay gratification (Roberts et al., 2009). Conscientiousness is a strong candidate trait as previous work has shown that more conscientious individuals are better searchers (Biggs et al., 2017; Spain et al., 2017). Moreover, conscientiousness may facilitate core cognitive abilities that underlie visual search performance. For example, it has been suggested that more conscientious individuals place a higher degree of emphasis on success and rule learning compared to less conscientious individuals, leading to higher accuracy on working memory tasks (Studer-Luethi et al., 2012) and superior performance on cognitive shifting tasks (Fleming et al., 2016). As such, the goal of the current study was to explore if conscientiousness moderates the relationship between fatigue and visual search performance.
The study design and analyses were preregistered (https://osf.io/7w8dm). Participants (N=374) completed a large set of self-report surveys via Qualtrics, but only two were assessed for the current study. First, participants completed a “readiness survey” that asked about typical and recent sleeping habits, caffeine use, and other related factors. One question asked participants to rate their energy level with lower energy level ratings corresponding to higher fatigue and vice versa. A measure of fatigue level was calculated for visualization purposes in by subtracting the participants’ subjective energy rating (on a 0-100 scale) from 100. The second measure of interest was the conscientiousness subscale from the Big-5 Personality Inventory (John & Srivastava, 1999). This subscale, which is calculated as the average response on a 1 to 5 scale for 9 questions, was used to measure participants’ self-reported level of conscientiousness. No other survey data, including other subscales from the Big-5 Inventory, were analyzed as part of this project as laid out in the preregistered analysis plans.
The visual search performance measures came from Airport Scanner (Kedlin Co.)—a mobile game wherein players search for prohibited items in simulated bags at a virtual airport security checkpoint. Airport Scanner was a publicly-available game and the developers made the data available for research purposes (e.g., Ericson et al., 2017; Kramer et al., in press; Mitroff et al., 2015). All behavioral data for the current study came from the Big Plane Challenge in the R&D Lab level of the game; the Big Plane Challenge task was fully described in Mitroff et al. (2018). After completing two tutorial levels that provided practice and introduced the game dynamics, players completed 72 trials of gameplay. A trial was defined as a single bag that moved laterally across the screen. If participants detected a prohibited item (i.e., target), they were instructed to tap on the screen at the location of the item.
Linear mixed effect (LME) models were used to assess target-present accuracy and target-present response time as dependent variables with energy level, conscientiousness, and their interaction as the fixed effects of interest. Gender (male, female, no response) and participant cohort (in-lab, virtual) were assessed as categorical random effects of no interest. The LME models were defined as: accuracy [or response time] ~ 1 + energy level + conscientiousness + energy level*conscientiousness + (1|gender) + (1|cohort). The interaction effect of energy level and conscientiousness for each model was of primary interest, given the hypothesis that the effect of fatigue on visual search performance would be moderated by conscientiousness.
The average energy level rating was 62.56 (SD=19.29, range=10 to 100), and the average conscientiousness score was 3.55 (SD=0.58, range=2.22 to 5). The average visual search target-present accuracy was 71.56% (SD=14.13%, range=21.05% to 97.37%), and the average visual search target-present response time was 2713.56ms (SD=502.99ms, range=1574.74ms to 4459.63ms).
The LME model for target-present accuracy produced a significant main effect of the energy level (F(1, 370)=5.071; p=0.025) such that higher levels of fatigue related to lower accuracy (i.e., fatigue was negatively correlated with accuracy), and a main effect of conscientiousness (F(1, 370)=4.516; p=0.034) such that higher levels of conscientiousness related to higher accuracy (i.e., conscientiousness was positively correlated with accuracy). Most critical for the current project, the model produced, and a significant interaction between fatigue and conscientiousness on visual search accuracy (F(1, 370)=4.117; p=0.043). The LME model for target-present response time produced no significant main effects (energy level: F(1, 370)=2.312; p=0.129; conscientiousness: F(1, 370)=2.486; p=0.116), nor a significant interaction (F(1, 370)=1.993; p=0.159).
Given the significant interaction between energy level and conscientiousness in the LME model of accuracy, follow up analyses were conducted to delineate the nature of this relationship. The participants were divided into above-mean and below-mean conscientiousness groups based on a mean split of the conscientiousness scores, and separate correlation analyses of visual search accuracy as a function of fatigue were conducted for each group. The split was done with the mean, instead of the median, since 22 participants fell at the median value for conscientiousness. The above-mean conscientiousness group had an average conscientiousness score of 4.08 (SD=0.34), and there was not a significant correlation between fatigue and accuracy (N=191, r=0.034, p=0.644). The below-mean conscientiousness group had an average conscientiousness score of 3.05 (SD=0.33), and there was a significant correlation between fatigue and accuracy (N=183, r=-0.176, p=0.017), with higher fatigue corresponding to lower visual search accuracy. The two correlations significantly differed from one another; z=2.03, p=0.042.
The current study used an individual differences approach to explore the relationship between fatigue and visual search performance. Fatigue negatively affects search (Bailey et al., 2007; De Gennaro et al., 2001; Santhi et al., 2007), which has profound implications for a wide swath of professions, including aviation security, radiology, lifeguarding, and more. Given that a mistake in such professions could have life-or-death consequences, it is important to know which factors may help to combat fatigue-induced performance decrements.
This study first contributed to the extant literature by providing supporting data that fatigue negatively related to visual search accuracy. Second, there was also a significant main effect of conscientiousness (higher levels of conscientiousness related to higher visual search accuracy), which supports prior results (Biggs et al., 2017; Spain et al., 2017). Finally, the primary question and novel finding of the current study was that the impact of
fatigue on search accuracy was moderated by conscientiousness. Individuals who self-reported higher levels of conscientiousness did not demonstrate a significant effect of fatigue on accuracy while those who self reported lower levels of conscientiousness did have a significant relationship between fatigue and accuracy, with higher fatigue relating to lower accuracy. The current findings have the potential to inform professional operations that rely on visual search. For example, knowing that more conscientious individuals are less susceptible to the negative impacts of fatigue could inform hiring and staffing decisions for aviation security, military operations, lifeguarding, and more. A fair question, though, is just how operationally meaningful is this particular effect; is the impact of the fatigue conscientiousness relationship relevant for visual search professions, and should they consider incorporating this knowledge into their operational plans? Prior work using the same experimental paradigm provides insight to this issue. Specifically, in a prior study (Mitroff et al., 2018), US airport screening officers completed a visual search task that was nearly identical to the one used in the current study (the professional security screeners completed a commercial version of the level of the publicly available game that was used in the current study). Critically, the officers’ performance in that task significantly correlated with their on-job performance such that those who were better at the visual search task were both more accurate and quicker at actual checkpoints. This suggests that this paradigm is sensitive to operational outcomes, and the current results demonstrate that this paradigm is also sensitive to the impacts of fatigue and conscientiousness. As such, it is reasonable to suggest that these data offer a potentially generalizable outcome with practical implications. Note that the participants who self-reported lower levels of conscientiousness varied in visual search accuracy by approximately 5% based upon their level of fatigue. A 5% shift in accuracy could manifest in a massive operational impact for aviation security given the sheer number of searches conducted each day across airports around the world and the implications of even a single missed target.
Visual search, finding targets among distractors, underlies many critical professions, including aviation security, medical imaging, and various military operations. Operators must perform optimally so it is important to know what factors influence performance; prior research has demonstrated that fatigue—mental and/or physical tiredness and diminished function—is one such detrimental factor. The current study focused on pre-task readiness/energy level, which is a particularly thorny form of fatigue given it cannot easily be addressed by modifying on-job operations. An individual differences approach demonstrated that some people were less susceptible to the detrimental effects of this form of fatigue than other people; specifically, the negative impacts of fatigue were moderated by conscientiousness—the ability to control impulses and plan. The results have broad implications, including for hiring practices in occupations that rely on visual search.