Sleep loss and high task demand lead to fast and sloppy decision-making: eye-tracking evidence from a visual search task

Long-distance human space travel will lead to communication delays and with increasing distance from earth, support from ground control will be partially replaced by the interaction with automated support systems. To make good and fast decisions, operators need to attend to displays and quickly identify relevant among irrelevant information. We used a visual search paradigm to operationalize such tasks and studied performance under sleep deprivation. Sleep quality and quantity suffer during space missions and prior work has suggested that performance in these tasks becomes «fast and sloppy» with sleep loss. We used eye-tracking to get insight into the underlying processes that lead to this type of poor decision-making. We studied 50 healthy participants, randomized to a 24-h acute sleep deprivation group and a control group, completing a visual search task in which they had to decide on the presence/absence of a single target within sets of 10, 20, 30 or 40 search items. Eye-tracking revealed that, across both groups, visual sensitivity correlated positively with total fixation duration (TFD) and with TFD slope, i.e. the rate at which TFD increases as a function of set size. After sleep loss, sensitivity deteriorated more in trials with 30 and 40 items than in trials with 10 and 20 items, whereas TFD increased for the small, but not for the large set sizes. Thus, sleep deprivation resulted in a flatter TFD slope, which was associated with poorer performance. Against a background of general cognitive slowing (longer TFD), sleep loss impedes the allocation of sufficient search time to complete more challenging searches with larger set sizes (shallower TFD slope). This unfavorable speed-accuracy trade-off might indicate attempts to counteract the effect of sleep loss in simple tasks, which fall short due to compromised effort allocation for more demanding tasks. In consequence, decision quality of operators is most impaired when two stressors meet: high cognitive load and acute sleep loss. Eye-tracking measures are sensitive to sleep deprivation and might reflect impairment or compensatory behavior during critical operations. In scenarios of increased crew autonomy, these unobtrusive measurements could inform about operator state and help predict and prevent performance impairment due to stressors