Oculomotoric Evidence for a Speed-Accuracy Trade-off in Selective Attention Tasks during Sleep Deprivation

sleep deprivation, fatigue, eye tracking, visual search Introduction: The effects of sleep deprivation (SD) on selective attention can be studied by visual search tasks, such as conjunction (CST) and spatial configuration (SST) search. As in other task domains, SD leads to a cognitive slowing and a decrease in accuracy, but also to a deficiency in adjusting response time to an increase in the number of items in the search display. It is currently unclear what mechanism underlies the decrease in accuracy in selective attention under sleep loss. Here we used gaze tracking in visual search tasks, hypothesizing cognitive slowing to result in longer fixation durations and slower saccades. Methods: Visual search performance (response time, sensitivity d’) and associated gaze behavior were recorded in sleep deprived participants (N=24, age: 25 ± 5 STD; 12 women), kept awake during a 24 hour period, and in a control group (N=24, age: 26 ± 4 STD; 10 women) with a time-in-bed of 8 hours. Results: We were able to replicate the increase of response time under SD compared to the control group (CST: p = 0.019; SST: p < 0.001) and a decrease in sensitivity d’ (CST: p = 0.03; SST: p < 0.001).The oculomotoric measures provided indications of a cognitive slowing in slower saccade velocities for the SD group compared to the control group (CST: p < 0.001; SST: p < 0.001). In contrast, fixation durations decreased in the SD group relative to the control group (CST: p = 0.018; SST: p = 0.008). Moreover, the change in fixation duration due to sleep deprivation (i.e. difference from baseline) was positively correlated with the change in task accuracy (CST: ρ = 0.29, p = 0.048; SST: ρ = 0.33, p = 0.022). Conclusion: The oculomotoric changes under sleep deprivation suggest that tasks requiring selective attention may suffer not only due to general cognitive slowing, but also from an unfavorable speed-accuracy trade-off: decision speed per item - as derived from fixation durations - increases, while accuracy decreases in turn.