Henri Etel Skinner^1,2 (), Isabel Ruacho¹, Janani Aiyer¹, Barry Giesbrecht^1,2; ¹University of California Santa Barbara, ²Institute for Collaborative Biotechnologies

Vigilance is required when continuously monitoring for rarely occurring signals in the visual environment over time. When engaged in continous monitoring tasks, one robust phenomenon is a decline in detection rate as subjects continuously monitor for signals. One key parameter to this vigilance decrement may be the probability of target occurrence. We utilized the Continuous Temporal Expectancy Task (CTET) to observe performance across three different target probabilities (10%, 15%, 20%) in a within-subjects design. In this task, subjects (n=56) monitored a stream of gray-scale images appearing for brief durations (800 ms) and were instructed to respond when an image appeared for a slightly longer duration (1200 ms, targets). Furthermore, to discriminate between changes in sensitivity and response criterion, a signal detection theory approach was employed. A robust vigilance decrement, indicated by a decline in detection rate (b = -0.031, se = 0.004, p < 0.001), was observed across time. We also observed a decline in d-prime (b = -0.093, se = 0.015, p < 0.001) and an increase in criterion (b = 0.052, se = 0.008, p < 0.001) across time. There was an effect of probability on response rate, such that higher target probability yielded higher response rates (b = 36.030, se = 1.969, p < 0.001). Additionally, there was an effect of probability on d-prime, such that higher target probabilities yielded higher d-prime (b = 0.936, se = 0.409, p < 0.05). These findings together support the idea that the vigilance decrement is associated with both a decrease in sensitivity as well as an increase in criterion — suggesting attentional processes alone do not fully characterize vigilance performance. Furthermore, our results suggest the vigilance decrement is robust to modest changes in target probabilities and concurrent changes in response rate.

Acknowledgements: Research was sponsored by the U.S. Army Research Office and accomplished under cooperative agreement W911NF-19-2-0026 for the Institute for Collaborative Biotechnologies.