Work, aging, mental fatigue, and Eye movement dynamics

Computer work, as a prevalent occupation, involves different levels of mental load and fatigue with possible negative health effects. The population aging has also led to increased elderly workers highlighting the need for protective measures.Mental load and fatigue are multidimensional psychophysiological phenomena. Inefficient work routines accelerate fatigue development, associated with declined cognitive resources and increased errors. Micro-breaks are strategic solutions to counteract fatigue subject to design constraints, e.g. timing plan. Eye tracking is a promising technology for the quantification of mental load and fatigue levels. The oculometrics were aimed to be studied in association with age, mental load and fatigue, allowing early detection of fatigue, and thereby applying biologically-valid micro-breaks to decelerate fatigue development.Upon this, three Studies (I-III) involving 58 young and elderly individuals were conducted. A task, resembling computer work, was developed to induce mental load. Gaze positions and pupillary responses were recorded during the task execution to detect ocular events (saccades, fixations, and blinks), and thereby computing oculometrics e.g. fixation duration. In Study I, the task was performed on three load levels in a counterbalanced order across two days. Between-day reliability and mental-load sensitivity of 19 oculometrics were assessed, besides measuring performance and perceived workload. In Study II, fatigue development was explored in oculometrics during 40-min performance of the task while subjective fatigue and performance metrics were obtained. A predictive model of fatigue was developed in Study III based on the ocular data collected in Study II. An oculometrics-based biofeedback system was implemented in real time to detect fatigue using the developed model, which triggered micro-breaks upon fatigue detections to counteract it during the task. The optimality of the system was compared with self-triggering micro-breaks in terms of fatigue trends and workload.A group of oculometrics was sensitive and reliable to reflect mental load and fatigue in the young and elderly individuals. Similar trends in the oculometrics were observed with increased mental load and fatigue levels, implying shared neural systems for both conditions. Although age-related differences were exhibited in some oculometrics, age did not directly contribute to the predictive model of fatigue. The oculometrics-based biofeedback provided an improved solution for timing plan of micro-breaks in reducing workload and fatigue development compared with self-triggering micro-breaks. The oculometrics-biofeedback system made a benchmark towards productive and healthy computer work.