Cognitive load affects gaze dynamics during real-world tasks

In everyday tasks, active gaze is used to gather information for the actions we perform. The cognitive resources required for such gaze control have rarely been investigated. We examined how a secondary cognitive load task would affect gaze during tea- and sandwich-making, everyday tasks which involve sequences of object-related actions (Hayhoe in Vis Cogn 7(1-3):43-64, 2000 and Land et al. in Perception 28(11):1311-1328, 1999). Participants performed these tasks while wearing a mobile eye-tracker, while also counting backwards by threes (high cognitive load) or by ones (low cognitive load). Our findings revealed that participants were slower in tasks and sub-tasks and exhibited more fixations on irrelevant objects in high-load than low-load conditions. Furthermore, the eye-hand span was reduced under high-load conditions, meaning that participants were less likely to look ahead of their manual actions. These findings reveal specific effects of cognitive load in realistic, everyday situations, and begin to shed light on the mechanisms behind gaze control in active tasks. These mechanisms are not resource-free.