Blink rate has been suggested to be a proxy for cognitive load. However, there are mixed results regarding this association, which is modulated by the visual demand of a task or when a dual-task paradigm is performed. This study investigated blink rate as a measure of cognitive load using a dual task paradigm (i.e., primary task = flying an aircraft; secondary task = auditory oddball task) to specifically assess changes in cognitive load across two flight phases (i.e., cruise, landing). Primary task performance suggested participants focused on maintaining aircraft control across task conditions, but a significant dual-task difference score in auditory oddball task performance (p<0.001) was still evident across flight phases. Blink rate did not show similar differences across flight phases. Our results demonstrate that the utility in using blink rate to measure cognitive load may be limited in its application to more complex naturalistic scenarios when using an auditory dual-task.

Invisible fiducial markers are introduced for localization of Areas Of Interest (AOIs) in mobile eye tracking applications. Fiducial markers are made invisible through the use of film passing Infra-Red (IR) light while blocking the visible spectrum. An IR light source is used to illuminate the markers which are then detected by an IR-sensitive camera, but which are imperceptible by the human eye. We provide the first empirical study that demonstrates such invisible markers are not distracting to a given task, as demonstrated in a flight simulator where distraction of visible and invisible markers are compared between experienced and novice pilots. Fixation frequency and subjective distraction scores showed that visible markers disrupted natural gaze behaviour, particularly in novice pilots. Our findings show that invisible markers should be used when there is a need for them to remain inconspicuous.

Invisible fiducial markers are introduced for localization of Areas Of Interest (AOIs) in mobile eye tracking applications. Fiducial markers are made invisible through the use of film passing Infra-Red (IR) light while blocking the visible spectrum. An IR light source is used to illuminate the markers which are then detected by an IR-sensitive camera, but which are imperceptible by the human eye. We provide the first empirical study that demonstrates such invisible markers are not distracting to a given task, as demonstrated in a flight simulator where distraction of visible and invisible markers are compared between experienced and novice pilots. Fixation frequency and subjective distraction scores showed that visible markers disrupted natural gaze behaviour, particularly in novice pilots. Our findings show that invisible markers should be used when there is a need for them to remain inconspicuous.