As we go about our daily lives, our eyes are continually moving around, sampling the information that is available in the visual environment. For instance, if we want to know how somebody is feeling, we will fixate in turn on the different features of their face. When reading a story, our eyes will move from word to word, lingering on words that are more difficult to read, and backtracking when we realise that something does not make sense. When we hear somebody talking, our eyes also tend to be drawn to objects in the visual scene that we expect the speaker to mention next. By monitoring people’s eye-movements, it is possible to gain important insights into the underlying cognitive processes involved in completing these tasks. Eye-tracking also provides a critical objective measure of someone’s focus of visual attention during a particular task.
The Department of Cognitive Science operates eight eye-tracking systems housed in our behavioural and neuroimaging facilities (including the KIT-Macquarie MEG Brain Imaging Lab and the ERP Facility) at the Australian Hearing Hub and the MRI Macquarie Medical Imaging facility at the Macquarie University Hospital. We have three main eye-tracking systems available at these different sites. Each of these systems has different strengths, enabling a wide-range of applications.
EyeLink 1000 remote eye-trackers
The EyeLink remote eye-tracking systems incorporate a small camera and infra-red illuminator mounted on the desktop in front of the display screen. Participants wear a small circular sticker on their forehead, which enables the system to track their head position as they move around freely (around 20cm in any direction). This makes the system particularly suitable for testing children and other special populations. The remote system operates at 500Hz, but can record at 1000Hz and with higher spatial resolution if the participant's head is stabilized using a chin-rest. Each remote system is by default setup for use with a chin-rest.
EyeLink II head-mounted eye-tracker
The system uses three cameras: two high speed cameras allow for binocular (or dominant-eye monocular) recording of eye-movements; the third camera tracks four infrared markers mounted on the display screen, allowing the EyeLink software to automatically compensate for small head movements by tracking the position of the subject's head in relation to these markers on the screen. This means that a chin rest, or head restraint, is not required. Pupil measurements are recorded at a rate of 500 Hz (one sample every 2 milliseconds). The head-mounted tracker is currently the only system in this department that enables binocular recording. It is particularly suitable for research that involves interaction with a touch-screen.
EyeLink 1000 tower-mounted system
The tower-mounted EyeLink 1000 system provides the greatest spatial and temporal resolution. To achieve this, the participant's head must be stabilized on a chin-rest. The camera is positioned above the chinrest and monitors their eye-movements via a mirror placed between the participant and the computer screen. The mirror reflects infrared light whilst allowing visible light to pass through. This means the participant’s view of the computer screen is not affected. Our tower-mounted eye-tracker is integrated with a Curry EEG system which is housed in our ERP Facility. These integrated systems allow for brain responses to be time-locked to fixations on particular areas of interest on the screen. It also enables the simultaneous recording of eye-movements during traditional event-related potential studies.
For enquries about these facilities please contact the Eye Tracking Committee