Are the eyes windows to our minds?
Applications of eye tracking in psychology
The range of technologies applied to study the brain and behavior has evolved drastically in the past two decades. Almost any journal in the field of experimental psychology will feature articles that use one of these keywords: EEG, MEG, TMS, fMRI, PET. This is not to say that self-report questionnaires and behavioral testing are no longer relevant or important, but the aforementioned technologies often provide the benefit of more reliable and valid results when it comes to measuring unconscious or automatic processes. Furthermore, from a visualization and analytics perspective, psychological research has developed and grown immensely due to the technological boom. A recent technology that is gaining attention is eye tracking — though many researchers only have a vague idea of the tool.
Psychophysicists, namely Alfred L. Yarbus, began studying saccadic eye movements in the 1960s. Since then, research has linked the eyes to numerous cognitive processes, emotion perception, developmental psychopathology, and language processing, as well as user/consumer behavior and marketing strategy. In brief, an instrument records eye positions and movements, providing insight into autonomic processing of visual information for clinical and experimental applications, by tracking light reflected from the cornea. Modern eye tracking technology, such as SensoMotoric Instruments (SMI) Gaze and Eye Tracking Systems, enable precise recording and replaying of subjects’ eye positions and movements, while programs, such as SMI BeGaze, eliminate outliers, locate areas of interest (AOIs), and clean-up the raw data.
It is imperative that researchers possess a comprehensive understanding of how to use the tools and software programs that are supposed to test the desired construct(s) in their experimental paradigm. This is especially true when it comes to eye tracking studies, because the data output is immense. Conceptualize the totals and averages of the number, length, and duration of all fixations and saccades, as well as variations in pupil diameter and pupil size! Data analysis becomes overwhelming as the complexity of visual stimuli, number of variables, and length of experiment increase. For experimental validity and practical reasons, researchers are advised to code and randomize the visual stimuli sensibly, test stimuli selection in a validation study, and limit the time duration and difficulty of experimental task as much as possible. More specifically, it will help to pilot the experiment in several settings with various lighting and set-ups, periodically calibrate subjects’ eyes to improve the accuracy of the gaze coordinates computed by the tracker, and examine the significance of effects within- and between- subjects.
In combination with other conventional research tools, eye tracking data is extremely helpful in diagnosing and understanding diseases, for example, Attention Deficit Hyperactivity Disorder, Autism Spectrum Disorder, Schizophrenia, Parkinson’s disease and Alzheimer’s disease. This is not a complete guide to eye tracking studies. Simply, researchers must be aware and patient. Eye tracking technology — if applied correctly — creates a bridge between behaviorism and cognitivism and shines light into a myriad of disciplines.
