In this section, we will provide information about what types of research can benefit from the combination of eye tracking and galvanic skin response (GSR) data.
Eye tracking can provide unique insights into cognitive processes and visual attention. There are, however, other aspects of experience and perception that are more elusive to capture in gaze behavior, like the emotional or mental state. Adding GSR to eye tracking can provide more dimensions of information and help understand the reasons underlying visual performance.
GSR has been closely linked to the emotional state and arousal level of a participant, and has been used as a sensitive index of non-conscious emotional intensity and cognitive processing. Some fields of research where GSR has been widely applied include emotion (e.g., fear, threat, happiness), decision making, clinical research (e.g., post-traumatic stress disorders, depression, autism), usability and marketing research (e.g., product and media content evaluation).
There are other biometric techniques that can also give insights about similar emotional processes that are measured with GSR, such as EEG or heart rate variability (HRV). The main advantages of GSR over other biometric techniques are the easy setup, the inexpensiveness of the sensors and the easy visual interpretation of the signal. The main limitation of the GSR technique is the rather slow GSR response time, which usually influences the experimental design with longer stimulus exposure times and inter-stimulus intervals (ISI).
When we are interested in the general emotional level of our participants over a period of time, GSR can be added to an eye tracking study without any significant change in the study design. For example, in TV media research, adding GSR to our eye tracking study will provide emotional information to help understand what moments of the TV content are more emotionally engaging for the participants. Also, in any eye tracking study where the participants’ arousal level is expected to change over time, GSR can be added to the experiment as a measure of the workload or stress level. Web usability studies, or decision making research are examples where the stress level can give additional information to the main measure of visual attention.
Eye tracking and GSR has also been used when we are interested in measuring the emotional reaction and eye movements associated to specific stimuli. Some examples of research can be found in the area of emotion regulation. Wieser et al., (2009) studied the emotional reaction and gaze behaviour that faces with direct and advert gazes produced in low, medium and high socially anxious participants. Also, the combination of eye tracking and GSR has been used in fear research with healthy and clinical populations. Wiemer et al., (2013) used an inattentional blindness paradigm to study the emotional reaction and gaze behaviour of an unexpected spider.
Finally, GSR and pupil dilation have been both linked to similar mechanisms of sympathetic activity. Some studies have studied this link using eye tracking and GSR to understand better the physiological mechanisms and to get further insights about the arousal level or cognitive load of a participant during a certain task.
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