FOOD STIMULI AND GENDER

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3.5 Data Analysis
3.5.1 Areas of Interest: Defining and Position
The accuracy of the eye tracker is the average difference between gaze position and
the position recorded by the eye tracker (Holmqvist et al., 2011). For this experiment,
accuracy was verified by calibrating before each recording with the calibration card provided
by Tobii Technology. Due to the accuracy error of the eye-tracking glasses, drawing areas
of interests (AOIs) too close to the edges of the image would allow a loss of fixation and a
margin drawn too large would allow fixation counts, which are outside of the stimuli in
reality. Consequently, the accuracy of the eye tracker is important when deciding the size of
an AOI (Holmqvist et al., 2011).

Figure 8: AOI around Food Stimuli

Areas of interests (AOIs) for this experiment were defined with a margin of 0.9
degrees for all food stimuli (see Figure 7). The margin was defined based on the calibration
error admitted, with 0.9 being the mean between 0.6 and 1.2 degrees (see Chapter 3.4). Thus,
AOIs were drawn at the edges of each food without leaving any margin. Each AOI was
carefully drawn once for each food stimuli and then used for all participants via the copy
and paste function of the Tobii Pro Glasses Analyzer Software, assuring identical AOIs for
all participants.