The goal of the following protocol is to provide methodological recommendations that optimize research, design, data acquisition, and psychometric analysis for eye tracking young children with autism spectrum disorders or other developmental disabilities. This is achieved by first selecting appropriate eye tracking equipment and creating a suitable testing environment that mitigates the complications that accompany eye tracking young children with autism. As a second step, positioning the child for optimal eye tracking while maintaining his or her interest and compliance are crucial for obtaining high quality data.
Next, eye tracking data is analyzed in order to characterize metrics of fixation patterns, or examine oculomotor properties. Results can show whether children with and without autism spectrum disorders differ in their visual attention patterns. A determination that is typically based on fixation analysis to areas of interest or inspection of saka dynamics.
Generally, individuals new to this method often struggle as eye tracking young children with autism involves unique challenges that are not present when eye tracking typically developing older children or adult populations. When testing young children with autism spectrum disorders, it is best to select an eye tracking system that accounts for head motion, but that does not restrict the head or require minimal head movement. Systems with a sampling rate of at least 50 hertz are adequate to examine scanning patterns.
But a higher sampling rate of at least 250 hertz is recommended for investigating subtle ocular-motor behavior. Sparse room decor is recommended in order to minimize distraction. Similarly, a dimly lit room helps enhance the salience of the display, but avoid testing in a completely darkened room.
As young children with a SD may experience, visual and or auditory hypersensitivities completely darkened environments may also increase pupil dilation, which can make the pupil more difficult to track, to further reduce the chances of distraction. Ensure the experimenter is not visible during the experiment by placing a partition between the eye tracking station and the experimenter computer, or simply position the experimenter out of view from the participant. If possible, it is best to allow the participating child to gain familiarity with the testing space and experimenter prior to testing in order to reduce apprehension to the novel environment.
At the very least, an apprehensive child should be accompanied by a parent or familiar adult throughout the testing session. Now, position the child for acquiring eye tracking data while some children do well sitting alone in a car seat, many others only remain compliant while sitting upon the lap of the caregiver who should sit in an office chair that can easily be raised or lowered. Play a video or cartoon on the display monitor to help the child feel at ease while ensuring attention is directed towards the display.
Take advantage of the child attending to the screen to adjust both the height of the chair based upon the child's stature and the distance from the display so that he or she can be positioned with an optimal eye tracking range. The line of sight and visual angle should be standardized across all participants at this point. Instruct caregivers to close their eyes and refrain from communicating with their child during testing to avoid influencing the results.
For software that displays the participant's eyes within a range of acceptable head motion, make sure the eyes appear in the middle of this window. This increases the chances that the eye tracker will retain an image of the eye even if the child slouches straightens or sways during testing. Once properly positioned, begin the calibration procedure.
Children with a SD may be unwilling or unable to follow verbal instructions, so use dynamic stimuli accompanied by sound to capture the child's attention to each calibration point. Typically, a five point sequence is brief enough to retain the child's attention while also providing an accurate calibration. Though a two point calibration is sometimes used with infants to maximize the child's visual attention during testing, use compelling stimuli in a concise task that has minimal task demands, such as a passive viewing task, including an inter stimulus.
Animation with an accompanying sound effect can help to redirect attention to the display for children whose attention has lapsed. Additionally, positioning this inter stimulus animation in a predefined location can ensure that all visual scanning patterns begin in the same spot for all participants in the task shown here. This is done so that gaze is not biased to the person or object prior to the start of the trial.
For lengthy tasks, use the interra stimulus animation as an anchor to determine if calibration drift is occurring. Typically, if drift exceeds three degrees of visual angle as shown here, recalibration should be administered if multiple tasks are included. Recalibration is recommended between each to eliminate drift over the course of testing.
Most eye tracking systems yield raw data files that include a timestamp X and Y coordinates of the point of regard the distance from the OR stimulus, along with an index that characterizes an event or change in stimulus presentation to control for missing gaze data conduct analysis as a proportion of gaze time on screen instead of in absolute values. To analyze fixation patterns as seen here, temporal and spatial components are required. A fixation is often defined as the point of regard remaining within a diameter of one degree of visual angle for at least 100 milliseconds.
Common dependent variables in fixation analysis include number of fixations, average duration of fixation, total fixation time, and the spatial arrangement or sequence of individual fixations fixation analyses are often conducted within predefined areas of interest or AOIs. Children with and without a SD may differ in their fixation time to specific AOIs such as the eyes on a face, their latency to first fixate AOIs or in the patterns of their gaze shifts between AOIs. Characterizing the velocity of eye movements allows for the examination of other properties of oulu motor dynamics, including the distribution or pattern of SEC velocities, the distribution or pattern of SEC amplitude, the distribution or pattern of SEC duration, as well as the latency of SEC and accuracy of SEC termination.
Displayed here is a representative fixation map. The circles indicate individual fixations by a single child with a SD while viewing a static image Fixations from this and similar tasks are analyzed across participants to determine if children with and with a SD differ in their visual attention to various AOIs. This figure demonstrates that within a visual exploration paradigm, children with a SD fixate on fewer social images than typically developing or TD children.
When high autism interest HAI objects are concurrently displayed. When low autism interest LAI objects are presented with social stimuli, however, exploration of social images does not differ significantly between groups suggesting that social attention in a ST is modulated based on the relative salience of competing stimuli. After watching this video, you should have a good understanding of how to more effectively eye track young children with autism by selecting appropriate equipment and creating a suitable testing environment by properly positioning the child and maintaining his attention to ensure that quality eye tracking data is obtained, and by analyzing metrics relevant to your research question, you'll be well equipped to conduct eye tracking studies with young children on the autism spectrum.
