Looking Beyond Looking Time: A Systematic Review of Eye-Tracking Measures of Social Attention in ASD

Background:

Eye-tracking technology has been a powerful tool for investigating social attention in ASD (Guillon et al., 2014). The majority of measurements of social attention have relied solely on looking time measures, interpreting longer looking times as an indication of preference for a certain area of interest (AOI). Based on this measurement it has been shown that social attention is reduced in individuals with ASD as compared to typically developing controls, ASD individuals directing less of their visual attention to social stimuli than typically developing controls (for a meta-analysis see Chita-Tegmark, 2016). However, there are many questions regarding social attention that cannot be answered through looking time measures, such as: do individuals with ASD prioritize social attention in the same way and to the same degree as typically developing controls? Do individuals with ASD explore the visual social world to the same extent? Do individuals with ASD maintain the same kind of focus on social stimuli as typically developing controls? Fortunately, eye-tracking technology makes possible a large number of different kinds of measures that can be used to tackle a variety of questions related to social attention in ASD.

Objectives:

The objective of this research is to systematically examine the eye-tracking literature in order to create an inventory of the available eye-tracking measures and to synthesize the findings they have enabled pertinent to social attention in ASD.

Methods:

A thorough search of the PubMed database was performed using the Boolean phrase ((ASD) OR (autism) OR (Asperger)) AND ((eye-tracking) OR (eye tracking) OR (eye gaze)). Articles meeting the following criteria were selected: 1) the article was an empirical study 2) the study compared individuals with ASD with TD controls 3) the study used eye-tracking technology 4) the study involved social stimuli 5) the study had a free viewing task and 6) the study included a measure in addition to and/or other than looking time. All eye-tracking measures of social attention were catalogued and the results obtained by means of these measures were synthesized.

Results:

The measures fell into three major categories: measures of prioritization of social attention (including: location of first fixation, latency to first fixation and progression of exploration over time), measures of persistence of social attention (including: average fixation time, characteristics of first fixation and visual perseverance) and measures of exploration of social information (including: saccade length, saccade paths characteristics, number of saccades and spread of fixation). A preliminary synthesis of findings suggest differences between individuals with ASD and typically developing controls for each of these major features of social attention, with less prioritization of social information, less persistence of social attention and less exploration of social information.

Conclusions:

By harnessing the full potential of eye-tracking technology and research in terms of available measures it is possible to gain a more nuanced understanding of social attention in ASD.