Consistent with previous eye tracking results, individuals in the typically developing group spent a greater percentage of time than those in the ASD group looking at the eyes, regardless of whether the face was familiar or unfamiliar. These results replicate clinical and research reports of reduced attention to eyes among individuals with ASD. Because this pattern of atypical attention to the eyes was consistent regardless of whether the faces were familiar or unfamiliar, this pattern appears to be general and not affected by familiarity of the face.
A novel result of the present study was the finding that, in contrast to typical individuals, individuals with ASD did not exhibit differential gaze patterns when viewing Familiar versus Unfamiliar faces. Specifically, it was found that typical individuals made significantly more frequent fixations when looking at the Unfamiliar faces versus the Familiar face, whereas the frequency of gaze fixations was not influenced by familiarity for the individuals with ASD. Interestingly, both groups made a similar number of fixations and spent about the same amount of time looking at the highly Familiar and New Friend faces. This suggests that within the context oft this experiment, repeated exposure to a face (the New Friend) led to patterns of attention that were similar to that of the highly Familiar face. The social relevance of the face, therefore, did not appear to have an impact on patterns of attention for either group.
Examination of facial regions revealed that both groups made a significantly greater percentage of fixations and spent a larger percentage of time on the eyes than the mouth for all face categories. This was true for the ASD group despite overall reduced attention to the eye region compared to the typical group, and is in contrast to previous studies that found that individuals with ASD spend more time looking at the mouth than the eyes (Klin et al. 2002
; Spezio et al. 2007a
). This difference in findings across studies likely reflects the differences in face stimuli used. In Klin et al. (2002)
, participants viewed dynamic images of movie characters interacting and talking with each other; participants in Spezio et al. (2007a)
viewed images of emotional faces. In both of these experiments, the task may have emphasized how faces are “used” to provide social and emotional information. This may have resulted in a reliance on the mouth region to gain verbal and expressive information. In the current experiment, the participants were presented with static pictures of faces exhibiting neutral expressions similar to those most used in fMRI and ERP (event-related potential) experiments. The participants were not required to interpret the stimuli or make judgments regarding the faces. Given the opportunity to view the face in any way they wished (per the instructions provided to them), participants in both groups spent more time looking at the eyes than the mouth.
Individuals in the typical and ASD groups made a greater percentage of fixations and spent a larger percentage of time on the eye and mouth regions of the Unfamiliar faces than the Familiar face, with similar fixation patterns for the Familiar and New Friend stimuli. One possible explanation for this pattern of results is that the less familiarity a person has with a face, the more time they spend examining its integral features, particularly the eyes and mouth. With increased familiarity and exposure, one may gain efficiency or need less time to investigate the central features of the face. Given that individuals with ASD did not spend more time on the central features of the Familiar versus Unfamiliar face, the current results call into question the hypothesis that there is a link between fusiform gyrus activation and fixation patterns.
A facial recognition task was included to examine whether facial recognition accuracy differed depending on familiarity with a face. Of note, this task was relatively easy in comparison to standardized tests such as the Wechsler Memory Scale face memory test (WMS-III; 1997b
), which utilizes memory for 24 new faces. In general, the ASD group in the current study took longer than the typical group to decide whether they had previously seen the face presented to them. However, accuracy between groups did not differ.
There are limitations to the current study. While eye tracking technology is informative in terms of elucidating strategies used when viewing faces, static black-and-white images are not equivalent to real-life situations in which faces are interactive. In interpersonal situations, individuals are expected to interpret and integrate nonverbal information such as facial expressions and speech, and respond in a timely, reciprocal, and appropriate manner. This is particularly challenging given the complexity of subtle but meaningful alterations in eye gaze, emotional expression, and tone of voice that may fluctuate concurrently. Images in the current study, presented on a computer screen, lack this dynamic quality of human faces. One study has in fact demonstrated that individuals with ASD utilize different gaze patterns than their typical peers when viewing dynamic but not static social stimuli (Speer et al. 2007
). Despite this limitation, individuals with ASD still spent significantly less time focusing on the eye region compared to the typical group in the current study.
Eye tracking provides objective, non-invasive, quantitative assessment of attention to faces in general and eyes in particular, an impairment in ASD previously documented through behavioral observation. In the current study, evaluation of eye gaze patterns informs understanding of the social nuances in ASD, specifically in terms of attention to familiar and unfamiliar faces. Results from the current study suggest that repeated exposure to a face, regardless of its social relevance, leads to patterns of eye gaze that resemble those used when looking at a familiar face. This suggests repeated contact with an unfamiliar face, in and of itself, facilitates development of familiarity, an important step in forming social relationships. More ecologically valid paradigms (e.g., naturalistic social encounters) are warranted to further explore the clinical implications of such findings, including how increased exposure to faces impacts other aspects of social interactions, such as nonverbal communication, conversation, and emotional reciprocity. It may be possible that providing individuals with ASD exposure to less complex social stimuli (e.g., still images) prior to more complex interactions, helps to support social processing. The utility of eye tracking is also relevant in light of new intervention techniques designed to improve face processing abilities and strategies in individuals with ASD through the use of computerized face training (e.g., Faja et al. 2008
). Face training in autism has the potential to improve social interactions and relatedness; eye tracking allows for evaluation of strategies used and changes in gaze patterns as a function of intervention. Eye tracking may also capture individual differences in gaze patterns so that more targeted training can be provided.
In conclusion, individuals with ASD showed atypical attention to the face stimuli regardless of whether it was unfamiliar, highly familiar, or newly familiar. Their pattern of attention was characterized by less time focused on the eyes compared to typical individuals. Additionally, in contrast to the typical individuals, participants with ASD did not exhibit differential gaze patterns when viewing the highly familiar versus unfamiliar faces. These results suggest that differences in patterns of attention may not underlie the differential neural activation patterns observed when individuals with ASD view highly familiar versus unfamiliar faces.