Reading and understanding emotion is a skill most people begin to develop during infancy, such that by adulthood they are better equipped to deal with social interactions. However individuals with autism are often found to struggle with processing emotions expressed by others, though familiarity is suggested to help mitigate this. In a recent study in the Journal of Neurodevelopmental Disorders, Heather Nuske, Giacomo Vivanti and Cheryl Dissanayake from La Trobe University, Australia, set about measuring the effect of familiarity on emotion processing in autism. Utilising eye-tracking pupillometry they investigate how autistic children respond to expressions of fear in familiar versus unfamiliar people. Here Nuske explains what their findings suggest about the neurological basis of autism, and how this may aid clinical assessment and management.
What got you interested in studying emotion processing in individuals with autism?
This topic has captured my interests for many reasons, personal and professional. On the personal side, my younger brother has autism. He has taught me many things, including that each person has a unique way to perceive the world around them, and that this should be celebrated. This led me to want to study psychology and after having some great mentors along the way (including Thomas Matyas and Cheryl Dissanayake), I got interested in research and naturally gravitated towards autism research.
But why emotion research? Well this was sparked from reading inspirational work from key scholars in this and related fields (Antonio Damasio, Peter Hobson, Colwyn Trevarthen, Daniel Stern, Michael Tomasello and Mark Johnson, to name a few), and a general realisation that emotions and emotional balance underlies what every person wants from life, to be happy.
Also, my work as a therapist for children and adolescents with autism has taught me the power that non-verbal cues to emotion have in communicating ideas between people, and the difficulty that stems from not being able to effectively use this mode of communication. The transfer of emotion between people is crucial as it is the gateway to connecting people and establishing genuine relationships, and I want to know how to better support people with autism to do this.
Could you explain the technology behind eye-tracking pupillometry? What can it tell us about an individual, and why is it an important tool?
Pupillometry is the measurement of pupil size over time. The pupil becomes bigger or smaller in response to a complex but finite set of inputs, including emotional stimuli. For example, when you are happy or scared your pupils dilate (become bigger), and the dilation is proportional to how happy or scared you are (i.e. more dilation with more emotion). Eye-tracking pupillometry is a relatively new technology as eye-tracking itself (which involves recording where someone is looking) has only been used during the past ten years or so.
Eye-tracking pupillometry is a great technology to use with young children with autism as it is non-invasive (no electrodes need to be attached to participants, like is needed with heart rate recording), is less affected by bodily movement than other systems (which can be problematic as this creates artifacts in data), and researchers can simultaneously measure where a person is looking (so they can know for sure what participants are responding to). This technology involves simply watching stimuli on a computer monitor, thus can be used to provide insight into the emotional life of non-verbal children, which made up the majority of the children in this study.
How does familiarity affect emotion processing in individuals with typical development? How does this compare to individuals with autism?
It is well known that individuals with typical development respond to the emotional expressions of familiar people in a different way than those of unfamiliar people. For example, when an old friend gives you a big smile, this expression carries with it more meaning and relevance than a smile of a complete stranger. Humans have a tendency to be more empathic towards and more accurate in perceiving emotions of in-group members than out-group members, whatever ‘group’ that may be, though this can be modified with exposure and empathic understanding of out-group members.
Not much was already known specifically on this topic, as this was the first study to examine the processing of emotion expressed by familiar people in individuals with autism. That said, we knew from Kristelle Hudry and colleagues’ 2009 study on empathy that children with autism, like their typically developing peers, are more empathic towards caregivers than unfamiliar adults. Also, in my clinical and personal experience I have seen many examples of ‘normal’ emotional responses in people with autism to their family members despite difficulty with emotional responding to unfamiliar people.
What were the key findings of your study, and were you surprised by any of these?
Using eye-tracking pupillometry, we measured the emotional responses of a group of children with autism and a group of typically developing children whilst they watched emotional expressions of their childcare teachers and therapists (i.e. familiar people) and people that they did not know. We found that the children with autism and the typically developing children had the same magnitude of pupillary response to familiar people expressing emotion. However, the children with autism had a reduced response to emotion expressed by unfamiliar people, compared to the typically developing children. Therefore the children with autism had a ‘normal’ magnitude of emotional reaction to familiar, but not unfamiliar people.
We also measured the timing (latency) of these emotional responses, finding that no matter whether the person expressing the emotion was familiar or unfamiliar, the children with autism had a delayed pupillary response compared to the typically developing group. This result suggests that people with autism take longer to react to emotional expressions than their peers. We think this helps to explain the difficulties that people with autism face during social encounters, which are fast-paced and ever changing.
Finally, we measured how long the children looked at the eye and mouth regions of the face, to see whether children with autism paid less attention to the eye region. Abnormal attention to the eye is a distinctive feature of autism, but interestingly we did not find this to be the case. Consistent with a previous study in 2011 by Vivanti and colleagues, we found that this result depended on whether the face showed emotion (fear) or not (a neutral face), with no difference in attention to emotional faces and less attention to the eye (and mouth) region of neutral faces. We think this result means that emotion helped to sustain the attention of the children with autism, who characteristically look less to faces than their peers in everyday life.
What do your results suggest about the neurological basis of autism?
We think that these results suggest that people with autism do not have a fundamentally different brain ‘wiring’ for emotion processing, as these brain circuits can be assessed or ‘bootstrapped’ by familiarity; they can process emotions of familiar people just like their peers. Although they have difficulty processing emotion expressed by the human face (as well as the human voice and body), this is easier for them with people they know. This may be because they experience emotional connectedness only to people they know well, rather than with people in general, as they have more experience with familiar faces or perhaps as they have more motivation to process the emotions of familiar people, or a combination of these three – the mechanism is still unclear.
However, the finding of a general delayed emotion response in the children with autism is suggestive of less strengthened connections between core brain centers for emotion and other brain areas, which has been found in previous studies in individuals with autism during emotion processing.
Where do you see the future of eye-tracking studies heading in the next ten years?
In the next ten years, I expect to see many more researchers using eye-tracking pupillometry in combination with the traditional attention measures that the eye-tracker provides. Many researchers have incorporated eye-tracking in their research paradigms but at the moment expertise in pupillometry is not that common. I would like to see (and be a part of) conferences dedicated to this methodology. I recently gave a presentation explaining some features of eye-tracking pupillometry at the International Conference on Infant Studies in Berlin, Germany; there seemed to be much interest in this methodology.
How can studies such as yours impact upon the clinical assessment and management of autism?
As direct clinical assessment of people with autism is often conducted by people who are unfamiliar to the individual, these results highlight the importance of obtaining parent or teacher reports of the individual interacting with familiar people in order to get an accurate perception of the person with autism’s strengths in emotion perception and reactivity.
Also, we think that our results in this study speak to the importance of establishing long-term therapeutic relationships with people with autism; therapists that become familiar to people with autism can provide more learning opportunities to foster their development of emotion perception and understanding.