Autistic and non-autistic people express emotions differently through their facial movements, according to a new study, which may help to explain why emotional expressions are sometimes misinterpreted between the two groups.
In a landmark study mapping facial expressions among autistic and non-autistic individuals, researchers at the University of Birmingham used detailed facial motion tracking to create an extensive library of facial expressions linked to major emotions such as anger, happiness and sadness, with more than 265 million data points.
The study, published in Autism Research, involved 25 autistic and 26 non-autistic adults, who produced nearly 5000 expressions in total. Each participant produced angry, happy and sad facial expressions in two ways – in synchrony with some sounds, and while speaking. The team found differences in angry, happy, and sad facial expressions between the groups, with autistic participants also producing more unique expressions:
- For anger, the autistic participants relied more on the mouth, and less on the eyebrows, than their non-autistic peers;
- For happiness, the autistic participants showed a less exaggerated smile that also did not "reach the eyes"; and
- For sadness, the autistic participants produced a downturned expression by raising their upper lip more than their non-autistic peers.
The team also found that alexithymia – a 'sub-clinical' condition commonly found in autism that involves difficulties identifying and describing one's own emotions – also shaped facial expressions. Alexithymia was linked to less clearly distinct angry and happy expressions, making them more likely to appear ambiguous.
Dr Connor Keating, who conducted the research at the University of Birmingham and is now based in the Department of Experimental Psychology at the University of Oxford said: "Our findings suggest autistic and non-autistic people differ not only in the appearance of facial expressions, but also in how smoothly these expressions are formed. These mismatches in facial expressions may help to explain why autistic people struggle to recognise non-autistic expressions and vice versa."
Professor Jennifer Cook, senior author of the paper from the University of Birmingham, said: "Autistic and non-autistic people may express emotions in ways that are different but equally meaningful — almost like speaking different languages. What has sometimes been interpreted as difficulties for autistic people might instead reflect a two-way challenge in understanding each other's expressions. We are currently investigating this idea, so watch this space for updates."
The project was funded by the Medical Research Council (MRC, United Kingdom) and the European Union's Horizon 2020 Research and Innovation Programme.
