Facial expression coding in children and adolescents with autism: Reduced adaptability but intact norm‐based coding

Abstract

Individuals with autism spectrum disorder (ASD) can have difficulty recognizing emotional expressions. Here, we asked whether the underlying perceptual coding of expression is disrupted. Typical individuals code expression relative to a perceptual (average) norm that is continuously updated by experience. This adaptability of face-coding mechanisms has been linked to performance on various face tasks. We used an adaptation aftereffect paradigm to characterize expression coding in children and adolescents with autism. We asked whether face expression coding is less adaptable in autism and whether there is any fundamental disruption of norm-based coding. If expression coding is norm-based, then the face aftereffects should increase with adaptor expression strength (distance from the average expression). We observed this pattern in both autistic and typically developing participants, suggesting that norm-based coding is fundamentally intact in autism. Critically, however, expression aftereffects were reduced in the autism group, indicating that expression-coding mechanisms are less readily tuned by experience. Reduced adaptability has also been reported for coding of face identity and gaze direction. Thus, there appears to be a pervasive lack of adaptability in face-coding mechanisms in autism, which could contribute to face processing and broader social difficulties in the disorder.

Adaptation to the Speed of Biological Motion in Autism

“…In this study, we compared autistic and typical participants, of similar age and ability, on the adaptive coding of the speed of biological motion. We hypothesised that autistic individuals' atypicalities in the adaptive coding of facial stimuli (Ewing et al 2013a;Lawson et al 2018;Pellicano et al 2013;Rhodes et al 2018;Rutherford et al 2012) should generalise to non-facial social stimuli and predicted that autistic participants should show less adaptation to the speed of the PLDs of our task than the typical comparison participants. We found that both groups showed significant adaptation effects-but, contrary to our prediction, that the magnitude of adaptation was comparable in autistic and typical participants.…”

“…It is thus also very important to control for attention in adaptation studies (see also gaze-contingent paradigms; e.g., Wilms et al 2010). To our knowledge, controlling for attention has been employed in earlier studies on adaptation in autism by Ewing et al (2013b) on face identity, Karaminis et al (2015) on perceptual causality, Lawson et al (2018) on eye-gaze direction and Rhodes et al (2018) on facial expression. Our study on adaptation to the running speed of biological motion in autism is novel in combining the use of a secondary attention task with eye-tracking.…”

“…With regard to social stimuli, attenuated adaptation in autism has been observed consistently within the face-processing domain, including, for example, for facial identity in autistic children (Ewing et al 2013b;Pellicano et al 2007) and relatives of autistic children (Fiorentini et al 2012), for facial configuration (Ewing et al 2013a, b) and eye-gaze direction in children (Pellicano et al 2013) and adults (Lawson et al 2018), and for emotional expressions in children (Rhodes et al 2018) and adults (Rutherford et al 2012). van Boxtel et al (2016 also found that autistic children show reduced adaptation to action discrimination in biological motion (walking vs. running).…”

“…This was important as earlier studies have shown that attention modulates the size of adaptation (Kreutzer et al 2015;Rhodes et al 2011). Controlling for attention was achieved by employing a dual-task paradigm, in which the primary task measured the perception of biological motion and adaptive coding, while the secondary task motivated participants to attend to the middle of the screen and assessed their attention (see also Ewing et al 2013b;Karaminis et al 2015;Lawson et al 2018;Rhodes et al 2018). We also collected eye-movement data to quantify participants' looking preferences during the task.…”

Expression Recognition Difficulty Is Associated with Social But Not Attention-to-Detail Autistic Traits and Reflects Both Alexithymia and Perceptual Difficulty

“…Research into whether adaptive norm-based coding of expression is weakened in autistic people has produced mixed results. In one study, children and adolescents with autism showed weaker adaptive norm-based coding of expression than a typically-developing control group (Rhodes et al, 2017). This weakened adaptive norm-based coding showed a numerical association with greater severity scores on the Autism Diagnostic Observation Schedule (Lord et al, 2012) and Social Communication Questionnaire (Lord & Rutter, 2003), though these associations were non-significant in the relatively small sample.…”