Perception and Discrimination of Emotional Faces in Children with Autism Spectrum Disorders

Background: It has been indicated that individuals with ASD demonstrate marked abnormalities in the processing of faces and facial expressions. However, the literature on face processing in ASD has so far been largely mixed. Objectives: Our study aims to investigate emotional face processing and discrimination in children with ASD, mental retardation (MR) and typically developing (TD) children in China. Methods: 17 children with ASD, 22 children with mental retardation (MR) and 28 typically developing (TD) children attended two experiments. In experiment one, their gaze behavior was measured via an integrated T120 120 HZ eye tracker (Tobii Systems) when they watched videos of sad, happy and neutral faces (one female actress and one male actor). A multi-factor repeated measurements ANOVA with factors area of interest (AOI) (all areas, background, body, face, eyes, mouth), emotion (happy, sad, neutral) and group (ASD, TD, MR) was applied to gaze fixation durations. Experiment two is emotion discrimination task, which participants were required to choose one matched picture with the target one from six emotional faces (happy, angry, sad, surprised, afraid, disgusted). And the emotional faces were also presented in four different types (normal, inverted, blurred, inverted and blurred). Results: Significant difference was found on the average length of the face fixations of happy video (F(2.64)=6.08, p=0.004), with prolonged fixations for TD (3246 ms, SD 1083 ms) compared to those with ASD (4298 ms, SD 781 ms; p=0.002). When a face fixation of neutral video did occur, the time taken to make fixation on the square containing the face differed significantly between groups (F(2.64)=25.04, p<0.001). It was also found that the individuals with ASD spent less time viewing face of sad video than TD (p=0.001), and MR spent less time than TD (p=0.021), but ASD and MR did not differ (p=0.550). Contrary to some former results, this study showed that there was no significant difference on the amount of time fixating on the eyes of happy videos between ASD and TD (p=0.991), but MR had prolonger fixations than TD (p=0.022) and ASD had less fixation duration than MR (p=0.038). There was a significant effect of groups on faces of happy, neutral and sad video, but the effects disappeared when using blurred or inverted or inverted and blurred images. Conclusions: A central feature of ASD is an impairment in social attention, such as the eyes and face. Our results confirmed the former findings that the impairment in ASD may not be a unitary phenomenon. We also found that Chinese children with ASD and MR are able to understand and respond to emotions and their discrimination abilities do not differ from their TD peers.