Differences Between Autistic and Non-Autistic Individuals in Audiovisual Speech Integration: A Systematic Review and Meta-analysis.

Research has indicated unique challenges in audiovisual integration of speech among autistic individuals, although methodological differences have led to divergent findings. We conducted a systematic literature search to identify studies that measured audiovisual speech integration among both autistic and non-autistic individuals. Across the 18 identified studies (combined N = 952), autistic individuals showed impaired audiovisual integration compared to their non-autistic peers (g = 0.69, 95% CI [0.53, 0.85], p <.001). This difference was not found to be influenced by participants' mean ages, studies' sample sizes, risk-of-bias scores, or paradigms investigated. However, a subgroup analysis suggested that child studies may show larger between-group differences than adult ones. The prevailing pattern of impaired audiovisual speech integration in autism may have cascading effects on communicative and social behavior. However, small samples and inconsistency in design/analysis translated into considerable heterogeneity in findings and opacity regarding the influence of underlying unisensory and attentional factors. We recommend three key directions for future research: larger samples, more research with adults, and standardization of methodology and analytical approaches.

Age, not autism, influences multisensory integration of speech stimuli among adults in a McGurk/MacDonald paradigm.

Differences between autistic and non-autistic individuals in perception of the temporal relationships between sights and sounds are theorized to underlie difficulties in integrating relevant sensory information. These, in turn, are thought to contribute to problems with speech perception and higher level social behaviour. However, the literature establishing this connection often involves limited sample sizes and focuses almost entirely on children. To determine whether these differences persist into adulthood, we compared 496 autistic and 373 non-autistic adults (aged 17 to 75 years). Participants completed an online version of the McGurk/MacDonald paradigm, a multisensory illusion indicative of the ability to integrate audiovisual speech stimuli. Audiovisual asynchrony was manipulated, and participants responded both to the syllable they perceived (revealing their susceptibility to the illusion) and to whether or not the audio and video were synchronized (allowing insight into temporal processing). In contrast with prior research with smaller, younger samples, we detected no evidence of impaired temporal or multisensory processing in autistic adults. Instead, we found that in both groups, multisensory integration correlated strongly with age. This contradicts prior presumptions that differences in multisensory perception persist and even increase in magnitude over the lifespan of autistic individuals. It also suggests that the compensatory role multisensory integration may play as the individual senses decline with age is intact. These findings challenge existing theories and provide an optimistic perspective on autistic development. They also underline the importance of expanding autism research to better reflect the age range of the autistic population.

Perception of temporal synchrony not a prerequisite for multisensory integration.

Temporal alignment is often viewed as the most essential cue the brain can use to integrate information from across sensory modalities. However, the importance of conscious perception of synchrony to multisensory integration is a controversial topic. Conversely, the influence of cross-modal incongruence of higher level stimulus features such as phonetics on temporal processing is poorly understood. To explore the nuances of this relationship between temporal processing and multisensory integration, we presented 101 participants (ranging from 19 to 73 years of age) with stimuli designed to elicit the McGurk/MacDonald illusion (either matched or mismatched pairs of phonemes and visemes) with varying degrees of stimulus onset asynchrony between the visual and auditory streams. We asked them to indicate which syllable they perceived and whether the video and audio were synchronized on each trial. We found that participants often experienced the illusion despite not perceiving the stimuli as synchronous, and the same phonetic incongruence that produced the illusion also led to significant interference in simultaneity judgments. These findings challenge the longstanding assumption that perception of synchrony is a prerequisite to multisensory integration, support a more flexible view of multisensory integration, and suggest a complex, reciprocal relationship between temporal and multisensory processing.

A New Real-Life Test for Reciprocity in Autistic Adults: The Interactive Drawing Test.

Impaired social-emotional reciprocity is a defining feature of Autism Spectrum Disorder (ASD). Deficits in reciprocity can be difficult to assess, particularly in adults with average or above average intelligence. The recently developed Interactive Drawing Test (IDT) measures reciprocity in children and adolescents with and without ASD based on spontaneous non-verbal interactions during the joint creation of a drawing. In this study, we examined if the IDT is able to differentiate between 19 normally intelligent adults with ASD and 18 without ASD. The IDT total reciprocity score, including the number of meaningful contributions to objects initially drawn by the examiner, was lower in the autistic adults compared to those without ASD. By assessing both the quantity and quality of spontaneous reciprocal behavior, the IDT was able to identify subtle differences in reciprocal behavior of adults with and without ASD with average intelligence. Even though a larger sample is required to determine its psychometric properties, the IDT appears a promising tool to enrich the diagnostic process of ASD in adults. Impaired social-emotional reciprocity is a defining feature of Autism Spectrum Disorder (ASD). The clinical field lacks sensitive tests for assessing impaired reciprocity. The recently developed Interactive Drawing Test (IDT) for reciprocity was tested in autistic and non-autistic adults. During the IDT, an examiner and participant make a joint drawing, taking turns, without specifying what they will draw. We aimed to investigated whether autistic adults showed less reciprocal behavior on the IDT compared to non-autistic participants. Autistic participants were less likely to jointly draw with the examiner, in particular when the examiner initiated a topic. The IDT revealed subtle but characteristic differences in reciprocal behavior related to ASD, suggesting it may be a promising diagnostic tool.