Time Perception in the Autism Spectrum Disorders Across Sensory Modalities

Background: Autism Spectrum Disorder (ASD) is primarily defined by difficulties in social interaction and communication. The causes of these difficulties are likely to be multifaceted and recent research suggests that abnormal temporal processing might play a critical role (Allman, 2011). Studies of time perception suggest that individuals with ASD are as accurate but less precise than typically developing (TD) individuals (Falter et al., 2012; Allman et al., 2011; Martin et al., 2010) in discriminating or reproducing temporal durations in the sub-second to second range. Few studies, however, have examined multisensory time processing in ASD, which one would expect to be most relevant to the temporal dynamics of social interaction. 

Objectives:

- Characterise time perception in ASD for durations relevant to social interaction

- Compare time perception in ASD in the visual, auditory and audiovisual modalities 

Methods: We tested 24 ASD and 22 TD adults on a time comparison task involving auditory, visual and audiovisual stimuli. Participants were presented with pairs of stimuli (a standard and a probe), and asked to decide which lasted longer. The standard duration was either 800 or 1200ms, and the probes were either ±5, 10, 25 or 50% of the standard. Trials involving the 800ms and 1200ms standards were presented in pseudo-random order but trials were blocked by modality. In the visual modality the stimulus was a light grey square, in the auditory modality it was a 440Hz pure tone and in the audiovisual condition both stimuli were presented simultaneously. 

Results: Half of the ASD individuals (N=12) performed very similar to the TD group, with participants overestimating probe durations in relation to the 800ms standard and underestimating them in relation to the 1200ms standard (as measured by shifts in the Point of Subjective Equality). In line with previous studies, the ASD group was less precise in their temporal judgements (as measured by the Weber Ratio, WR) and both groups demonstrated a lower WR in the visual as compared to the auditory and audio-visual modalities. However, the other half of ASD individuals (N=12) showed great difficulties with the task, particularly in the visual modality and for shorter durations. This latter group responded very quickly and follow-up measures are currently being collected to examine whether this might reflect heightened impulsivity and/or attenuated response inhibition. Importantly, across all ASD participants we observed a small but significant correlation between ADOS reciprocal-social-interaction scores and the extent to which individual data conformed to a discriminating as opposed to a chance performance profile. 

Conclusions: Our findings suggest that time perception is partly preserved but less precise in ASD for durations that are critical for social interaction. The difficulties were most pronounced in the visual modality and for durations below 1 s and correlated moderately with ADOS reciprocal-social-interaction scores. Imprecise time perception may hinder the understanding of others’ communicative behaviours and impact on speech-and-gesture coordination in ASD. Further studies are needed to understand what factors underly the timing imprecision in ASD, and to clarify the role of timing difficulties in social interaction and communication.