The effect of ambient sounds on decision-making and heart rate variability in autism
Authors: Bellamy Rachel , Ring Howard , Watson Peter , Kemp Andrew , Munn Giles , Clare Isabel CH 
Published: June 2021

Autistic people report difficulties with the demands of a neurotypical world, but little research has assessed the impact of the environment on such difficulties. We investigated the effect of ambient sounds on decision-making and heart rate variability. Adults without intellectual disability were allocated to autistic ( n = 38) or neurotypical ( n = 37) groups matched on age, intellectual functioning and self-reported gender. Participants completed a shopping decision-making task in three randomly ordered sound conditions: no sound, non-social shopping sound (e.g. fridges humming) and social shopping sound (e.g. people talking). Decision-making latency, decision-making consistency, and heart rate variability were measured. Participants also provided qualitative reports of their experiences. Qualitative analyses indicated that autistic participants experienced (1) the non-social and social sound conditions more negatively than the no sound condition and (2) the social sound condition more negatively than neurotypical participants. However, there were no statistically significant differences in decision-making latency, decision-making consistency, or heart rate variability across sound conditions and participant groups. Further research should consider alternative quantitative measures to explore subjective experience to help understand further which aspects of the environment autistic people are sensitive to, in turn, enabling more evidence-based autism-friendly changes to be made. Lay abstract Many autistic people report difficulties making decisions during everyday tasks, such as shopping. To examine the effect of sounds on decision-making, we developed a supermarket task where people watched a film shown from the shopper’s perspective and were asked to make decisions between different products. The task was divided into three sections and participants completed each section in a different auditory environment: (1) no sounds, (2) non-social sounds (e.g. fridges humming) and (3) social sounds (e.g. people talking). Thirty-eight autistic and 37 neurotypical adults took part. We measured decision-making by examining how long it took to make a decision and how consistent people were with their decisions. We also measured heart rate variability because this biological response provides a measure of anxiety. After the supermarket shopping task, participants told us in their own words about their experiences. Autistic participants said that they found the non-social and social sound conditions more difficult than the no sound condition, and autistic participants found the social sound condition more negative than neurotypical participants. However, decision-making and heart rate variability were similar for autistic and neurotypical participants across the sound conditions, suggesting that these measures may not have been sensitive enough to reflect the experiences the autistic participants reported. Further research should consider alternative measures to explore the experiences reported by autistic people to help us understand which specific aspects of the environment autistic people are sensitive to. This, in turn, may enable more specific and evidence-based autism-friendly changes to be made.