Stop Making Noise! Auditory Sensitivity in Adults with Autism Spectrum Disorder: Physiological Habituation and Subjective Detection Threshold.

Background: One of the most commonly reported sensory sensitivities in ASD is sensitivity to sounds (e.g., Haesen et al., 2011). However, possible underlying mechanisms are still unknown. Some suggest that habituation might play a role, while others postulate that altered sensory detection thresholds might be an explanatory mechanism. So far, studies on auditory habituation show mixed results and focused mainly on ASD children (e.g., for review see Lydon et al., 2014). Altered sensory detection thresholds have been shown in ASD children (e.g., Tavasolli et al., 2015). Research on auditory detection thresholds in ASD adults is, however, limited.

Objectives: We examined whether ASD adults habituate slower and have lower auditory detection thresholds compared to typically developing (TD) adults. We also examined whether habituation and detection threshold are related to self-reported auditory sensitivities.

Methods: We included 33 ASD and 31 TD adults (25-45 years; IQ>70). Habituation is defined the number of trials until on two consecutive trials no skin conductance response (SCR; >0.03 uS; Boucsein et al., 2012) was given to a simple tone (1000Hz) and a Dutch ambulance siren. Detection threshold is measured by decreasing the volume of a simple tone until participants report not to hear the tone anymore. This is repeated until participants reach the same threshold twice. The self-reported auditory sensitivity is measured with the adolescent adult sensory profile (AASP).

Results: A MANOVA analysis revealed that the groups (N=24 each) did not differ on predefined habituation for both tone (p=.96; Cohen’s d=.02) and siren (p=.92; Cohen’s d=.03). There was also no significant Pearson correlation between habituation and self-reported auditory sensitivity (N=48; r=.02; p=.90). The groups also did not differ on auditory detection thresholds (N_ASD=33; N_TD=31; p=.20; Cohen’s d=.32). There was, however, a significant correlation between detection thresholds and self-reported auditory sensitivity (N=64; r=.29; p=.02). Moreover, exploratory repeated measures analyses revealed that when habituation was defined as decreasing SCR amplitudes (Boucsein et al., 2012) that ASD adults had a significantly slower decline in SCR amplitude compared to ASD adults (p=.04; Cohen’s d=0.64). Regarding the siren, no significant differences were found.

Conclusions: At first sight, no large differences between ASD and TD adults were observed on habituation and auditory detection threshold, but a higher auditory detection threshold did seem to be related to more self-reported auditory sensitivity. At second sight, concluding that no differences emerge between the groups might be premature as our exploratory analyses revealed that the intensity of the physiological response to auditory stimuli might remain heightened in ASD. Hence, it seems to depend on how habituation is operationalized whether or not one can conclude that ASD adults habituate slower than TD adults.