Fig. 1

Example models depicting associations between the hierarchical levels of the taxonomy. Circles have been used to symbolize levels, with different colours referring to specific levels of the hierarchical taxonomy. Labels for each level presented on the left-hand side. Four different examples of possible models are presented. a The first model is the implied model from the hierarchy of the taxonomy. It suggests that interindividual differences in sensory-related neural excitability, perhaps due to increased excitation-inhibition balance [142], explains alterations of perceptual sensitivity (for example, see [143]). Alterations of perceptual sensitivity, in turn, result in changes in physiological reactivity to sensory input, which in turn drives affective reactivity to sensory input. Changes in affective reactivity to sensory input then impact behavioural responsivity to sensory input. Note that behavioural responsivity to sensory input may also be affected by other variables not directly related to sensory differences (e.g. interindividual differences in self-agency and strategies used to accommodate for sensory differences) and are hence not included in the visual schematic. b An alternative model which discounts any impact of sensory-related neural excitability. Increased affective hyperreactivity to sensory input might be due to differences in amygdala, hippocampus, and orbital-frontal cortex activation reported in autism (see work by Green and colleagues [144]). Given that perceptual sensitivity can change as a function of affect (e.g. experimentally induced acute stress can lower thermal sensitivity of the skin [145]), alterations of perceptual sensitivity could simply due to affective hyperreactivity to sensory input. Physiological reactivity to sensory input is simply a consequence of altered perceptual sensitivity. Behavioural responsivity to sensory input is driven by altered perceptual sensitivity (as is often assumed). c A similar model to model (a), however, a feedback loop is introduced between affective reactivity to sensory input and perceptual sensitivity. Here, perceptual sensitivity is initially altered by differences in neural excitability to sensory input, but is then later exacerbated by affective hyperreactivity to sensory input, a concept introduced in model (b). d Sensory-related neural excitability and perceptual sensitivity are related but are independent to the relationship between physiological- and affective reactivity to sensory input, and behavioural responsivity to sensory input. This model is plausible based on clinical observations of autistic individuals who have affective hyperreactivity to sensory input but do not show differences in perceptual sensitivity