Table 1 Description, examples, and measurement of the levels of the five-level taxonomy of sensory-relevant constructs

Sensory-related neural excitability

The size, variability, latency, or degree of change, in a measurable brain response following sensory stimulation

The difference in ERP following the presentation of a 1000 Hz pure tone played from 0 to 70 dB in 5 dB steps

Sensory stimulation during the application of neuroimaging methods such as fMRI, fNIRS, EEG and MEG. Peripheral evoked potentials (e.g. auditory evoked potentials or peripheral nerve conduction methods may also be of relevance)

Most studies which have assessed sensory-related neural excitability have used a combination of custom paradigms and commercial equipment

Perceptual sensitivity

How well an individual is able to detect and discriminate between stimuli

Detection Hearing the sirens of a passing fire truck

Psychophysical paradigms (e.g. 2AFC, 2IFC or MCS approaches in which participants are required to report whether they do or do not detect (or in which interval they do or do not detect) a stimulus of a given intensity across a range of trials

Examples of “off the shelf” tools for assessing perceptual sensitivity include:

German Research Network on Neuropathic Pain [43]

Von Frey Hairs [44]

Audiometers which include pure-tone testing (e.g. see [45])

The University of Pennsylvania Smell Identification test [46]

The Sniffin’ sticks test from Burghardt [47]

Certain measures from the Sensory Integration and Praxis Tests (SIPT; [48])

Certain measures from the Evaluation in Ayres Sensory Integration (EASI; [49])

The NIH Somatosensory Toolbox [50]

Vibrotactile psychophysical assessments conducted using Cortical Metrics stimulators (e.g. [51])

Psychophysical experiments can also be custom programmed in free-to-use, purpose-built software such as PsychoPy [52]. However, additional peripheral equipment may be required

Questionnaires specifically designed to assess perceptual sensitivity:

Sensory Perception Quotient (SPQ; [53])

Discrimination Accurately differentiating between a light touch and forceful physical contact

Psychophysical paradigms (e.g. 2AFC, 2IFC or MCS approaches in which participants are required to report whether they are able to discriminate between two simultaneously or sequentially presented stimuli

Temporal judgement

Psychophysical paradigms (e.g. 2AFC, 2IFC or MCS approaches in which participants are required to judge which of two stimuli were presented first [i.e. order judgement] or which of two stimuli were presented for more or less time [i.e. duration discrimination])

Other

Perceptual sensitivity has other domains beyond detection, discrimination, and temporal judgement. There are also many other psychophysical paradigms that can be used to assess the low-level sensory processes that give rise to perception such as adaptation and habituation. Description and explanation of these additional domains and paradigms is beyond the scope of the article

Physiological reactivity to sensory input

Refers to how much an individual displays changes in relevant bodily processes in reaction to sensory input

Pupil dilation in response to sensory stimulation

Physiological measurements of near-automatic responses to sensory input (e.g. pupil dilation, galvanic skin responses, cortisol levels and skin conductance)

Most studies which have assessed physiological reactivity to sensory input have used custom paradigms coupled with commercial equipment

Affective reactivity to sensory input

Refers to how an individual appraises and reacts to sensory input

Feeling uncomfortable and startled after hearing the sirens of the fire truck driving by

Experiencing distress in reaction to certain textures or smells of a given meal

Questions which specifically ask autistic individuals how they feel about certain sensory stimuli without making reference to how they choose to respond are ideal. Similar questions directed at parents and clinicians may also be used (see main text for a discussion about limitations)

Performance-based measures administered by clinicians could also be used to observe how children react on an affective level to sensory stimuli

Some of the available questionnaires with items probing affective reactivity to sensory input include:

Sensory Profile and its various iterations [54, 55]

Sensory Experience Questionnaire (SEQ; [56])

Sensory Processing Measure (SPM; [57])

Glasgow Sensory Questionnaire (GSQ; [58])

Sensory Sensitivity Questionnaire (SSQ; [59])

Clinician administered performance-based measures include:

Sensory Processing Scale Assessment (SP3D; [60])

The Sensory Challenge Protocol (see [61] for details)

Tailor made tasks to assess participant-reported pleasantness ratings in reaction to tactile stimuli, administered by trained researchers or clinicians, have also been used. For some examples, see [62] and [63]

Behavioural responsivity to sensory input

Refers to how an individual responds (or chooses not to respond) to sensory input they may find discomforting or pleasurable

Avoidance of loud and bright environments (sometimes referred to as “sensory avoidance”)

Seeking of certain smells or textures one finds comforting (sometimes referred to as “sensory seeking”)

Questions which specifically ask autistic individuals or their caregivers how they or the autistic individual in reference responds to certain sensory stimuli. Ideally, such questions should help determine whether behavioural responses are due to a) affective discomfort or b) restricted and repetitive interest, as the latter may not be a sensory-specific behaviour per se.

Administered tasks or stimuli followed by clinical observation may also be used

Given that currently available questionnaires contain items that assess both Affective reactivity to sensory input and behavioural responsivity to sensory input, we refer readers to the questionnaire in the cell above for currently available measures of this level

Clinician administered performance-based measures include:

Sensory Assessment for Neurodevelopmental Disorders (SAND; [64])