Sensory Processing Sensitivity (SPS) is considered a temperament or personality trait. It refers to a person's sensitivity to subtle environmental stimuli, the depth and intensity with which these stimuli are processed, and the impact this has in terms of emotional and physiological reactivity (e.g., the extent to which a person is easily disturbed by crowds and chaotic situations and the consequent need to withdraw and unwind). A highly sensitive person is characterised by a (greatly) increased degree of SPS. Since the existing limited scientific research suggested that there is a link between high SPS and the development of mental and physical symptoms (such as fatigue), we conducted a number of studies on how the concept is measured, and what the possible link is with (other) personality traits and some clinical outcomes.

In a first study, the psychometric properties of the Dutch version of the Highly Sensitive Person Scale (HSPS) developed by Aron and Aron (1997) were explored in a general population sample (N=998), a sample of patients suffering from (chronic) fatigue complaints (N=340), and a sample of chronic pain patients (N=337). Results demonstrated that the scale was a valid and reliable measure of the ‘Sensory Processing Sensitivity’ construct. A bi-factor model, consisting of a general sensitivity factor and three separate factors, provided the best fit to the data in each sample. The three separate factors, capturing different dimensions of sensory processing sensitivity, were labelled ‘Ease of Excitation’, ‘Sensory and Aesthetic Sensitivity’, and ‘Low Sensory Threshold’. Distinct patterns of associations were found between these factors and the Big Five personality traits (De Gucht et al., 2023).

During the validation process of the HSPS it became apparent that this scale offers a restricted perspective on the Sensory Processing Sensitivity concept. Based on the current literature, several different dimensions can be distinguished within this concept, namely (1) (heightened) sensitivity to (subtle) sensory stimuli, including neutral perceptual sensitivity to both internal and external stimuli, affective sensitivity, and associative sensitivity, (2) sensory discomfort, and (3) emotional or physiological reactivity. The fact that these dimensions are not adequately covered by the HSPS developed by Aron & Aron (1997) was the starting point for study 2, focusing on the development of a more comprehensive scale, the Sensory Processing Sensitivity Questionnaire (SPSQ). The item pool generated for the development of the SPSQ consisted of 60 items. After exploratory factor analysis, 43 items remained, divided into six specific factors: (1) Sensory Sensitivity to Subtle Internal and External Stimuli, (2) Emotional and Physiological Reactivity, (3) Sensory Discomfort, (4) Sensory Comfort, (5) Social-Affective Sensitivity, and (6) Aesthetic Sensitivity. Confirmatory factor analysis indicated that a higher-order bi-factor model consisting of two higher-order factors (a positive and negative dimension), a general sensitivity factor and six specific factors had the best fit. Strong positive associations were found between Emotional and Physiological Reactivity, the negative higher-order dimension, and Neuroticism; the same holds for the association between Aesthetic Sensitivity, the positive higher-order dimension, and Openness. Emotional and Physiological Reactivity and the negative higher-order dimension showed clear associations with clinical outcomes (i.e., anxiety, depression, somatic complaints, and fatigue) (De Gucht et al., 2022).

With 43 items, the SPSQ is an extensive questionnaire. Incorporating such a questionnaire in research including multiple variables may lead to surveys becoming quite long. One of the problems with long surveys is that they often result in lower response rates, which can have an impact on the generalizability of the findings due to non-response bias. For this reason, we decided to develop a short form (study 3), similar in content and structure to the original scale, and possessing strong psychometric qualities. Such an abbreviated version of the SPSQ has the advantage of measuring many both positive and negative characteristics of SPS and doing so using a limited number of items. The Short Form (SPSQ-SF) was developed using a split-sample validation design. Within a large selection sample, items were retained based on impact on internal consistency reliability, fit to the hierarchical structure of the original SPSQ, and information curves based on a Graded Response Model. In the replication sample, the dimensionality and fit to the latent structure of the SPSQ were evaluated. The results of our study indicate a good fit of the SPSQ-SF. It is strongly correlated to the original SPSQ. Convergent, discriminant and concurrent validity was established in relation to other instruments measuring aspects of SPS, Big Five personality traits and clinical outcomes, respectively (De Gucht & Woestenburg, manuscript submitted for publication).