Origin
The construct of Sensory Processing Sensitivity (SPS) and its measure, the 27-item Highly Sensitive Person Scale, were introduced by Elaine Aron and Arthur Aron (1997). SPS describes a temperament trait characterised by deeper cognitive processing of stimuli, heightened emotional reactivity and empathy, greater awareness of subtle environmental cues, and a tendency toward overstimulation in intense settings.
What it measures
The HSPS indexes individual differences in sensitivity to internal and external stimulation. Factor-analytic work has suggested the scale captures sub-components often summarised as Ease of Excitation, Low Sensory Threshold, and Aesthetic Sensitivity (Smolewska, McCabe & Woody, 2006), though the trait is also frequently used as a single dimension.
Psychometric standing
Aron and Aron (1997) reported the scale's development and validity across multiple studies. Subsequent research has examined its factor structure and links to temperament and to differential susceptibility — the idea that highly sensitive individuals are more affected by both negative and positive environments (Pluess, 2015).
Reviewers note ongoing debate about whether sensitivity is best modelled as categorical "types" or as a continuous trait; current evidence favours a continuum.