Psychometric Properties at the Item Level of the Japanese Version of the Highly Sensitive Person Scale: A Partial Credit Model Analysis

Environmental sensitivity is an umbrella concept that describes the individual differences in how people perceive and process environmental stimuli and experiences, in both negative and positive contexts. The Highly Sensitive Person Scale (HSPS) is widely used to assess sensory processing sensitivity, a temperamental marker of environmental sensitivity. However, item-level characteristics of the Japanese version of the HSPS (HSPS-J19) have not been sufficiently examined. Using item response theory (IRT), we evaluated the item characteristics of the HSPS-J19 in a sample of 1,626 Japanese adults. We fitted the partial credit model and estimated category threshold parameters and item-fit statistics for each item. Threshold parameters generally indicated that higher levels of the latent trait were required to endorse higher response categories. For some items, however, adjacent thresholds were not ordered as expected, suggesting that distinctions between response categories may not have been sufficiently clear. Item-fit statistics suggested that the three items corresponding to the Aesthetic Sensitivity subscale showed a poor fit. Overall, this IRT-based item analysis provides additional information on the psychometric properties of the HSPS-J19 that is not readily captured by classical test theory or factor-analytic approaches.