What Does "Mushinkei" Reveal? — Did the Japanese Language Conceptualize the Non-HSP Before HSP Research Did?

The English word "insensitive" translates into Japanese as mushinkei — literally, "no nerves." This paper examines whether this somatic metaphor points to real individual differences in neural architecture related to Sensory Processing Sensitivity (SPS). It further proposes that Japanese speakers may have observed and linguistically encoded the low-sensitivity end of the sensitivity spectrum prior to Aron and Aron's (1997) formal conceptualization of the HSP. The paper connects this linguistic observation to existing neuroscience on empathy-related circuits and to the colloquial concept of "mental strength."