What does science say?
In fact, the brains of highly sensitive people show a higher amount of activity when they work on a specific task or process input.
Moreover, one of the areas that showed significantly more acitivity, was the amygdala. This is the area in the brain responsible for identifying fear and preparing for emergency situations.
In detail, this area in the brain is strongly developed amongst highly sensitive people.
As a result, when a HSP receives much sensory input, they emotionally experience it more intensely.