Sensitivity, Over-Stimulation, Fear

I heard somewhere that ~%20 of a given population of creatures (mammals? animals? insects??) are relatively "more sensitive" than the rest of the population. I guess some have suggested that this is (somehow) some kind of evolutionary/genetic adaptation of a population; that having a certain percentage sensitive members in a population is a survival adaptation. Canary in the coal mine sort of thing. Ataraxia might be the opposite of this.

If a given person were generally "more sensitive" (over-sensitive, hypersensitive), then heshe would probably be more prone to a number of maladies; e.g., anxiety and panic attack. I wonder if hypersensitivity would also make a person more perceptive in at least some ways; this seems to be the general idea. Also, I wonder if this would have anything to do with intelligence . . . I tend to think of intelligence and perception (perspicuity?) as being linked. 007.

Been thinking about the relationship between anxiety and stimulation, stimulation in general. The notion that over-stimulation is a definition for anxiety. A stimulation could be just about any experience, where some experiences are more stimulating than others. So, sitting quietly, with a quiet mind, alone in a quiet, comfortable room would not be very stimulating at all; whereas, free running through the downtown of a busy city with a group of friends while playing hand-held video games and listening to an ipod would be very stimulating. Thinking really hard could be stimulating. Anyhow, I've noticed that if I reduce the stimulating events in my life, my general level of stress and anxiety seems to go down. This makes sense, but I'm surprised at how, in some way, almost everything I do has some "stimulation value". It also seems as though my threshold for stimulation is lower than it used to be, so that I'm more easily over-stimulated.

As an aspect of anxiety, fear seems ever present. A few things I might have noticed about anxiety and fear:

• There are really two fears: the fear "coming from" the anxiety, and the fear of the anxiety. The second can easily "feedback" into the first, so that the fear of the anxiety can make me more anxious (which makes me more afraid...).
• The fear which comes from the anxiety itself, or the "original fear" is also fear of something, but the fear is coming from somewhere deep in my psyche, something seeded there a long time ago. This would be a subconscious (below the radar or consciousness) reaction, a learned response to a similar type of situation or experience which my mind/body are supplying to "take care of the situation" without my having to work through it again. This is something I'm doing all the time, unconsciously.