- 1. The quality of being sensitive, in various senses of the adj.
- 2. The activity and experience of the senses.
- 3. a. The degree to which a device, test, or procedure responds to small amounts of or slight changes in that to which it is designed to respond; the ratio of the response of a device to the stimulus causing it; = SENSITIVENESS 3.
- b. spec. in Radio, (a measure of) the ability of a receiver or other part of a radio system to pick up or respond to weak radio signals.
- 4. Psychol. Used attrib., esp. in sensitivity group, training, to denote training in small groups aimed at increasing a person's awareness of the behaviour, feelings, and motives of others and of himself. Cf. T-group s.v. T 7.
A highly sensitive person (HSP) is a person having the innate trait of high sensitivity (or innate sensitiveness as Carl Gustav Jung originally coined it). According to Elaine N. Aron and colleagues as well as other researchers, highly sensitive people, which would represent about a fifth of the population, process sensory data much more deeply and thoroughly due to a biological difference in their nervous systems. This is a specific trait with key consequences that in the past has often been confused with innate shyness, inhibitedness, innate fearfulness, introversion, and so on.  The existence of the trait of innate sensitivity was demonstrated using a test that was shown to have both internal and external validity. Although the term is primarily used to describe humans, the trait is present in nearly all higher animals.
The term highly sensitive person was coined by Dr. Elaine N. Aron in 1996, and the name is gaining popularity because it presents the trait in a positive light. It posits that shyness, inhibitedness, and fearfulness may or may not be acquired by highly sensitive people and animals, depending on environmental challenges. Yet other names used to describe the trait in literature include "introverted emotional temperament", "chronic cortical/cortisol arousal", "hypervigilance", and "innate shyness".
A number of books have been written on the topic, for example "Help Is On Its Way" by Jenna Forrest, which is endorsed by Psychologist Elaine Aron and Author, Coach Eva Gregory and "The Highly Sensitive Person's Survival Guide" with forward by Elaine Aron and "The Highly Sensitive Person's Companion" by Ted Zeff, Ph.D. which is in English, French, Dutch, Japanese, Polish and Danish.
Dr. Aron describes the opposite end of the spectrum, "the opposite of a Highly Sensitive Person (HSP) is a person who takes many risks, that is, acts without reflecting very much. An HSP who is an HSS (High Sensation Seeker) also will find ways to have lots of new experiences, but won't take a lot of unreflected-upon risks." She also cites studies involving other animals ranging from mammals to houseflies and goldfish.
The approach adopted by Aron and colleagues questions the role of notions such as "shyness" in explaining basic differences in behavior that are encountered in many species, including humans. As opposed to shyness, which is constructed both as a negative trait and a genetic weakness that can be worsened by circumstances, the trait of high sensitivity is considered a basic, evolutionarily conserved trait with survival advantages in itself. Zoologists observed the existence of a shy-bold continuum in animal species:
... in sunfish a "shy-bold continuum" has been identified, in which "bold" individuals differ from "shy" ones in their propensity to approach novel objects (including minnow traps), eat certain food items, and acclimate to laboratory environments. The "shy-bold continuum" has also been observed in humans and several other mammals. Zoologists are aware that notions of shyness and boldness are anthropomorphic (as exemplified by the use of quotation marks, above; "personality" is another term used with quotation marks). Some animals and even insects were shown to get survival advantages (avoidance of dangers) and even, as a consequence, reproductive advantages (availability for "exuberant" courtships behaviours)" from being "shy". Faced with this apparent misnaming of a basic survival strategy, Aron and colleagues developed the notion of high sensitivity, expanding on Jung's suggestion of the trait innate sensitiveness, which he distinguished from his own notion of introversion. In support of this distinction, Aron showed that the Highly Sensitive Person Scale identified a sizable proportion of extroverted sensitive persons (30%). In addition, Aron provides evidence supporting that highly sensitive persons can also be highly sensitive to favourable social cues and respond with traits of extroversion.
The research on sensory-processing sensitivity, however, builds on Eysenck's views on introversion and arousal and Gray's work on the inhibition system. This research in turn builds on Pavlov's work on sensory response to both physical and mental over-stimulation, and work by Jung and his contemporaries differentiating extroverted and introverted cognitive sensitivity types.  This research shows that about 15-20% of humans and higher animals have a nervous system that is more sensitive to subtleties. This means that regular sensory information is processed and analyzed to a greater extent, which contributes to creativity, intuition, sensing implications and attention to detail, but which may also cause quick over-stimulation and over-arousal.
This temperament may also have some correlation with continuously high cortisol levels, which may cause hypervigilance and susceptibility to trauma, or the same traumas may encourage hypervigilance, which in turn may contribute to high cortisol. Being highly sensitive may amplify or create psychological issues when over-arousal occurs. The ability to unconsciously or semi-consciously process environmental subtleties often contributes to an HSP seeming "gifted" or possessing a "sixth sense". Sensitiveness is often confused with shyness, but 30% of HSPs have extroverted personalities. Another common misconception is that only females can be HSPs; there are roughly the same number of male HSPs as female. The percentage appears to hold true for all animals possessing this trait."
Attributes and characteristics
HSP students work differently from others. They pick up on the subtle things, learning better this way than when overaroused. If an HSP student is not contributing much to a discussion, it does not necessarily mean they do not understand or are too shy. HSPs often process things better in their heads or they may be over-aroused. This can be the reason for their not contributing. HSPs are usually very conscientious but underperform when being watched. This also applies to work situations; HSPs can be great employees — good with details, thoughtful and loyal, but they do tend to work best when conditions are quiet and calm. Because HSPs perform less well when being watched, they may be overlooked for a promotion. HSPs tend to socialize less with others, often preferring to process experiences quietly by themselves. 
Contrast with Dabrowski's over-excitability
Readers interested in HSP may want to compare and contrast Aron's approach with Dabrowski's concept of over-excitability in his theory of Positive Disintegration.
As explained above, many writers on HSP propose a positive, accepting attitude towards [being an] HSP. However, this is not the general consensus in the professional psychological community. For instance, Jeffrey E. Young, founder of the increasingly applied Schema Therapy, although never having been critical of HSP writers or writings, links high sensitivity, or as he calls it, the "highly empathic temperament", with the Self Sacrifice Schema (Young, 2003, p. 246-251), which in turn is almost always related to the Emotional Deprivation Schema. In his opinion, these persons (patients) need to learn to focus on themselves instead of others and to learn to get their own needs met, needs they typically are not aware of. As such, HSP can be seen not as a positive personality trait, but as a psychopathological condition that can be treated with experiential, cognitive, behavioral, and limited-reparenting strategies.
Sources and notes
- Ketay, S., Hedden, T., Aron, A., Aron, E., Markus, H., & Gabrieli, G. (2007, January). The personality/temperament trait of high sensitivity: fMRI evidence for independence of cultural context in attentional processing. Poster presented at the annual meeting of the Society for Personality and Social Psychology, Memphis, TN. Summary by Aron (2006): "A functional study comparing brain activation in Asians recently arrived in the United States to European-Americans found that in the nonsensitive, different areas were activated according to culture during a difficult discrimination task known to be affected by culture, but culture had no impact on the activated areas for highly sensitive subjects, as if they were able to view the stimuli without cultural influence."
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- Aron, E.N. The Clinical Implications of Jungs Concept of Sensitiveness , Journal of Jungian Theory and Practice, 8,2006, 11-43.
- WebMD Live Events Transcript The Highly Sensitive Person In Love with Elaine Aron
- Aron, Elaine. 1996. The Highly Sensitive Person. ISBN 0-553-06218-2.
- Aron, Elaine and Aron, Arthur. 1997. Sensory-Processing Sensitivity and Its Relation to Introversion and Emotionality, Journal of Personality and Social Psychology. Aug. 1997 Vol. 73, No. 2, pp. 345-368.
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- Aron, E. N. (2004). "Revisiting Jung's Concept of Innate Sensitiveness." Journal of Analytical Psychology, 49, 337-367.
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- Aron, Elaine. 1999. The Highly Sensitive Person's Workbook. ISBN 0-7679-0337-4.
- Aron, Elaine. 2000. The Highly Sensitive Person in Love. ISBN 0-7679-0336-6.
- Aron, Elaine. 2002. The Highly Sensitive Child. ISBN 0-7679-0872-4.
ed. Bates, J. and Wachs, T. Temperamented: Individual Differences in the Biological Aspects of Temperament. ISBN 1-55798-222-8.
- Mesich, Kyra. 2000. The Sensitive Person's Survival Guide. ISBN 0-595-09800-2.
- Mandel, Debra. 2003. Healing the Sensitive Heart. ISBN 1-58062-708-0.
- Jaeger, Barrie. 2004. Making Work Work for the Highly Sensitive Person. ISBN 0-07-140810-X.
ed. Wachs, T., and King, B. Behavioral Research in the Brave New World of Neuroscience and Temperament. ISBN 1-55798-222-8.
- Zeff, Ted. 2004. The Highly Sensitive Person's Survival Guide. ISBN 1-57224-396-1.
- Young, Jeffrey E. et al. 2003. Schema Therapy: a practitioner's guide ISBN 1-57230-838-9
- Joyful Work for Sensitive People
- Help Is On Its Way: A Memoir About Growing Up Sensitive - Resource for Emotional Development of Sensitive Kids.
- Highly Sensitive Person Highly Sensitive Person [HSP] Information, Characteristics, Research and Resources
- PDF Research paper Jawer, Mr. Michael (2005) Environmental Sensitivity: A Neurobiological Phenomenon?.
- Are You Highly Sensitive? A Self-Test
- Is Your Child Highly Sensitive? Parent's test