Highly sensitive person

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This article is about the psychology term. For the book by Elaine Aron, see The Highly Sensitive Person.

Highly sensitive person (abbreviated HSP; sometimes capitalized Highly Sensitive Person in the popular press[1][2]) is the psychology term first popularized in the mid-1990s to denote a person having a high measure of the innate trait whose scientific name is sensory processing sensitivity (SPS). Here, sensory processing refers to what occurs as sensory information is transmitted to or processed in the brain.[3] SPS is measured by the Highly Sensitive People Scale (HSPS),[3] which can be divided into subscales.[4][5]

Highly sensitive people, who comprise about 15-20% of the population,[6] process sensory data more deeply due to the biological nature of their nervous systems.[7] This depth of processing underlies HSPs' greater proclivity to overstimulation, emotional reactivity and empathy, and sensitivity to stimuli.[2]

Origin and development of the term HSP[edit]

The phrase "highly sensitive person" had been used before the 1990s, such as colloquially to denote the opposite of "tough"[8] or even technically as an indication of affective sensitivity (empathy).[9] However, in the mid-1990s Drs. Elaine and Arthur Aron first formally identified sensory processing sensitivity (SPS), the scientific term for high sensitivity, as the defining trait of highly sensitive persons.[1] In the context of HSPs, sensory processing refers not to what occurs within the sense organs themselves, but as sensory information is transmitted to or processed in the brain.[3] Studies have shown that HSP brain scans show differences in neural activity compared with non-HSPs.[1]

In 2015 The Wall Street Journal's Elizabeth Bernstein wrote that HSPs were "having a moment," noting that several hundred research studies had been conducted on topics related to HSPs' high sensitivity, and that a First International Scientific Conference on High Sensitivity or Sensory Processing Sensitivity had been held at the Vrije Universiteit Brussel.[1]

Attributes and characteristics of HSPs[edit]

The sensory processing sensitivity (SPS) that defines HSPs has been described as "a temperament/personality trait characterized by social, emotional and physical sensitivity."[10] More specifically, HSP attributes have been summarized[2][11] by the mnemonic DOES: Depth of processing, Overstimulation because of the depth of processing, Emotional reactivity and empathy, and Sensitivity to stimuli.

HSPs have been described as having qualities of low risk taking, need for quiet (usually alone), high motivation to avoid overstimulation, preference for deeply meaningful conversations, greater awareness of subtleties in emotional and non-verbal communication, and a sense of being different and not the ideal.[12] HSPs are thought to embody a strategy of thoroughly processing information about a novel situation before acting (exploring psychologically), as distinguished from a strategy of novelty seeking (advancing immediately and exploring physically).[12]

Practical implications for the individual HSP[edit]

High sensory processing sensitivity (SPS) has been found to increase the influence of environment on affective (emotional) outcomes, for both negative[13][14] and positive[15] influences and outcomes.

HSPs' deeper processing of and greater responsiveness to both positive and negative stimuli motivates learning, and often leads to more successful responses in similar situations in the future.[16] However, this deeper processing does not clearly manifest as an outwardly observable behavior, contributing to both laymen and health professionals wrongly misattributing SPS to traits thought to be undesirable, such as neuroticism, shyness, inhibition, unlikeability and lack of intelligence.[16]

Like other socially reticent behavior[17] with which it is often confused,[13][16] sensitivity has been linked to lack of peer acceptance and has even been associated with deviance, at least in Western culture.[17] This social and cultural unacceptability adds to fear of social evaluation and other environmental stressors, and can result in lower self-esteem for HSPs.[13] In particular, the stress of an adverse childhood environment is thought to lead to greater negative affectivity for adult HSPs than for non-HSPs of similar backgrounds.[13]

HSP students pick up on subtleties and may think about them a long time before demonstrating their grasp of a subject. If an HSP student is not contributing much to a discussion, it does not necessarily mean he or she does not understand or is too shy. HSPs often have insights they are afraid to reveal because they differ from the common view, or because speaking up is too over arousing for them.[citation needed]

In a work environment, HSPs can be good with details, thoughtful and loyal, but tend to work best when conditions are quiet and calm.[18] 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.[19]

Measuring sensitivity, and the HSP category[edit]

In 1997 Drs. Elaine N. Aron and Arthur Aron formally published the Highly Sensitive People Scale (HSPS), consisting initially of 27 questions such as "Are you easily overwhelmed by strong sensory input?" and "Do you tend to be more sensitive to pain?"[3] Aron and Aron reported acceptable reliability coefficients (α = .85 or .87) for the HSPS as a unidimensional measure of SPS, as well as content, convergent, and discriminant validity.[3]

Smolewska et al. (2006) demonstrated that Aron's unidimensional HSPS was a valid and reliable measure of SPS, and further that the scale can be divided into a three-component structure including Aesthetic Sensitivity, Low Sensory Threshold, and Ease of Excitation.[4]

Evans and Rothbart (2008)[5] extracted two orthogonal constructs from the HSPS, namely, negative affect (having a sensory discomfort sub-construct) and orienting sensitivity (described[20] in 2007).

At the time of The Highly Sensitive Person (1996), E. Aron had inferred from Jerome Kagan's studies of inhibitedness in children, that high sensory processing sensitivity (high SPS) should define a qualitatively distinct category,[21] an inference supported by accumulated research (N>2000 as of 2012) indicating HSP Scale score patterns are distributed like an approximately dichotomous categorical variable and not continuously in a single normal distribution.[16] This early (1996) lack of direct evidence was filled by a separate 2012 study (N=898 subjects) in which three taxometric methods evidenced SPS as a categorical variable (warranting a category qualitatively distinguishing HSPs from non-HSPs) rather than a dimensional variable (which would have implied HSPs differ from non-HSPs merely as a matter of degree).[22]

Background and underlying principles[edit]

Evolutionary foundations[edit]

The sensory processing sensitivity trait defining HSPs is explained in part by the evolutionary development in various species of two personality types that manifest distinct survival strategies, namely, '‘pausing before acting’' (allow neural processes to assess survival-related subtleties in the environment), and '‘acting first'’ (to respond quickly to opportunities and discover survival-relevant cues through motor exploration).[10] Humans are among more than 100 species found empirically to have subpopulations of individuals who both coexist and consistently display respectively different levels of responsiveness to environmental stimuli.[23] An evolutionary basis for this phenomenon has been explained through negative frequency dependence (explaining coexistence) and when costs of responsiveness are lower for individuals who have previously been more responsive (explaining consistency).[23]

After reviewing studies from the 1970s through the early 1990s concerning innate shyness, adult introversion, and childrens' inhibitedness, as well as similar traits in non-human species, Drs. Elaine and Arthur Aron reported seven studies and formally introduced (1997) sensory processing sensitivity (SPS) as a "core variable" thought to underlie the two complementary evolutionary survival strategies ("quiet vigilance" versus "exploration") activated in the face of novel stimulation.[3] Aron and Aron posited that, like already-recognized gender-based and timid-versus-bold[24][25] survival strategies, these two HSP-based survival strategies constitute an end product of natural selection rather than its raw material.[3]

Psychological foundations[edit]

Early research had confirmed that, consistent with the diathesis–stress model, high sensory processing sensitivity (SPS) increased the correlation between negative environmental influences (such as adverse parenting) and negative affective outcomes (such as adult shyness).[13] Despite the traditional focus of psychiatric genetics on negative concepts of environmental adversity and genetic vulnerability,[26] the differential susceptibility hypothesis suggested (2009) that high SPS would also increase correlation between positive environmental influences and positive affective outcomes.[14] In such subsequent studies, high innate SPS was found to allow HSPs to be more responsive to positive environmental influences than non-HSPs.[15] For example, in studies reported in 2013, only children scoring in the upper third of the HSP Scale experienced a decrease in depression symptoms in response to a school's resilience-promoting program in a deprived metropolitan area; and emotional affects of HSPs were found more responsive to the emotional reward of successfully completing tests.[15]

More broadly, SPS research may be considered to refine the "personality-situation debate"—the personality theory embodiment of the larger nature versus nurture debate; the SPS research indicates that high innate sensory processing sensitivity (nature) is what underlies HSPs' greater responsiveness to their environments (nurture).[16]

Neural foundations[edit]

To study the neural foundations of sensory processing sensitivity (SPS), functional magnetic resonance imaging (fMRI) technology was used to determine whether stronger neural activity would be found in predicted brain regions in response to both positive and negative social stimuli.[27] Greater activity was found in HSPs' brain regions involved in attention, empathy, higher order cognitive processing, action planning in response to "close others" (non-strangers; particularly to their positive emotions), integration of sensory information, emotional meaning making, self-other processing, the mirror neuron system, and self-awareness.[27]

These positive findings for neural responses to social stimuli paralleled results of the first (2011) fMRI neural investigation of SPS, which found SPS to correlate with both increased response time and increased brain-region activation in response to subtle changes in non-social stimuli (specifically, a change-detection task involving landscape photographs).[10] Still other fMRI testing confirmed greater regional brain activation during culturally non-preferred tasks, with higher-SPS subjects showing little cultural difference, indicating HSPs' judgments are based on more thorough processing of actual stimuli and less by cultural context.[28]

Genetic foundations and innateness[edit]

Sensory processing sensitivity (SPS) has been indicated to be substantially innate (of genetic origin) as opposed to learned (of environmental origin).[27] For example, studies show SPS' association with polymorphisms of a variant of the 5-HTTLPR (serotonin-transporter-linked polymorphic region),[29] and relate contributions to SPS from polymorphisms in dopamine neurotransmitter genes (accounting for 15% of the variance in HSP measurement compared to 2% for the tested environmental factor, stressful life events).[30]

Related concepts[edit]

The sensory processing sensitivity (SPS) concept was intended to encompass what adult personality researchers have variously described as: weak nervous system (Pavlov), low screening (Mehrabian), augmenting (of stimulation; Petrie), reducing (of evoked potential; Buchsbaum, Haier, & Johnson), reactivity (Strelau), avoidance temperament (Elliot & Thrash), and nondisinhibition or reflectivity (Patterson & Newman), and what child temperament researchers have described as inhibitedness (Kagan), infant (or innate) shyness (Cheek & Buss; Daniels & Plomin), reactivity (Rothbart; Strelau), and threshold of responsiveness (Thomas & Chess).[13] SPS has also been related to innate sensitiveness (Jung),[7] arousal focus (Feldman), and the physiological differences underlying introversion and extroversion (Eysenck; Stelmack; Stelmack & Geen).[13] Other concepts of the trait include coping style, reactivity, flexibility, plasticity, and differential susceptibility.[23]

Aron, Aron, & Jagiellowicz reviewed in 2012[16] how SPS theory builds on Eysenck's views on introversion and arousal, and on Gray's work on the behavioral inhibition system (BIS; although the idea that the BIS is equivalent to a system leading to fearful or withdrawing behaviors has been repudiated by Gray, who reconceptualized it as a system that allows pausing to check before acting on both threats and opportunities).[31][32]

Evans and Rothbart's orienting sensitivity[20] constituted one of the two orthogonal constructs that could be extracted from Aron's HSP Scale (HSPS).[5]

Research in developmental psychology provides evidence that individuals differ in their sensitivity. According to the differential susceptibility hypothesis by Belsky (1997b; 1997a; 2005) individuals vary in the degree they are affected by experiences or qualities of the environment to which they are exposed. Showing that children thought to have difficult temperaments in infancy were merely more susceptible to the effects of both low- and high-quality child care before age 5,[33][34] Pluess & Belsky used the term vantage sensitivity to describe the trait and to highlight its evolutionary advantages.[15]

Distinguishing HSPs[edit]

According to the model of sensory processing sensitivity (SPS) that defines HSPs, variations in SPS underlie various trait differences such as introversion versus extraversion, inhibited versus uninihibited (children), and timid versus bold survival strategies, but SPS itself—modeled as the basic variable rather than a secondary variable—is itself distinct from these traits.[3]

Distinguish: shy people[edit]

Aron posited that shyness, inhibition, and fearfulness, terms often used to describe some HSPs, may or may not be acquired by them, depending entirely on environmental stressors.[13]

Distinguish: Dabrowski's over-excitability[edit]

HSPs' high sensitivity contrasts with Dabrowski's concept of over-excitability in his theory of Positive Disintegration.

Distinguish: introverts[edit]

Elaine Aron responded to Susan Cain's 2012 book Quiet: The Power of Introverts in a World That Can't Stop Talking and its related Time cover story[35] by stating that Cain was in fact describing highly sensitive persons (defined[3] in terms of sensory processing sensitivity) and not introverts (which Aron says is recently becoming defined[36] more narrowly in terms of social interaction).[37] Though Aron wrote that Cain and others blurred the lines between sensitivity and introversion, Aron called the Time article "a huge, huge step" for understanding HSPs, and that as more is learned, the 30%[36] of HSPs who are social extroverts will be better understood.[37]

Distinguish: high sensation seekers (HSS)[edit]

Although HSSs may seem to be the opposite of HSPs, a person who takes many risks acts without reflecting very much is the opposite of an HSP; an HSP who is also an HSS will find ways to have novel experiences without taking ill-considered risks.[38]

Distinguish: sensory processing disorder[edit]

HSPs' defining trait, sensory processing sensitivity (SPS), is "unrelated"[16] to sensory processing disorder.

Cross-species incidence[edit]

Although the term "high sensitivity" is primarily used to describe humans, something similar to the trait is present in over 100 other species.[23][39]

Sources and notes[edit]

  1. ^ a b c d Bernstein, Elizabeth (May 18, 2015). "Do You Cry Easily? You May Be a ‘Highly Sensitive Person’". The Wall Street Journal. Archived from the original on June 1, 2015. 
  2. ^ a b c Lally, Maria (October 12, 2015). "Highly sensitive people: a condition rarely understood". The Telegraph (U.K.). Archived from the original on October 18, 2015. 
  3. ^ a b c d e f g h i Aron, Elaine; Aron, Arthur (1997). "Sensory-Processing Sensitivity and its Relation to Introversion and Emotionality" (PDF). Journal of Personality and Social Psychology 73 (2): 345–368. doi:10.1037/0022-3514.73.2.345. Archived (PDF) from the original on May 13, 2015. 
  4. ^ a b Smolewska, Kathy A.; McCabe, Scott B.; Woody, Erik Z. (2006). "A psychometric evaluation of the Highly Sensitive Person Scale: The components of sensory-processing sensitivity and their relation to the BIS/BAS and "Big Five"". Personality and Individual Differences 40 (6): 269–1279. doi:10.1016/j.paid.2005.09.022. 
  5. ^ a b c Evans, David E.; Rothbart, Mary K. (January 2008). "Temperamental sensitivity: Two constructs or one?". Personality and Individual Differences 44 (1): 108–118. doi:10.1016/j.paid.2007.07.016. 
  6. ^ Aron, Elaine (1996). The Highly Sensitive Person, Preface at page xiii.
  7. ^ a b Aron, E.N. (2006). "The Clinical Implications of Jung's Concept of Sensitiveness". Journal of Jungian Theory and Practice 8: 11–43. Archived from the original (PDF) on January 17, 2016.  Discussion re nervous system is, inter alia, in "Prelude to Research" at p. 14.
  8. ^ See, for example, Duka, John (March 28, 1981). "Evangeline Gouletas: She Enjoys Her Business and Her Privacy". The New York Times. Archived from the original on May 24, 2015.  ("I am not a tough person at all," she said. "I lead people and I am highly sensitive to their needs. I am strong and disciplined and there is a big difference between that and being tough." ... Of Governor Carey, she would say only: "I think he is a highly sensitive person as well.")
  9. ^ Campbell, Robert J.; Kagan, Norman; Krathwohl, David R. (September 1971). "The development and validation of a scale to measure affective sensitivity (empathy)". Journal of Counseling Psychology 18 (5): 407–412. doi:10.1037/h0031492. (Most discriminating items contained correct answer statements describing fairly strong client emotions. The highly sensitive person accurately identified the statement but the person low in sensitivity was attracted to a moderate or neutral statement.) 
  10. ^ a b c Jagiellowicz, J.; Xu, X.; Aron, A.; Aron, E.; Cao, G.; Feng, T.; Weng, X. (2011). "Sensory processing sensitivity and neural responses to changes in visual scenes" (PDF). Social Cognitive and Affective Neuroscience (SCAN) 6: 38–47. doi:10.1093/scan/nsq001. Archived (PDF) from the original on July 12, 2013. 
  11. ^ Aron, Elaine N. (Apr 27, 2011). "Chapter 2: Assessing for High Sensitivity". Psychotherapy and the Highly Sensitive Person: Improving Outcomes for That Minority of People Who Are the Majority of Clients. Routledge. ISBN 9781135967567. 
  12. ^ a b Mashek, Debra J. (co-editor); Aron, Arthur (co-editor) (February 13, 2004). Handbook of Closeness and Intimacy (First ed.). Psychology Press. pp. 279–280. ISBN 978-0805842852.  "Temperament and Intimacy" chapter by Aron.
  13. ^ a b c d e f g h Aron, E. N.; Aron, A.; Davies, K. (2005). "Adult shyness: The interaction of temperamental sensitivity and an adverse childhood environment" (PDF). Personality and Social Psychology Bulletin 31: 181–197. doi:10.1177/0146167204271419. Archived (PDF) from the original on July 15, 2014. 
  14. ^ a b Belsky, Jay; Pluess, Michael (2009). "Beyond Diathesis Stress: Differential Susceptibility to Environmental Influences" (PDF). Psychological Bulletin 135 (6): 885–908. doi:10.1037/a0017376. Archived (PDF) from the original on December 7, 2010. 
  15. ^ a b c d Pluess, Michael; Belsky, Jay (2013). "Vantage Sensitivity: Individual Differences in Response to Positive Experiences" (PDF). Psychological Bulletin 139 (4): 901–916. doi:10.1037/a0030196. Archived (PDF) from the original on January 26, 2016. 
  16. ^ a b c d e f g Aron, E.; Aron, A.; Jagiellowicz, J. (2012). "Sensory processing sensitivity: A review in the light of the evolution of biological responsivity" (PDF). Personality and Social Psychology Review 16 (3): 262–282. doi:10.1177/1088868311434213. Archived (PDF) from the original on May 13, 2015. 
  17. ^ a b Chen, Xinyin; Rubin, Kenneth H.; Sun, Yuerong (1992). "Social Reputation and Peer Relationships in Chinese and Canadian Children: A Cross-cultural Study" (PDF). Child Development 63: 1336–1343. doi:10.1111/j.1467-8624.1992.tb01698.x. Archived from the original on February 1, 2016. 
  18. ^ Bhavini Shrivastava. "Predictors of work performance for employees with sensory processing sensitivity" September 2011, MSc Organizational Psychology, City University, London, Department of social sciences, Psychology
  19. ^ Aron, Elaine. 1996. The Highly Sensitive Person, ISBN 0-553-06218-2.
  20. ^ a b Evans, D. E.; Rothbart, M. K. (2007). "Development of a model for adult temperament". Journal of Research in Personality 41: 868–888. doi:10.1016/j.jrp.2006.11.002. 
  21. ^ "We Do Exist as a Distinct Set of People" in "Author's Note" to 2012 Edition of Aron, Elaine N. The Highly Sensitive Person (PDF). Archived (PDF) from the original on August 17, 2014. 
  22. ^ Borries, Franziska; Ostendorf, Fritz (2012). "Sensory-Processing Sensitivity – Dimensional or Categorical Variable? A Taxometric Investigation" (PDF). University of Bielefeld (Germany).  (Archive of January 24, 2016.)
  23. ^ a b c d Wolf, Max; Van Doorn, G. Sander; Weissing, Franz J. (2008). "Evolutionary emergence of responsive and unresponsive personalities" (PDF). PNAS 105 (41): 15825–15830. doi:10.1073/pnas.0805473105. Archived from the original on January 28, 2016. 
  24. ^ Wilson, DS; Clark, AB; Coleman, K; Dearstyne, T (1994). "Shyness and boldness in humans and other animals". Trends in Ecology & Evolution 9 (11): 442–446. doi:10.1016/0169-5347(94)90134-1. 
  25. ^ Hedrick AV (2000). "Crickets with extravagant mating songs compensate for predation risk with extra caution". Proc. Biol. Sci. 267 (1444): 671–5. doi:10.1098/rspb.2000.1054. PMC 1690585. PMID 10821611. 
  26. ^ Belsky, J.; Jonassaint, C; Pluess, M; Stanton, M; Brummett, B; Williams, R (2009). "Vulnerability genes or plasticity genes?" (PDF). Molecular Psychiatry 14: 746–754. doi:10.1038/mp.2009.44. Archived (PDF) from the original on June 6, 2012. 
  27. ^ a b c Acevedo, Bianca P.; Aron, Elaine N.; Aron, Arthur; Sangster, Matthew-Donald; Collins, Nancy; Brown, Lucy L. (2014). "The highly sensitive brain: an fMRI study of sensory processing sensitivity and response to others’ emotions". Brain and Behavior 4 (4): 580–594. doi:10.1002/brb3.242. Archived from the original on June 23, 2014. 
  28. ^ Aron, A.; Ketay, S.; Hedden, T.; Aron, E.; Markus, H. R.; Gabrieli, J. D. E. (2010). "Temperament trait of sensory processing sensitivity moderates cultural differences in neural response, Special Issue on Cultural Neuroscience" (PDF). Social Cognitive and Affective Neuroscience (SCAN) 5 (2-3): 219–226. doi:10.1093/scan/nsq028. Archived (PDF) from the original on April 23, 2013. 
  29. ^ Licht, C., Mortensen, E. L., & Knudsen, G. M. (2011). Association between sensory processing sensitivity and the serotonin transporter polymorphism 5-HTTLPR short/short genotype. Biological Psychiatry, 69, supplement for Society of Biological Psychiatry Convention and Annual Meeting, abstract 510.
  30. ^ Chen, C.; Chen, C.; Moyzis, R.; Stern, H.; He, Q.; Li, H.; Dong, Q. (2011). "Contributions of dopamine-related genes and environmental factors to Highly Sensitive Personality: A multi-step neuronal system-level approach". PLoS ONE 6: e21636. doi:10.1371/journal.pone.0021636. Archived from the original on February 4, 2016. 
  31. ^ McNaughton, N.; Gray, J. A. (2000). "Anxiolytic action on the behavioral inhibition system implies multiple types of arousal contribute to anxiety". Journal of Affective Disorders 61: 161–176. doi:10.1016/s0165-0327(00)00344-x. 
  32. ^ Amodio, M. D.; Master, L. S.; Yee, M. C.; Taylor, E. S. (2008). "Neurocognitive components of the behavioral inhibition and activation systems: Implications for theories of self-regulation". Psychophysiology 45: 11–19. doi:10.1111/j.1469-8986.2007.00609.x. 
  33. ^ Pluess, M.; Belsky, J. (2009). "Differential Susceptibility to Rearing Experience: The Case of Childcare". Journal of Child Psychology and Psychiatry and Allied Disciplines 50 (4): 396–404. doi:10.1111/j.1469-7610.2008.01992.x. 
  34. ^ Pluess, M.; Belsky, J. (2010). "Differential Susceptibility to Parenting and Quality Child Care". Developmental Psychology 46 (2): 379–90. doi:10.1037/a0015203. PMID 20210497. 
  35. ^ Walsh, Bryan, "The Upside Of Being An Introvert (And Why Extroverts Are Overrated)" (WebCite archive), Time, February 6, 2012.
  36. ^ a b Aron, Elaine N., Ph.D, "Understanding the Highly Sensitivity Person: Sensitive, Introverted, or Both? | Extraverted HSPs face unique challenges" (WebCite archive), Psychology Today, July 21, 2011.
  37. ^ a b Aron, Elaine N., Ph.D, "Time Magazine: "The Power of (Shyness)" and High Sensitivity" | ... Quiet describes HSPs (WebCite archive), Psychology Today, February 2, 2012.
  38. ^ The Highly Sensitive Person In Love with Elaine Aron", WebMD Live Events Transcript, dated before September 27, 2007, archive.org's earliest archive.
  39. ^ While many animals are sensitive to specific stimuli, it seems that others demonstrate a broader sensitivity, plasticity, or flexibility. For example, Sih and Bell (2008) wrote that enough examples exist "to suggest that individual difference in environmental and social sensitivity is common, potentially quite important, and worthy of further study" (p. 16). Dingemanse and colleagues (2009) provide an integrative model for observing personality traits (e.g., shy, bold, aggressive, nonaggressive) that in some species or individuals are inflexible and completely specific to context but in other cases are flexible, occurring in some contexts and not in others, according to its usefulness, so that the underlying trait in these cases would be being sensitive enough to know when to be sensitive—suggesting layers of processing. ● Dingemanse, J. N.; Kazem, A. J. N.; Reale, D.; Wright, J. (2009). "Behavioral reaction norms: Animal personality meets individual plasticity". Trends in Ecology & Evolution 25: 81–89. doi:10.1016/j.tree.2009.07.013. Sih, A.; Bell, A. M. (2008). "Insights for behavioral ecology from behavioral syndromes.". Advances in the Study of Behavior 38: 227–281. doi:10.1016/s0065-3454(08)00005-3. 

Further reading[edit]

  • Aron, Elaine; Aron, Arthur (1997). "Sensory-Processing Sensitivity and Its Relation to Introversion and Emotionality". Journal of Personality and Social Psychology 73 (2): 345–368. doi:10.1037/0022-3514.73.2.345. 
  • Bruch, M.; Gorsky, J.; Cullins, T.; Berger, P. (1989). "Shyness and Sociability Reexamined: A Multicomponent Analysis". Journal of Personality and Social Psychology 57 (5): 904–15. doi:10.1037/0022-3514.57.5.904. 
  • Deo, P.; Singh, A. (1973). "Some Personality Correlates without Awareness". Behaviorometric 3: 11–21. 
  • Gough, H., & Thorne, A., "Positive, negative, and balanced shyness: Self-definitions and the reactions of others" in Shyness: Perspectives on Research and Treatment ISBN 0-306-42033-3.
  • Higley, J., & Suomi, S. "Temperamental Reactivity in Non-Human Primates" in Temperament in Childhood ed. Kohnstramm, G., Bates, J., and Rothbart, M. (New York: Wiley, 1989), 153–67.
  • Kagan, J.; Reznick, J.; Snidman, N. (1988). "Biological Bases of Childhood Shyness". Science 240 (4849): 167–71. doi:10.1126/science.3353713. PMID 3353713. 
  • Thorne, A. (1989). "The Press of Personality: A Study of Conversations Between Introverts and Extraverts". Journal of Personality and Social Psychology 53: 713–26. doi:10.1037/0022-3514.53.4.718. 
  • Raleigh, M.; McGuire, M.; Brammer, GL; Yuwiler, A (1984). "Social and Environmental Influences on Blood Serotonin and Concentrations in Monkeys". Archives of General Psychiatry 41 (4): 181–90. doi:10.1001/archpsyc.1984.01790150095013. PMID 6703857. 
  • Revelle, W.; Humphreys, M.; Simon, L.; Gilliland, K. (1980). "Interactive Effect of Personality, Time of Day, and Caffeine: A Test of the Arousal Model". Journal of Experimental Psychology General 109 (1): 1–13. doi:10.1037/0096-3445.109.1.1. PMID 6445402. 
  • Zumbo, B.; Taylor, S. (1993). "The Construct Validity of the Extraversion Subscales of the Meyers-Briggs Type Indicator". Canadian Journal of Behavioral Science 25 (4): 590–604. doi:10.1037/h0078847. 
  • Belsky, J.; Pluess, M. (2009). "Beyond Diathesis-Stress: Differential Susceptibility to Environmental Influences". Psychological Bulletin 135 (6): 885–908. doi:10.1037/a0017376. PMID 19883141. 

External links[edit]