1. "A shy man no doubt dreads the notice": Charles Darwin, The Expressions of the Emotions in Man and Animals (Charleston, SC: BiblioBazaar, 2007), 259.

2. Easter Sunday, 1939. The Lincoln Memorial: My description of the concert is based on film footage of the event.

3. And it wouldn't have, without Eleanor Roosevelt ... to sing at the Lincoln Memorial: Allida M. Black, Casting Her Own Shadow: Eleanor Roosevelt and the Shaping of Postwar Liberalism (New York: Columbia University Press, 1996), 4144.

4. "This was something unique": The American Experience: Eleanor Roosevelt (Public Broadcasting System, Ambrica Productions, 2000). See transcript: http://www.pbs.org/wgbh/amex/eleanor/filmmore/

transcript/transcript1.html.

5. They met when he was twenty: Blanche Wiesen Cook, Eleanor Roosevelt, Volume One: 18841933 (New York: Viking Penguin, 1992), esp. 125236. See also The American Experience: Eleanor Roosevelt.

6. her first scientific publication in 1997: Elaine N. Aron and Arthur Aron, "Sensory-Processing Sensitivity and Its Relation to Introversion and Emotionality," Journal of Personality and Social Psychology 3, no. 2 (1997): 34568.

7. When she was a girl ... She decided to find out: The biographical information about Aron comes from (1) interview with the author, August 21, 2008; (2) Elaine N. Aron, The Highly Sensitive Person: How to Thrive When the World Overwhelms You (New York: Broadway Books, 1996); (3) Elaine N. Aron, The Highly Sensitive Person in Love: Understanding and Managing Relationships When the World Overwhelms You (New York: Broadway Books, 2000).

8. First Aron interviewed thirty-nine people ... lightbulb burning a touch too brightly: Aron and Aron, "Sensory-Processing Sensitivity." See also E. N. Aron, "Revisiting Jung's Concept of Innate Sensitiveness," Journal of a.n.a.lytical Psychology 49 (2004): 33767. See also Aron, The Highly Sensitive Person.

9. They feel exceptionally strong emotions: In laboratory studies, looking at pictures designed to create strong positive or negative emotions, they reported feeling more emotionally aroused than nonsensitive people. See B. Acevedo, A. Aron, and E. Aron, "Sensory Processing Sensitivity and Neural Responses to Strangers' Emotional States," in A. Aron (Chair), High Sensitivity, a Personality/Temperament Trait: Lifting the Shadow of Psychopathology, symposium presented at the Annual Meeting of the American Psychological a.s.sociation, San Diego, California, 2010. See also Jadzia Jagiellowicz, Arthur Aron, Elaine Aron, and Turhan Canli, "Faster and More Intense: Emotion Processing and Attentional Mechanisms in Individuals with Sensory Processing Sensitivity," in Aron, High Sensitivity.

10. scientists at Stony Brook University: Jadzia Jagiellowicz et al., "Sensory Processing Sensitivity and Neural Responses to Changes in Visual Scenes," Social Cognitive and Affective Neuroscience, 2010, doi.10.1093/scan/nsq001.

11. echoes Jerome Kagan's findings: Jerome Kagan, "Reflection-Impulsivity and Reading Ability in Primary Grade Children," Child Development 363, no. 3 (1965): 60928. See also Ellen Siegelman, "Reflective and Impulsive Observing Behavior," Child Development 40, no. 4 (1969): 121322.

12. "If you're thinking in more complicated ways": Interview with the author, May 8, 2010.

13. highly empathic: Aron and Aron, "Sensory-Processing Sensitivity." See also Aron, "Revisiting Jung's Concept of Innate Sensitiveness." See also Aron, The Highly Sensitive Person. And see the following fMRI studies: Acevedo, "Sensory Processing Sensitivity and Neural Responses to Strangers' Emotional States." And see Jadzia Jagiellowicz, "Faster and More Intense: Emotion Processing and Attentional Mechanisms in Individuals with Sensory Processing Sensitivity." Note that many personality psychologists who subscribe to the "Big 5" theory of personality a.s.sociate empathy not with sensitivity (a construct that is gaining attention, but is relatively less well known than the Big 5), but with a trait known as "Agreeableness" and even extroversion. Aron's work does not challenge these a.s.sociations, but expands them. One of the most valuable aspects of Aron's work is how radically, and fruitfully, she reinterprets personality psychology.

14. tentatively a.s.sociated with sensitivity: Seth J. Gillihan et al., "a.s.sociation Between Serotonin Transporter Genotype and Extraversion," Psychiatric Genetics 17, no. 6 (2007): 35154. See also M. R. Munafo et al., "Genetic Polymorphisms and Personality in Healthy Adults: A Systematic Review and Meta-a.n.a.lysis," Molecular Psychiatry 8 (2003): 47184.

15. show them pictures of scared faces: David C. Funder, The Personality Puzzle (New York: W. W. Norton, 2010), citing A. R. Hariri et al., "Serotonin Transporter Genetic Variation and the Response of the Human Amygdala," Science 297 (2002): 400403.

16. faces of people experiencing strong feelings: Acevedo, "Sensory Processing Sensitivity and Neural Responses to Strangers' Emotional States." See also Jadzia Jagiellowicz, "Faster and More Intense: Emotion Processing and Attentional Mechanisms in Individuals with Sensory Processing Sensitivity."

17. In 1921, FDR contracted polio ... how suffering Americans felt: Cook, Eleanor Roosevelt, Volume One, 125236. See also The American Experience: Eleanor Roosevelt.

18. A kind woman hands a toy to a toddler ... "prosocial relationships with parents, teachers, and friends": Grazyna Kochanska et al., "Guilt in Young Children: Development, Determinants, and Relations with a Broader System of Standards," Child Development 73, no. 2 (March/April 2002): 46182. See also Grazyna Kochanska and Nazan Aksan, "Children's Conscience and Self-Regulation," Journal of Personality 74, no. 6 (2006): 15871617. See also Grazyna Kochanska et al., "Guilt and Effortful Control: Two Mechanisms That Prevent Disruptive Developmental Trajectories," Journal of Personality and Social Psychology 97, no. 2 (2009): 32233.

19. a 2010 University of Michigan study: S. H. Konrath et al., "Changes in Dispositional Empathy in American College Students Over Time: A Meta-a.n.a.lysis," Personality and Social Psychology Review, August 2010, e-publication ahead of print (accessed at http://www.ncbi.nlm.nih.gov/pubmed/20688954).

20. related to the prevalence of social media: Pamela Paul, "From Students, Less Kindness for Strangers?" New York Times, June 25, 2010.

21. when her peers were teased: Elaine Aron, The Highly Sensitive Child (New York: Random House, 2002), 18, 28283.

22. the novelist Eric Malpa.s.s: Eric Malpa.s.s, The Long Long Dances (London: Corgi, 1978).

23. High-reactive introverts sweat more: V. De Pascalis, "On the Psychophysiology of Extraversion," in On the Psychobiology of Personality: Essays in Honor of Marvin Zuckerman, edited by Marvin Zuckerman and Robert M. Stelmack (San Diego: Elsevier, 2004), 22. See also Randy J. La.r.s.en and David M. Buss, Personality Psychology: Domains of Knowledge About Human Nature (New York: McGraw-Hill, 2005),199.

24. sociopaths lie at the extreme end: Van K. Tharp et al., "Autonomic Activity During Antic.i.p.ation of an Averse Tone in Noninst.i.tutionalized Sociopaths," Psychophysiology 17, no. 2 (1980): 12328. See also Joseph Newman et al., "Validating a Distinction Between Primary and Secondary Psychopathy with Measures of Gray's BIS and BAS Constructs," Journal of Abnormal Psychology 114 (2005): 31923.

25. sociopaths have damaged amygdalae: Yaling Yang et al., "Localization of Deformations Within the Amygdala in Individuals with Psychopathy," Archives of General Psychiatry 66, no. 9 (2009), 98694.

26. Lie detectors ... are partially skin conductance tests: They also measure breathing, pulse rate, and blood pressure.

27. supercool pulse rate during liftoff: Winifred Gallagher, I.D.: How Heredity and Experience Make You Who You Are (New York: Random House, 1996), 24.

28. Corine Dijk: Corine Dijk and Peter J. De Jong, "The Remedial Value of Blushing in the Context of Transgressions and Mishaps," Emotion 9, no. 2 (2009): 28791.

29. "A blush comes online in two or three seconds": Benedict Carey, "Hold Your Head Up: A Blush Just Shows You Care," New York Times, June 2, 2009: D5.

30. "Because it is impossible to control": Ibid.

31. Keltner has tracked the roots of human embarra.s.sment ... than to mind too little: Dacher Keltner, Born to Be Good: The Science of a Meaningful Life (New York: W. W. Norton, 2009), 7496.

32. "The type that is 'sensitive' or 'reactive.' ... 'opportunity only knocks once' ": Elaine Aron, "Revisiting Jung's Concept of Innate Sensitiveness," 33767.

33. twenty-seven attributes a.s.sociated: Author interview with Elaine Aron, August 21, 2008.

34. other 30 percent are extroverts: Aron, Psychotherapy and the Highly Sensitive Person, 5.

35. More than a hundred species ... what's going on around them: Max Wolf et al., "Evolutionary Emergence of Responsive and Unresponsive Personalities," Proceedings of the National Academy of Sciences 105, no. 41 (2008): 1582530. See also Aron, Psychotherapy and the Highly Sensitive Person, 2.

36. animals had parties: David Sloan Wilson, Evolution for Everyone: How Darwin's Theory Can Change the Way We Think About Our Lives (New York: Bantam Dell, 2007), 110.

37. trade-off theory of evolution: Daniel Nettle, "The Evolution of Personality Variation in Humans and Other Animals," American Psychologist 61, no. 6 (2006): 62231.

38. When Wilson dropped metal traps: Wilson, Evolution for Everyone, 100114.

39. Trinidadian guppies: Nettle, "The Evolution of Personality Variation in Humans and Other Animals," 624. See also Shyril O'Steen et al., "Rapid Evolution of Escape Ability in Trinidadian Guppies," Evolution 56, no. 4 (2002): 77684. Note that another study found that bold fish do better with predators (but these were cichlids in fish tanks, not pike in streams): Brian R. Smith and Daniel T. Blumstein, "Behavioral Types as Predictors of Survival in Trinidadian Guppies," Behavioral Ecology 21, no. 5 (2010): 6573.

40. nomads who inherited: Dan Eisenberg et al., "Dopamine Receptor Genetic Polymorphisms and Body Composition in Undernourished Pastoralists: An Exploration of Nutrition Indices Among Nomadic and Recently Settled Ariaal Men of Northern Kenya," BMC Evolutionary Biology 8, no. 173 (2008), doi:10.1186/1471-2148-8-173. See also: http://machineslikeus.com/news/adhd-advantage-nomadic-tribesmen.

41. extroverts have more s.e.x partners ... commit more crimes. Nettle, "The Evolution of Personality Variation in Humans and Other Animals," 625. See also Daniel Nettle, Personality: What Makes You the Way You Are (New York: Oxford University Press, 2007).

42. As Jung speculated almost a century ago: Carl Jung, Psychological Types, vol. 6 of The Collected Works of C. G. Jung (Princeton, NJ: Princeton University Press, 1971), 559.

43. whose traits promote group survival: See, for example, Nicholas Wade, "The Evolution of the G.o.d Gene," New York Times, November 15, 2009.

44. "Suppose a herd of antelope": Elaine Aron, "Book Review: Unto Others: The Evolution and Psychology of Unselfish Behavior," January 2007, Comfort Zone Online: http://www.hsperson.com/pages/3Feb07.htm.

45. "hawk" and "dove" members: Elaine Aron, "A Future Headline: 'HSPs, the Key to Human Survival?' " August 2007, Comfort Zone Online: http://www.hsperson.com/pages/1Aug07.htm.

46. Great t.i.t birds: Nettle, "The Evolution of Personality Variation in Humans and Other Animals," 62425. See also Sloan Wilson, Evolution for Everyone, 110.

47. "If you send an introvert into a reception": David Remnick, "The Wilderness Campaign," The New Yorker, September 13, 2004.

48. "Most people in politics draw energy": John Heilemann, "The Comeback Kid," New York magazine, May 21, 2006.

49. "It's about the survival of the planet": Benjamin Svetkey, "Changing the Climate," Entertainment Weekly, July 14, 2006.