1. Beecher, H. K. The powerful placebo. J. Am. Med. Assoc. 159, 1602–1606 (1955).

2. Gold, H., Kwit, N. T. & Otto, H. The xanthines (theobromine and aminophylline) in the treatment of cardiac pain. J. Am. Med. Assoc. 108, 2173–2179 (1937).

3. Rosenzweig, S. Some implicit common factors in diverse methods of psychotherapy. Am. J. Orthopsychiatry 6, 412–415 (1936).

4. Houston, W. R. The doctor himself as a therapeutic agent. Ann. Intern. Med. 11, 1416 (1938).

5. Uhlenhuth, E. H., Canter, A., Neustadt, J. O. & Payson, H. E. The symptomatic relief of anxiety with meprobamate, phenobarbital and placebo. Am. J. Psychiatry 115, 905–910 (1959).

6. Shapiro, A. K. & Shapiro, E. The Powerful Placebo: From Ancient Priest to Modern Physician (JHU Press, 2000).

7. Ioannidis, J. P. et al. Comparison of evidence of treatment effects in randomized and nonrandomized studies. J. Am. Med. Assoc. 286, 821–830 (2001).

8. Świder, K. & Bąbel, P. The effect of the sex of a model on nocebo hyperalgesia induced by social observational learning. Pain 154, 1312–1317 (2013).

9. Vögtle, E., Barke, A. & Kröner-Herwig, B. Nocebo hyperalgesia induced by social observational learning. Pain 154, 1427–1433 (2013).

10. Colloca, L. & Benedetti, F. Placebo analgesia induced by social observational learning. Pain 144, 28–34 (2009).

11. Koban, L. & Wager, T. D. Beyond conformity: social influences on pain reports and physiology. Emotion 16, 24–32 (2016).

12. Yoshida, W., Seymour, B., Koltzenburg, M. & Dolan, R. J. Uncertainty increases pain: evidence for a novel mechanism of pain modulation involving the periaqueductal gray. J. Neurosci. 33, 5638–5646 (2013).

13. Haaker, J., Yi, J., Petrovic, P. & Olsson, A. Endogenous opioids regulate social threat learning in humans. Nat. Commun. 8, 15495 (2017).

14. Benedetti, F., Durando, J. & Vighetti, S. Nocebo and placebo modulation of hypobaric hypoxia headache involves the cyclooxygenase-prostaglandins pathway. Pain 155, 921–928 (2014).

15. Holtzheimer, P. E. et al. Subcallosal cingulate deep brain stimulation for treatment-resistant depression: a multisite, randomised, sham-controlled trial. Lancet Psychiatry 4, 839–849 (2017).

16. Ashar, Y. K., Chang, L. J. & Wager, T. D. Brain mechanisms of the placebo effect: an affective appraisal account. Annu. Rev. Clin. Psychol. 13, 73–98 (2017).

17. Price, D. D., Finniss, D. G. & Benedetti, F. A comprehensive review of the placebo effect: recent advances and current thought. Annu. Rev. Psychol. 59, 565–590 (2008).

18. Benedetti, F., Mayberg, H. S., Wager, T. D., Stohler, C. S. & Zubieta, J.-K. Neurobiological mechanisms of the placebo effect. J. Neurosci. 25, 10390–10402 (2005).

19. Benedetti, F. The Patient’s Brain: The Neuroscience Behind the Doctor–Patient Relationship (Oxford Univ. Press, 2011).

20. Geuter, S., Koban, L. & Wager, T. D. The cognitive neuroscience of placebo effects: concepts, predictions, and physiology. Annu. Rev. Neurosci. 40, 167–188 (2017).

21. de la Fuente-Fernández, R. et al. Expectation and dopamine release: mechanism of the placebo effect in Parkinson’s disease. Science 293, 1164–1166 (2001).

22. Jensen, K. B. et al. Sharing pain and relief: neural correlates of physicians during treatment of patients. Mol. Psychiatry 19, 392–398 (2014).

23. Olanow, C. W. et al. Gene delivery of neurturin to putamen and substantia nigra in Parkinson disease: a double-blind, randomized, controlled trial. Ann. Neurol. 78, 248–257 (2015).

24. Luborsky, L. et al. The researcher’s own therapy allegiances: a ‘wild card’ in comparisons of treatment efficacy. Clin. Psychol. Sci. Pract. 6, 95–106 (1999).

25. Walach, H., Sadaghiani, C., Dehm, C. & Bierman, D. The therapeutic effect of clinical trials: understanding placebo response rates in clinical trials—a secondary analysis. BMC Med. Res. Methodol. 5, 26–37 (2005).

26. Greenberg, R. P., Bornstein, R. F., Zborowski, M. J., Fisher, S. & Greenberg, M. D. A meta-analysis of fluoxetine outcome in the treatment of depression. J. Nerv. Ment. Dis. 182, 547–551 (1994).

27. Holroyd, K. A., Tkachuk, G., O’Donnell, F. & Cordingley, G. E. Blindness and bias in a trial of antidepressant medication for chronic tension-type headache. Cephalalgia 26, 973–982 (2006).

28. Margraf, J. et al. How ‘blind’ are double-blind studies? J. Consult. Clin. Psychol. 59, 184–187 (1991).

29. Morin, C. M. et al. How blind are double-blind placebo-controlled trials of benzodiazepine hypnotics. Sleep 18, 240–245 (1995).

30. Miller, F. G., Colloca, L. & Kaptchuk, T. J. The placebo effect: illness and interpersonal healing. Perspect. Biol. Med. 52, 518–539 (2009).

31. Blasini, M., Peiris, N., Wright, T. & Colloca, L. The role of patient–practitioner relationships in placebo and nocebo phenomena. Int. Rev. Neurobiol. 139, 211–231 (2018).

32. Rosenthal, R. & Rubin, D. B. Interpersonal expectancy effects: the first 345 studies. Behav. Brain Sci. 1, 377–386 (1978).

33. Rosenthal, R. Interpersonal expectancy effects: a 30-year perspective. Curr. Dir. Psychol. Sci. 3, 176–179 (1994).

34. Pfungst, O. Clever Hans:(The Horse of Mr. Von Osten.) A Contribution to Experimental Animal and Human Psychology (Holt, Rinehart and Winston, 1911).

35. Rosenthal, R. & Lawson, R. A longitudinal study of the effects of experimenter bias on the operant learning of laboratory rats. J. Psychiatr. Res. 2, 61–72 (1964).

36. Rosenthal, R. & Jacobson, L. Pygmalion in the classroom. Urban Rev. 3, 16–20 (1968).

37. Rosenthal, R. Experimenter Effects in Behavioral Research (Appleton–Century–Crofts, 1966).

38. Doyen, S., Klein, O., Pichon, C.-L. & Cleeremans, A. Behavioral priming: it’s all in the mind but whose mind? PLoS One 7, e29081 (2012).

39. Joyce, A. S. & Piper, W. E. Expectancy, the therapeutic alliance, and treatment outcome in short-term individual psychotherapy. J. Psychother. Pract. Res. 7, 236–248 (1998).

40. Meyer, B. et al. Treatment expectancies, patient alliance and outcome: further analyses from the national institute of mental health treatment of depression collaborative research program. J. Consult. Clin. Psychol. 70, 1051–1055 (2002).

41. Arnkoff, D. B., Glass, C. R. & Shapiro, S. J. in Psychotherapy Relationships that Work: Therapist Contributions and Responsiveness to Patients (ed. Norcross, J. D.) 325–346 (Oxford Univ. Press, 2002).

42. Gracely, R. H., Dubner, R., Deeter, W. R. & Wolskee, P. J. Clinicians expectations influence placebo analgesia. Lancet 1, 43–43 (1985).

43. Schafer, S. M., Colloca, L. & Wager, T. D. Conditioned placebo analgesia persists when subjects know they are receiving a placebo. J. Pain 16, 412–420 (2015).

44. Voudouris, N. J., Peck, C. L. & Coleman, G. The role of conditioning and verbal expectancy in the placebo response. Pain 43, 121–128 (1990).

45. Orne, M. T. On the social psychology of the psychological experiment: with particular reference to demand characteristics and their implications. Am. Psychol. 17, 776 (1962).

46. Cheong, J., Brooks, S. & Chang, L. J. “FaceSync: Open Source Framework for Recording Facial Expressions with Head-Mounted Cameras.” F1000Res. 8, 702 (2019).

47. Littlewort, G. et al. The computer expression recognition toolbox (CERT). Face Gesture 2011, 298–305 (2011).

48. iMotions Biometric Research Platform v.6.0 (iMotions A/S, 2016).

49. Ekman, P. & Friesen, W. V. Measuring facial movement. J. Nonverbal Behav. 1, 56–75 (1976).

50. Prkachin, K. M. The consistency of facial expressions of pain: a comparison across modalities. Pain 51, 297–306 (1992).

51. Lucey, P. et al. Automatically detecting pain in video through facial action units. IEEE Trans. Syst. Man Cybern. B 41, 664–674 (2011).

52. Walach, H., Schimdt, S., Bihr, Y.-M. & Wiesch, S. The effects of a caffeine placebo and experimenter expectation on blood pressure, heart rate, well-being, and cognitive performance. Eur. Psychol. 6, 15 (2001).

53. Walach, H., Schmidt, S., Dirhold, T. & Nosch, S. The effects of a caffeine placebo and suggestion on blood pressure, heart rate, well-being and cognitive performance. Int. J. Psychophysiol. 43, 247–260 (2002).

54. Halverson, A. M., Hallahan, M., Hart, A. J. & Rosenthal, R. Reducing the biasing effects of judges’ nonverbal behavior with simplified jury instruction. J. Appl. Psychol. 82, 590 (1997).

55. Learman, L. A., Avorn, J., Everitt, D. E. & Rosenthal, R. Pygmalion in the nursing home. The effects of caregiver expectations on patient outcomes. J. Am. Geriatr. Soc. 38, 797–803 (1990).

56. Wu, L. M., Mohamed, N. E., Winkel, G. & Diefenbach, M. A. Patient and spouse illness beliefs and quality of life in prostate cancer patients. Psychol. Health 28, 355–368 (2013).

57. Wampold, B. E., Mondin, G. W., Moody, M. & Stich, F. A meta-analysis of outcome studies comparing bona fide psychotherapies: empiricially, ‘all must have prizes’. Psychol. Bull. 122, 203–215 (1997).

58. Wampold, B. E. & Imel, Z. E. The Great Psychotherapy Debate: The Evidence for What Makes Psychotherapy Work (Routledge, 2015).

59. Weinberger, J. Common factors aren’t so common: the common factors dilemma. Clin. Psychol. Sci. Pract. 2, 45–69 (1995).

60. Frank, J. D. & Frank, J. B. Persuasion and Healing: A Comparative Study of Psychotherapy (JHU Press, 1993).

61. Rogers, C. R. The necessary and sufficient conditions of therapeutic personality change. J. Consult. Psychol. 21, 95–103 (1957).

62. Yahne, C. E. & Miller, W. R. in Integrating Spirituality into Treatment: Resources for Practitioners (ed. Miller, W. R.) 217–233 (American Psychological Association, 1999).

63. Ackerman, S. J. & Hilsenroth, M. J. A review of therapist characteristics and techniques positively impacting the therapeutic alliance. Clin. Psychol. Rev. 23, 1–33 (2003).

64. Lester, G. W. & Smith, S. G. Listening and talking to patients. A remedy for malpractice suits? West. J. Med. 158, 268–272 (1993).

65. Luborsky, L., McLellan, A. T., Woody, G. E., O’Brien, C. P. & Auerbach, A. Therapist success and its determinants. Arch. Gen. Psychiatry 42, 602–611 (1985).

66. Okiishi, J., Lambert, M. J., Nielsen, S. L. & Ogles, B. M. Waiting for supershrink: an empirical analysis of therapist effects. Clin. Psychol. Psychother. 10, 361–373 (2003).

67. Wampold, B. E. & Brown, G. S. J. Estimating variability in outcomes attributable to therapists: a naturalistic study of outcomes in managed care. J. Consult. Clin. Psychol. 73, 914–923 (2005).

68. Martin, D. J., Garske, J. P. & Davis, M. K. Relation of the therapeutic alliance with outcome and other variables: a meta-analytic review. J. Consult. Clin. Psychol. 68, 438–450 (2000).

69. Derksen, F., Bensing, J. & Lagro-Janssen, A. Effectiveness of empathy in general practice: a systematic review. Br. J. Gen. Pract. 63, e76–84 (2013).

70. Horvath, A. & Luborsky, L. The role of the therapeutic alliance in psychotherapy. J. Consult. Clin. Psychol. 61, 561–573 (1993).

71. Horvath, A. & Symonds, B. D. Relation between working alliance and outcome in psychotherapy: a meta-analysis. J. Couns. Psychol. 38, 139 (1991).

72. Rakel, D. et al. Perception of empathy in the therapeutic encounter: effects on the common cold. Patient Educ. Couns. 85, 390–397 (2011).

73. Necka, E. A. & Atlas, L. Y. The role of social and interpersonal factors in placebo analgesia. Int. Rev. Neurobiol. 138, 161–179 (2018).

74. Thurstone, L. L. A law of comparative judgment. Psychol. Rev. 34, 273–286 (1927).

75. Fechner, G. T. Elemente der Psychophysik (Breitkopf and Hartel,1860).

76. Kahneman, D. & Tversky, A. Prospect theory: an analysis of decision under risk. Econometrica 47, 263–291 (1979).

77. Flaten, M. A., Aslaksen, P. M., Lyby, P. S. & Bjørkedal, E. The relation of emotions to placebo responses. Phil. Trans. R. Soc. Lond. B 366, 1818–1827 (2011).

78. Lyby, P. S., Aslaksen, P. M. & Flaten, M. A. Is fear of pain related to placebo analgesia? J. Psychosom. Res. 68, 369–377 (2010).

79. Wager, T. D. & Atlas, L. Y. The neuroscience of placebo effects: connecting context, learning and health. Nat. Rev. Neurosci. 16, 403–418 (2015).

80. Batt-Rawden, S. A., Chisolm, M. S., Anton, B. & Flickinger, T. E. Teaching empathy to medical students: an updated, systematic review. Acad. Med. 88, 1171–1177 (2013).

81. Sulzer, S. H., Feinstein, N. W. & Wendland, C. L. Assessing empathy development in medical education: a systematic review. Med. Educ. 50, 300–310 (2016).

82. Fine, V. K. & Therrien, M. E. Empathy in the doctor–patient relationship: skill training for medical students. J. Med. Educ. 52, 752–757 (1977).

83. Ha, J. F. & Longnecker, N. Doctor–patient communication: a review. Ochsner J. 10, 38–43 (2010).

84. Vandewauw, I. et al. A TRP channel trio mediates acute noxious heat sensing. Nature 555, 662–666 (2018).

85. Jepma, M., Jones, M. & Wager, T. D. The dynamics of pain: evidence for simultaneous site-specific habituation and site-nonspecific sensitization in thermal pain. J. Pain 15, 734–746 (2014).

86. Davis, M. H. Measuring individual differences in empathy: evidence for a multidimensional approach. J. Pers. Soc. Psychol. 44, 113–126 (1983).

87. McKinney, W. Data structures for statistical computing in Python. Proc. 9th Python Sci. Conf. 445, 51–56 (2010).

88. Oliphant, T. E. A Guide to NumPy, vol. 1 (Trelgol, 2006).

89. Waskom, M. et al. Seaborn: Statistical Data Visualization (accessed on 15 May 2017); https://seaborn.pydata.org/

90. Hunter, J. D. Matplotlib: a 2D graphics environment. Comput. Sci. Eng. 9, 90–95 (2007).

91. Pedregosa, F. et al. Scikit-learn: machine learning in python. J. Mach. Learn. Res. 12, 2825–2830 (2011).

92. Oliphant, T. E. Python for scientific computing. Comput. Sci. Eng. 9, 10–20 (2007).

93. Millman, K. J. & Aivazis, M. Python for scientists and engineers. Comput. Sci. Eng. 13, 9–12 (2011).

95. Bates, D., Mächler, M., Bolker, B. & Walker, S. Fitting linear mixed-effects models using lme4. J. Stat. Softw. https://www.jstatsoft.org/article/view/v067i01 (2015).

96. Kuznetsova, A., Brockhoff, P. B. & Christensen, R. H. B. lmerTest: Tests for random and fixed effects for linear mixed effect models. R package version 2.0-11 http://CRAN.R-project.org/package=lmerTest (2014).

97. Lenth, R. V. Least-squares means: the R Package lsmeans. J. Stat. Softw. 69, 1–33 (2016).

98. Jolly, E. Pymer4: connecting R and Python for linear mixed modeling. J. Open Source Softw. 3, 862 (2018).

99. Werner, P. et al. Automatic pain assessment with facial activity descriptors. IEEE Trans. Affect. Comput. 8, 286–99 (2017).

100. Lucey, P. et al. in IEEE Computer Society Conference on Computer Vision and Pattern Recognition Workshops 94–101 (IEEE, 2010).