Placebo

A medically or chemically inert substance or procedure that a person (usually participant or the researchers) believes will help them or make them recover. Placebos are used in scientific research to determine the effectiveness of the drug or treatment.

Reference:
Florian, V., Mikulincer, M., & Hirschberger, G. (1999). The anatomy of a problematic emotion—the conceptualization and measurement of the experience of pity. Imagination, Cognition and Personality, 19(1), 3-25. doi: 10.2190/4JG9-M79P-HJYK-AQNE.

Weiner, B., Graham, S., & Chandler, C. (1982). Pity, Anger, and Guilt: An Attributional Analysis. Personality and Social Psychology Bulletin, 8(2), 226-232. doi: 10.1177/0146167282082007.

Goetz, J. L., Keltner, D., & Simon-Thomas, E. (2010). Compassion: an evolutionary analysis and empirical review. Psychological Bulletin, 136(3), 351-374. doi: 0.1037/a0018807.