J. Andreoni, Impure altruism and donations to public goods: A theory of warmglow giving, Economic Journal, vol.100, pp.464-477, 1990.

D. Ariely, A. Bracha, and S. Meier, Doing good or doing well? Image motivation and monetary incentives in behaving prosocially, American Economic Review, vol.99, pp.544-55, 2009.

S. E. Asch, E¤ects of group pressure upon the modi?cation and distortion of judgments, Documents of Gestalt Psychology, pp.222-236, 1951.

S. E. Asch, Opinions and social pressure, Scienti?c American, vol.193, pp.31-35, 1955.

F. Banque-de, An Overview of Philanthropy in Europe, 2015.

S. Barrett and A. Dannenberg, An experimental investigation into 'pledge and review'in climate negotiations, Climatic Change, vol.138, pp.1-2, 2016.

P. Battigalli and M. Dufwenberg, Guilt in games, American Economic Review, vol.97, pp.170-176, 2007.

C. Bazin, M. Ducros, and J. Malet, La Générosité des Français 2017, 22eme édition, Editions Recherches et Solidarités, 2017.

R. Bénabou and J. Tirole, Incentives and prosocial behavior, American Economic Review, vol.96, pp.1652-1678, 2006.

B. Bernheim and . Douglas, A theory of conformity, Journal of Political Economy, vol.102, pp.841-877, 1994.

C. Gary and M. Dufwemberg, Promises and partnership, Econometrica, vol.74, pp.1579-1601, 2006.

S. Cotterill, P. John, and L. Richardson, The impact of a pledge request and the promise of publicity: A randomized controlled trial of charitable donations, Social Science Quarterly, vol.94, pp.200-216, 2013.

V. P. Crawford and J. Sobel, Strategic information transmission, Econometrica, pp.1431-1451, 1982.

M. Damgaard, C. Trier, and . Gravert, Now or never! The e¤ect of deadlines on charitable giving: Evidence from two natural ?eld experiments, Journal of Behavioral and Experimental Economics, vol.66, pp.78-87, 2017.

. Dellavigna, J. A. Stefano, U. List, and . Malmendier, Testing for altruism and social pressure in charitable giving, Quarterly Journal of Economics, vol.127, pp.1-56, 2012.

D. Wit, A. , and R. Bekkers, Government support and charitable donations: A meta-analysis of the crowding-out hypothesis, Journal of Public Administration Research and Theory, vol.27, pp.301-319, 2017.

J. M. Feldman and J. G. Lynch, Self-generated validity and other e¤ects of measurement on belief, attitude, intention, and behavior, Journal of Applied Psychology, vol.73, p.421, 1988.

G. Gawn and R. Innes, Language and lies, Journal of Behavioral and Experimental Economics, vol.74, pp.167-176, 2018.

U. Giving, Giving USA 2017: The Annual Report on Philanthropy for the Year, 2016.

A. Glazer and K. A. Konrad, A signaling explanation for charity, American Economic Review, vol.86, pp.1019-1028, 1996.

U. Gneezy, Deception: The role of consequences, American Economic Review, vol.95, pp.384-394, 2005.

P. M. Gollwitzer and P. Sheeran, Implementation intentions and goal achievement: A meta-analysis of e¤ects and processes, Advances in Experimental Social Psychology, vol.38, pp.69-119, 2006.

Z. Grossman, Self-signaling and social-signaling in giving, Journal of Economic Behavior and Organization, vol.117, pp.26-39, 2015.

A. Koessler, Setting new behavioural standards: Sustainabilty pledges and how conformity impacts their outreach, Working Paper ZBW, 2019.

J. A. List, The market for charitable giving, Journal of Economic Perspectives, vol.25, pp.157-80, 2011.

R. Martin and J. Randal, How is donation behaviour a¤ected by the donations of others, Journal of Economic Behavior and Organization, vol.67, pp.228-238, 2008.

N. Mazar, O. Amir, and D. Ariely, The dishonesty of honest people: A theory of self-concept maintenance, Journal of Marketing Research, vol.45, pp.633-644, 2008.

T. Meyvis, A. Bennett, and D. M. Oppenheimer, Precommitement to charity, The Science of Giving: Experimental Approaches to the Study of Charity, 2011.

V. G. Morwitz, E. Johnson, and D. Schmittlein, Does measuring intent change behavior, Journal of Consumer Research, vol.20, pp.46-61, 1993.

E. C. Nook, C. Desmond, S. A. Ong, J. P. Morelli, J. Mitchell et al., Prosocial conformity: Prosocial norms generalize across behavior and empathy, Personality and Social Psychology Bulletin, vol.42, pp.1045-1062, 2016.

J. L. Peifer, The economics and sociology of religious giving: Instrumental rationality or communal bonding?, Social Forces, vol.88, pp.1569-1594, 2010.

D. Prelec and G. Loewenstein, The red and the black: Mental accounting of savings and debt, Marketing Science, vol.17, pp.4-28, 1998.

K. Scharf, Impure prosocial motivation in charity provision: Warm-glow charities and implications for public funding, Journal of Public Economics, vol.114, pp.50-57, 2014.

J. F. Schulz, P. Thiemann, and C. Thöni, Nudging generosity: Choice architecture and cognitive factors in charitable giving, Journal of Behavioral and Experimental Economics, vol.74, pp.139-145, 2018.

S. Schwartz, E. Spires, and R. Young, Why do people keep their promises? A further investigation, Experimental Economics, 2018.

J. Shang and R. Et-croson, A ?eld experiment in charitable contribution: The impact of social information on the voluntary provision of public goods, Economic Journal, vol.119, pp.1422-1439, 2009.

S. Smith, F. Windmeijer, and E. Wright, Peer e¤ects in charitable giving: Evidence from the (running) ?eld, Economic Journal, vol.125, pp.1053-1071, 2015.

, Your pair made a gift of

, Your guess about the partner's gift was

, The total gain is