Isen, A. M., &Levin, P. F. (1972). Effect of feeling good on helping: Cookies and kindness. Journal of Personality and Social Psychology, 21(3), 384-388.
Investigated the effects of a person's positive affective state on his or her subsequent helpfulness to others. "Feeling good" was induced (a) in 52 male undergraduates by having received cookies while studying in a library (Study I), and (b) in 24 female and 17 male adults by having found a dime in the coin return of a public telephone (Study II). In Study I, where ...