Score contribution per author:
α: calibrated so average coauthorship-adjusted count equals average raw count
Kindness is an important concept in reciprocity theory, and may matter also for other forms of motivation. We critically compare definitions proposed by Rabin (1993) and by Dufwenberg and Kirchsteiger (2004). Several reasons to prefer the latter definition are highlighted, but also a flaw (discovered by Isoni and Sugden 2018) which we show can be eliminated using a slightly revised definition.