Table 1.

Criteria for intentionality in marmoset prosociality

Criteria and Markers	Evidence
FLEXIBILITY (INSTRUMENTAL GOALS)
Behavioral adjustment  to specific conditions	Naturalistic behavior in wild and captivity: more proactive food sharing when food is novel or difficult to obtain for immatures1–7
Means-end dissociation
i.e. to be able to use multiple means to achieve a goal	Dyadic game and group service: proactive prosociality not only expressed in proactive food sharing under naturalistic conditions, but also in experimental contexts requiring novel actions8,9
AUDIENCE EFFECTS
Audience effects I  i.e. to only show the behavior when an audience (recipient) or a specific audience (composition) is present	Naturalistic context: more food calls when others are out of sight but within earshot, to inform them about the presence of food10,11 (recipient) or when immatures are in the group (composition)12–14
	Experimental contexts: more pulling when partner(s) is present than when absent in dyadic games8 and group service (this study)
Audience effects II
i.e. whether the presence of additional potential helpers influences helping	Experimental context: more proactive sharing with immatures when it alone is responsible for them15
GOAL-DIRECTEDNESS (SOCIAL GOALS)
Persistence  i.e. behavior continues until putative goal (response) is reached	Experimental group service context: the behavior “holding the tray” continues exactly until the goal (taking the food by recipient) is reached (this study)
Audience checking  i.e. show a distinct reaction when the behavior does not result in the putative goal	Experimental Dyadic games: prosocial individuals check back and look at/for their partner when they have pulled food to within reach for them but the partner does not retrieve the food (this study)

Entries refer to published evidence showing how these criteria are met by marmoset prosociality in naturalistic and experimental contexts; entries in bold italics refer to evidence presented in this study

¹Guerreiro Martins and Burkart (2013)

²Humle and Snowdon (2008)

³Moura et al. (2010)

⁴Price and Feistner (1993)

⁵Rapaport (2011)

⁶Yamamoto et al. (2014)

⁷Rapaport (1999)

⁸Burkart et al. (2007)

⁹Burkart et al. (2014)

¹⁰Vitale et al. (2003)

¹¹Caine et al. (1995)

¹²Feistner and Price (1991)

¹³Joyce and Snowdon (2003)

¹⁴Rapaport (2011)

¹⁵Brügger et al. (2018)