Moral development theorists like Piaget (Reference Piaget1932) and Kohlberg (Reference Kohlberg and Goslin1969) argued for the uniquely generative qualities of egalitarian peer relationships for the growth of moral understanding. Influenced, perhaps, by their view, Tomasello has very little to say about the relevance of parent-child interaction to the developing moral psychology of obligation. But whereas Piaget, Kohlberg, and other traditional moral development theorists contrasted peer cooperation with authority-oriented parent-child relationships, contemporary researchers have a very different view of these relationships (Thompson Reference Thompson2012). Infants learn about cooperative social interaction in the contexts of social play, feeding, and other shared activities of joint intentionality within the family. They expect parents to act consistently with their roles, and protest when parents fail to do so (e.g., Adamson & Frick Reference Adamson and Frick2003). A developing morality of obligation derives, in part, from the mutual responsiveness of parents and children in relationships of reciprocal cooperation.

It would be reasonable to expect that humans’ ultra-cooperative nature would be manifested in early parent-child interaction, especially because human infants are born more dependent on the cooperative solicitude of their caregivers than are other great apes. The species-typical preference of humans for pursuing goals collaboratively cannot be viewed independently of the conditions required for the survival of human young. Infants’ helplessness contributes to the creation of the “social cradle” (Carpendale et al. Reference Carpendale, Hammond, Atwood, Lerner and Benson2013) of cooperative social interactions that contribute to their survival, especially in the context of alloparenting that is likely to have characterized infant care (Hrdy Reference Hrdy2009). But the social cradle is also likely to have made infants exquisitely attuned to the cooperative responses they receive and observe in those around them because cooperative encounters sensitize a helpless infant to whom they could trust to provide reliable support. Understanding from whom cooperative solicitude would be received and, by extension, who could be observed cooperating with others is likely to have enabled infants to direct their bids for support to appropriate adults (Chisholm, Reference Chisholm, Thompson, Simpson and Berlinin press).

This early developing attunement to cooperative relations likely underlies the differential responses of young infants to observed “helpers” and “hinderers” argued by Hamlin (Reference Hamlin2013) to be a predicate to a moral sense. It is also a foundation to secure or insecure attachment. Infants’ sensitivity to cooperative relations changes, of course, with psychological development. We have argued, for example, that as toddlers acquire an awareness of shared intentionality during the second year, they begin to understand parental sensitivity as the adult sharing the toddler's goals in the situation, and they may extend this orientation to third parties (Newton et al. Reference Newton, Thompson and Goodman2016). This is, in Tomasello's terms, the shared “we” in parent-child interaction extended to another.

Another developmental transition in parent-child relationships occurs when young children become capable of – and are motivated to – reciprocate the cooperation they receive. Maccoby (Reference Maccoby1984) and more recently Kochanska (Reference Kochanska2002) have argued that parental socialization during this period is a process of inducting the child into a system of reciprocity, manifested in the formation of a jointly binding, reciprocal, and mutually responsive relationship. In this relationship, young children are motivated to cooperate with parental requests and incentives not because of threat or coercion but owing to the reciprocal obligations that close relationships entail and to maintain relational harmony. Considerable research in the study of conscience development has tested this view and shown, in several longitudinal samples, that when early parent-child relationships were characterized by this “mutually responsive orientation” children subsequently showed greater cooperativeness in parent-child interaction, exhibited greater compliance in the parent's absence, offered greater prosocial completions to incomplete stories, and showed a stronger sense of self as a moral actor (see Kochanska et al. Reference Kochanska, Boldt and Goffin2019). In Kochanska's view, early parent-child relational experience characterized by shared reciprocity, including felt mutual obligation, launches young children on a developmental pathway that includes greater cooperative conduct and responsiveness to shared responsibilities outside the family.

Early attunement to cooperative relations manifests also in young children's development of secure attachment in the context of sensitive care. Just as a mutually responsive orientation is not guaranteed in early parent-child relationships, so also parental sensitivity is not necessarily ensured in any infant's experience. Thus distinguishing which parental (and other alloparental) partners could be counted on for cooperative support is important for the security felt within those relationships and also to the developing readiness to seek and establish similar relationships of shared agency with others. This may be one reason why the security of attachment is longitudinally associated with many elements of cooperative obligation that Tomasello discusses, such as cooperation with adults and peers, social problem-solving and conflict-avoidance with peers, as well as fidelity to social norms and fairness sensitivity in conscience development (Thompson Reference Thompson, Laible, Padilla-Walker and Carlo2019). Although individual differences in the readiness to established shared agency with another are not a focus of Tomasello's analysis, individual differences in the human sense of obligation warrants systematic study. Interestingly, in an essay written at the conclusion of World War II and thus two decades before the publication of Attachment, Bowlby (Reference Bowlby1946) discussed research documenting the feeling of “We'ness” evoked by children's participation in democratically structured groups, by contrast with the feeling of “I'ness” evoked by participation in autocratically directed groups. His essay urged governments to devote attention to the developmental conditions giving rise to human cooperation and conflict management.

Taken together, the young children studied in the evocative studies described by Tomasello do not arrive at cooperative interactions of joint intentionality with peers and adults de novo. Their capacities for establishing the “we'ness” of collaborative activity, mutual obligation, and in-group solidarity are also established in the attunement to cooperative relations and the mutual obligations of relationships in the family. Tomasello's moral psychology of obligation would be developmentally deepened by consideration of a young child's long experience of parent-child interactions that provide foundations to a developing sense of social obligation that precede and are concurrent with the developmental processes he so evocatively discusses. The unique achievements arising from the egalitarian context of peer relationships build on those occurring in the family.