This longitudinal study (N = 204) examines if the association between maternal cooperative values or personality and 14-month-olds’ cooperative ability with an adult experimenter across two tasks is mediated by infant temperament (i.e., biology) or infants’ early at-home cooperative experience through social gameplay at the age of 9 months (i.e., socialisation). The results revealed that infants of mothers with other-oriented cooperative values demonstrated increased coordination and success on the cooperative task requiring complementary actions. Infants of mothers high in cooperative personality traits agreeableness and honesty-humility demonstrated increased coordination and success on the cooperative task involving parallel actions. Neither infant temperament nor the frequency of social gameplay mediated these effects. These findings offer the first evidence suggesting that 14-month-old infants’ cooperative ability is shaped by their parents’ cooperative dispositions.

Interaction quality during cooperative exchanges impacts children’s ability to successfully coordinate their actions with a same-aged peer to attain a shared goal. However, it is unclear how first impressions formed in one context shape children’s ability to cooperate in a subsequent task. In the present research, we examine whether the interaction quality (e.g., affiliation, antagonism, joint coordinated engagement, and joint contribution) of a warm-up period between two-year-old unfamiliar dyads (N = 144 dyads) predicts the dyad’s performance and interaction quality in a following cooperative task. Children who participated more effectively during a toy clean-up activity at the end of the warm-up interaction were more likely to respond to their partner’s efforts to cooperate in the novel cooperative task. Initial displays of affiliation during the warm-up period appeared to enhance cooperative ability by facilitating cooperative motivation. The present research demonstrates that first impressions influence toddlers’ cooperative performance and thus, highlights the importance of considering task order and children’s social behaviours when designing studies on cooperative competence.