Final answer:
The main features of infants' social worlds across cultures include language development, social interactions, and self-awareness.
Step-by-step explanation:
The main features of infants' social worlds across cultures include language development, social interactions, and self-awareness. In all cultures, infants learn to be proficient in their languages through different forms of interaction between caregiver and baby. Language ideologies, which are specific ideas about language acquisition and variation, vary across cultures. Infants in all cultures reach language milestones in a similar sequence, but cultural differences in child care practices can affect other developmental milestones. Additionally, infants develop a positive sense of self through self-awareness, which typically develops around 18 months of age. Infants' sensory abilities and preferences also play a role in their social worlds, such as their preference for faces and human voices.