Social connectedness without eye contact: 18- but not 9-month-olds use proximal touch to infer third-party joint attention during observational learning.

Decades of research have highlighted the important role of joint attention in early cultural learning. However, most previous studies focused on a limited range of joint attention settings involving the learner's first-person participation in joint visual attention, characterized by eye contact and triadic gaze following. This has created an incomplete picture, tending to neglect the diversity in which infants experience social connectedness in their daily lives. To deepen our understanding of the multifaceted nature of joint attention, this study investigated infants' object memory in previously unexplored joint attention contexts, including physical cues of togetherness within observed interactions. Nine- and 18-month-old German infants participated in an object encoding task featuring videos of two people looking at an object. The videos varied in the presence and combination of mutual eye contact and mutual touch in physical proximity. After each video, the familiarized object reappeared next to a novel object. Infants' looking time preference for the novel object was used as a measure of their prior encoding of the familiarized object. Eighteen-month-olds demonstrated superior encoding in all conditions involving interpersonal connectedness, expressed through eye contact, proximal touch, or a combination of both. In contrast, 9-month-olds' object encoding was only enhanced in the presence of eye contact, regardless of proximal touch. These findings demonstrate a developmental refinement from a primary reliance on visual cues to a more comprehensive understanding of third-party jointness incorporating a broader range of cues. Joint attention is a highly flexible social learning mechanism, capable of operating in diverse social environments. (PsycInfo Database Record (c) 2025 APA, all rights reserved).