Developmental Trajectories of Joint Attention and Behavioral Request in Infancy: A Longitudinal Study from 8 to 18 Months

Background/Objectives: Joint attention and behavioral request are foundational component of early social communication and play a crucial role in later socio-cognitive development. This study aimed to examine the developmental trajectories of joint attention and behavioral request behaviors across infancy. Methods: A longitudinal design was employed with a birth cohort of 55 infants from Valencia, Spain, assessed at 8, 12, and 18 months of age. Joint attention and behavioral request behaviors were evaluated using the Early Social Communication Scales (ESCS). Linear mixed-effects models (LMMs) were fitted to examine developmental changes over time. Results: The findings revealed differentiated developmental trajectories depending on the level of behavioral complexity. Low-level Initiating Joint Attention remained stable across time, whereas high-level Initiating and Responding to Joint Attention behaviors increased significantly with age. Similarly, behavioral request behaviors showed a shift from early low-level forms to more complex and intentional behaviors over time. Significant developmental changes were observed for both joint attention and behavioral request across ages. Conclusions: Joint attention and behavioral request follow a hierarchical developmental pattern during infancy, characterized by early stability in basic behaviors and later emergence of more complex communicative forms. These findings contribute to a better understanding of typical development and highlight the relevance of early social communication behaviors as potential markers of developmental risk.