Socioeconomic status affects oral and manual exploration across the first year

Oral and manual exploration are part of the foundation of problem solving and cognition in infancy. How these develop in an at-risk population, infants in poverty, is unknown. The current study tested exploratory behaviors longitudinally at 6, 9, and 12 months in infants from high- and low-socioeconomic (SES) families. Oral exploration consisted of passive and active mouthing and looks after active mouthing. Manual exploration consisted of frequency of fingering, rotating, and transferring the object. High-SES infants replicated the trajectory previously reported in the literature, showing a decrease in mouthing and fingering and an increase in rotating and transferring (e.g., Palmer, 1989). In contrast, low-SES infants showed no change in any of the manual exploratory behaviors over the first year, thus demonstrating reduced overall levels of exploration as well as a different developmental trajectory. Results are discussed in terms of attention, potential physiological mechanisms, and implications for later problem solving.