Breastfeeding exposure and developmental lateralization: circuit-specific associations with handedness and...

Hemispheric specialization is increasingly conceptualized as a multidimensional system of partially independent functional circuits. Developmental models propose that early caregiving experiences contribute to the probabilistic stabilization of asymmetries through repeated multisensory interactions. Breastfeeding represents one such early caregiving context involving repeated multisensory caregiver-infant interactions. This study examined associations between breastfeeding exposure and behavioral indices of hemispheric asymmetry in young adults across motor (finger tapping), spatial (line bisection), perceptual (Navon), and interhemispheric transfer (Poffenberger) domains. Regression models tested whether breastfeeding ≥6 months predicted asymmetry while controlling for sex, gestational age, and birth weight. In this sample of 90 young adults, breastfeeding ≥6 months was associated with stronger rightward motor asymmetry (b = 0.055, β = 0.25, 95% CI [0.019, 0.090], p = .003) and spatial attention bias (b = 1.162, β = 0.33, 95% CI [0.300, 2.025], p = .009), with no associations for Navon (p = .728) or Poffenberger (p = .432). These findings are consistent with a circuit-specific developmental model of lateralization in which early caregiving experiences may contribute to the stabilization of selected lateralized systems.