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Throughout our development, we form lateralized biases (Goodwin & Michel, 1981), from selecting an object with one hand to complex role-differentiated bimanual actions. Handedness is an easily observable lateralized behavior and involves the consistent use of one hand when performing manual tasks. These manual actions concern the motor cortex's dominant effect on the body's contralateral side (Prieur, 2018). The asymmetric tonic neck reflex (ATNR) is a behavior in which neonates turn and hold their head to one side. Simultaneously, the ipsilateral arm stretches outward. The contralateral arm bends at the elbow. This position affords the opportunity for the infant to reinforce spatial mapping between the ipsilateral hand and the opposite brain hemisphere. The ATNR can be observed repeatedly to gain an approximation of an infant's head orientation preference, which has been related to the development of hand preference. This connection has been implicated in the development of hand preference (Goodwin & Michel, 1981), and hand preference has been related to the development of language (Nelson, Campbell, & Michel, 2014). Specifically, infants with an early right-hand preference scored higher on a standard language assessment at two years of age than infants with a late right or left-hand preference. This project extends this line of research by examining the relation between head orientation preference, hand preference, and language. Twelve infants were observed at 4, 8, and 12 weeks of age for their head orientation preference. At 12 and 16 weeks, and at 6, 7.5, 9, and 11 months, infants' hand preferences were observed. The hand preference assessment was performed at 12 and 16 weeks by hanging objects in the visual midline, while the infant was in a semi-reclined position. The hand that reached towards the objects was then recorded. Similarly, at later months, the infant was seated at a table, and a researcher presented objects on the table surface at the midline of the infant. These observations were recorded and later coded for lateralized reaching behaviors. Finally, the project seeks to relate these lateralized behaviors to language by conducting a language assessment on each child. It is expected, based on previous research by Nelson et al. (2014), that infants with early right-lateralized behaviors will show higher language scores than infants with later developing lateralized behaviors or those with a weak lateralized preference. Examining the relation between lateralized motor behaviors and language helps us determine the relation between these behaviors.
Mercado-Ramos, Danieli, "Do Lateralized Motor Behaviors Predict Language Development Across Infancy?" (2021). Psychology. 13.