Effects of Stimulus Symmetry on Hierarchical Processing in Six-Month-Old Short- and Long-Looking Infants

The current study investigated the effects of stimulus symmetry on the processing of global and local stimulus properties by 6-month-old short- and long-looking infants through the use of event-related potentials (ERPs). When compared with asymmetry, symmetry has been associated with more efficient stimulus processing and more accurate memory for stimulus configuration (Attneave, 1955; Perkins, 1932). Previous research has shown that individual differences in infant visual attention are related to hierarchical stimulus processing, such that short lookers show a precedence effect for global processing, while long lookers demonstrate a local processing precedence (Guy, Reynolds, & Zhang, 2013). Based on the Information Processing Principles proposed by Cohen and colleagues (Cohen, Chaput, & Cashon, 2002), the presence of asymmetry was expected to direct attention to the local features of stimuli, leading short lookers to regress to a local processing strategy. Analysis of the late slow wave (LSW) indicated that short lookers attended to global stimulus properties, while long lookers attended to local stimulus properties. Nc analyses revealed an interaction of familiarization condition, looker type, and stimulus type at midline central electrodes. Short lookers in the asymmetric familiarization condition showed a greater amplitude Nc response to the familiar stimulus than stimuli novel in global configuration, which indicates that these infants maintained interest in the familiar stimulus after familiarization. It is likely that interest was maintained because the familiar stimulus was not fully processed. These findings indicate that infants’ ERP responses to hierarchical stimuli are impacted by individual differences in visual attention and stimulus symmetry.