Infant Object Recognition: Two- and Three-Dimensional Visual Processing

Visual attention and recognition memory in infancy are highly dependent on the type of stimulus the infant is familiarized to and the conditions of familiarization. For example, in studies that initially exposed infants to test stimuli in laboratory settings (e.g., Courchesne, Ganz, & Norcia, 1981; Reynolds & Richards, 2005), the Negative Central (Nc) event-related potential (ERP) component associated with infant visual attention has shown greater amplitude for novel compared to familiar stimuli. Conversely, when initial stimulus exposure occured outside of the laboratory and the stimulus was highly familiar, studies have shown greater amplitude Nc to familiar compared to novel stimuli (e.g., de Haan & Nelson, 1997, 1999; Moulson, Shannon, & Nelson, 2011). This study investigated differences in attention and recognition memory for 6-month-old infants familiarized with an object in either a 2-D and 3-D controlled familiarization in a laboratory setting. Following familiarization, attention and recognition memory were measured during a standard ERP recognition memory procedure using 2-D photographic images of the familiar and novel objects. The Nc ERP component was used as a measure of visual attention, and the Late Slow Wave (LSW) ERP component as a measure of recognition memory. There was increased Nc ERP amplitude to the novel stimulus among infants in the 2-D condition. However, no significant differences in Nc amplitude based on stimulus type were found for infants in the 3-D condition. Analysis of the LSW showed a main effect for stimulus type, with greater amplitude positive LSW to the novel stimuli across familiarization conditions and electrode sites. These results indicate that familiarization with an object in 2-D or 3-D has differential effects on the salience hierarchy of familiar compared to novel stimuli in subsequent testing. At the same time, infants were able to fully process the familiar object under both familiarization conditions.