Abstract
We previously demonstrated that 4-month-old infants responded with increased looking and oculomotor activity toward pictures of impossible cubes relative to possible ones, and they fixated specifically within the critical region of impossible cubes (p<.01) where the anomalous junction occurred, an effect that was not observed reliably in younger infants. This suggested that 4-month-olds selectively respond to local vertices (T-, Y-junctions) diagnostic of global coherence. However, it left open the question of whether 4-month-olds would systematically respond with increased visual interest to other novel impossible figures varying in type of geometric contours (curvilinear vs. straight-edges). We recorded eye movements from 4-month-old infants as they viewed images of possible and impossible objects. We hypothesized that infants would engage in active comparison of the objects, and that impossible figures would evoke increased scanning to ascertain global structural integrity. Infants looked longer (p<.03) and directed a greater number of fixations (p<.05) on impossible relative to possible cubes. Preference scores indicated infants’ partiality for the impossible cube differed from chance (p<.05). The effect of increased visual interest toward impossible figures generalized to other straight-edged stimuli, but not curvilinear ones. Furthermore, across all object pairs, infants initiated a greater number of fixations and looked an average of 300 ms longer in the lower halves of impossible figures relative to their possible mates (p<.05), whereas there were no reliable differences in fixation behavior in the top halves. The high degree of variability in infants’ fixation behaviors may be due to individual differences in selective looking or emerging sensitivity to pictorial depth, or may be a stimulus-dependent response that manifests exclusively with specific shapes (impossible cubes with salient manipulations of T- and Y-junctions). Our findings suggest that several mechanisms for selectively analyzing local depth relations and ascertaining information about global 3D shape develop rapidly in early infancy.
Meeting abstract presented at VSS 2013