Global visual processing is important for segmenting scenes, extracting form from background, and recognizing objects. Local processing involves attention to the local elements, contrast, and boundaries of an image at the expense of extracting a global percept. Previous work is inconclusive regarding the relative development of local and global processing. Some studies suggest that global perception is already present by 8 months of age, whereas others suggest that the ability arises in childhood and continues to develop in adolescence. We used a novel method to assess the development of global processing in 3-to 10-year-old children and an adult comparison group. We used Kanizsa illusory contours as an assay of global perception and measured responses on a touch screen while monitoring eye position with a head-mounted eye tracker. Participants were tested using a similarity match-to-sample paradigm. Using converging measures, we found a clear developmental progression with age such that the youngest children performed near chance on the illusory contour discrimination whereas 7-to 8-year-olds performed nearly perfectly, as did adults. There was clear evidence of a gradual shift from a local to a global processing strategy: Young children looked predominantly at and touched the pacman inducers of the illusory form, whereas older children and adults looked predominantly at and touched the middle of the form. These data show a prolonged developmental trajectory in appreciation of global form, with a transition from local to global visual processing between 4 and 7 years of age.
KeywordsKanizsa illusory contours; perceptual development; global processing; eye tracking; global form perception Visual information about objects is often incomplete. Parts of objects can be occluded, missing, or blend seamlessly into the background, yet adults perceive the objects as complete global forms rather than a collection of disconnected local elements. In the laboratory, adults perceive holistic contours of shapes based on illusory edges that have no
Author Manuscript Author ManuscriptAuthor ManuscriptAuthor Manuscript physical luminance, color, or texture boundary. How does this global perceptual ability come about? Although some researchers have found evidence for perception of illusory figures in young infants (e.g., Bertenthal, Campos & Haith, 1980;Kavsek, 2002;Otsuka & Yamaguchi, 2003;Bulf et al., 2011), others have reported that global form perception and discrimination of illusory shapes do not reach maturity until late childhood (Abravanel, 1982;Kimchi et al., 2005;Sherf et al., 2009;Hadad, Maurer & Lewis, 2010). Here, we used a novel approach-accuracy on a match-to-sample task paired with several measures of spontaneous manual and visual behaviors-to investigate the development of illusory contour perception as an assay of global form perception in children from 3 to 10 years of age. Our objective methods and converging behavioral evidence show a clear, protracted developmental program for global visual process...