Visual Perception of Orientation is Categorical near Vertical and Continuous near Horizontal

Abstract

Four experiments were conducted to examine whether visual-orientation information is perceived categorically. In experiments 1 and 3, adult participants sorted oriented line stimuli into broad oblique and narrow vertical or horizontal categories. Experiments 2 and 4 showed that categorical discrimination of orientation occurred only near the vertical-oblique boundary. The data indicate that there is categorical perception near vertical and more continuous perception near horizontal. The results are relevant to the debate over whether categorical perception is derived from perceptual structure, verbal coding, or within-task learning. In addition, the asymmetrical perception of orientation around vertical and horizontal is consistent with the possibility that there may be differences in the functional significance of orientation near the two main axes.

Evidence for mental subdivision of space by infants: 3- to 4-month-olds spontaneously bisect a small-scale area into left and right categories

“…This earlier finding stands in contrast to that reported presently in which infants in the same age range formed category representations for left versus right when the vertical bar was removed from the stimuli. The results are consistent with findings that left-right cues dominate above-below cues when both are available (Nicoletti, Umiltà, Tressoldi, & Marzi, 1988), evidence that left-right symmetry is more salient than above-below symmetry (Corballis & Beale, 1983), the outcome that categorical perception is sharper around vertical than it is around horizontal (Quinn, 2004b), and the idea that attention naturally distinguishes between left and right because of hemispheric specialization (Chatterjee, Southwood, & Basilico, 1999).…”

Atypical Categorical Perception in Autism: Autonomy of Discrimination?

“…However the same phenomenon was observed in other primates (Kuhl & Padden, 1982). Recent developments emphasize the fact that categorical perception occurs for learned categories such as man-made objects (Newell & Bü lthoff, 2002), identity of faces (Levin & Beale, 2000), gender of faces (Bü lthoff & Newell, 2004) or computer generated textures (Pevtzow & Harnad, 1997;see Harnad, 2003 for a review), as well as for more biologically constrained (or innate) categories, such as speech sounds, colors (Bornstein & Korda, 1984), line orientations (Quinn, 2004) or facial expressions (Calder, Young, Perrett, Etcoff, & Rowland, 1996;Etcoff & Magee, 1992). These phenomena can appear early in the learning of categories.…”

Color Perception in Children with Autism

“…Therefore, reduced categorical perception in autism may be limited to learned categories that are possibly mediated by more top-down mechanisms (Sowden & Schyns, 2006). Further research, testing for categorical perception in autism for other domains (e.g., orientation, Quinn, 2004) is needed to establish when categorization is atypical in autism. Gaining a better understanding of this may lead to a greater understanding of the activation and interaction of different levels of processing in autism.…”