Abstract
The structure of the environment includes more horizontal and vertical (i.e. cardinal) orientations than oblique orientations, meaning that edges tend to be aligned with or perpendicular to the direction of gravity. This bias in the visual scene is associated with a bias in visual sensitivity in adults. Although infants must learn to function in this biased environment, their immature motor control prevents them from consistently orienting themselves, relative to gravity. This study therefore asked whether cardinal orientations dominate human visual experience from early infancy or only from later in development, as motor control improves. We analyze video clips from head-mounted cameras, showing the egocentric perspective of 75 infants (1 to 12 mo) in their home environments in two communities (Indiana, USA vs. Tamil Nadu, India). We measured the distribution of orientations in each frame of these videos and found that horizontal and vertical orientations were overrepresented in infants from both countries. A cardinal orientation bias was evident even in the egocentric view of the youngest infants (3 wk) and became more prominent during the subsequent weeks of development. The early presence of a cardinal orientation bias in infants' visual input may serve as a consistent cue to gravity and ground planes, potentially influencing motor development and contributing to the formation of sensory, perceptual, and cognitive biases.