The efficient and accurate resolution of a three-dimensional percept from a two-dimensional retinal image is a computational problem that depends upon the conjunction of sensory information with prior knowledge. A tendency to assume that light comes from above and to the left of the apex in typical testing cohorts of young, Western adults, is a well-documented visual prior governing the resolution of three-dimensional shape from the patterns of light and shading on the surface of objects. Though the existence of the light-from-above prior and the leftward bias has been described extensively in previous literature, their origins remain unclear. Two primary theories have been posited for the light-from-above prior: that it develops in response to the visual experience of light coming from above, or that it is a developmental default. The left bias is more complicated. In addition to theories of visual experience, the roles of culturally proscribed reading habits and of innate hemispheric asymmetry may explain why a greater amount of attention is preferentially allocated to the left side of space. Chapter 1 discusses the primary theories posited on the origins of the light-from-above prior and the leftward bias by reviewing literature from developmental and ageing populations and from studies of pseudoneglect. In Chapter 2, these theories were investigated experimentally in a cross-sectional sample of 95 Welsh (left-to-right readers) and 64 Israeli (right-to-left readers) children, aged 3-10 years. From the earliest age at which children could engage with the visual search game, they exhibited a clear light-from-above prior that closely resembled adults’ and did not change with age. Chapter 2 concludes that the light-from-above prior is likely fully mature by three years of age. Chapter 3 explores how priors change in later life by testing 67 adults aged 60+ on a shape judgement task. In this task, older adults judged the three-dimensional shape of geometric images in which the placement of light and dark lines yields an impression of depth. Group-level variability increased among older adults, reducing the consistent leftward bias typically observed at group-level in young, Western adults. Interestingly, sex-specific effects were observed, with women exhibiting greater reductions in the left bias than men and better performance on cognitive tests. In particular, there were statistically significant differences between the cognitive test scores of women who did, and did not, successfully engage with the experimental paradigm. Such changes suggest that later-life reductions in behavioural asymmetry reflect reductions in hemispheric asymmetry and, as such, are a positive compensatory mechanism for neural losses. In Chapter 4, I present three iterations of a new paradigm to test the ability to perceive shape-from-shading. This test demonstrates that shading gradients offer a perceptual advantage over the direction of luminance polarity, but also that a common control stimulus for shaded spheres might contain conflicting cues to orientation that makes it an inappropriate control, and furthermore suggests that opposing orientation biases exist for shaded versus non-shaded stimuli. Chapter 5 concludes the thesis, drawing together the evidence presented to argue for the role of innate hemispheric asymmetry in the development of light priors and for the role of biological factors in the degeneration of directional biases.