3D shape-from-shading relies on a light source prior that does not change with age

Area of Science:

• Cognitive Psychology
• Developmental Psychology
• Visual Perception

Background:

• The light-from-above prior is crucial for inferring 3D shape from shading.
• Young Western adults exhibit an implicit bias for light sources positioned above and to the left.
• Prior research yielded conflicting findings on the developmental trajectory of assumed light source direction.

Purpose of the Study:

• To investigate the developmental emergence and stability of the light-from-above prior and leftward bias in children.
• To examine the relationship between age, sensitivity to shading, and light source prior direction.
• To assess the influence of global processing preference and scanning habits on the left bias.

Main Methods:

• A cross-sectional study involving children aged 5-11 years.
• An explicit shape judgment task was employed to measure light source priors.
• Reading proficiency and cancellation task performance were used to assess scanning habits.

Main Results:

• The light-from-above prior and leftward bias were present in children as soon as they showed sensitivity to shading information, irrespective of age.
• No significant correlation was found between global processing preference or scanning habits and the magnitude of the left bias.
• While the ability to interpret shape-from-shading improved with age, the direction of light source priors remained unaffected by age.

Conclusions:

• The development of the light-from-above prior and leftward bias does not necessitate a prolonged maturation period.
• Light source prior direction appears to be developmentally stable once it becomes measurable in children.
• These findings suggest that fundamental assumptions about light direction are established early in visual development.