Week+4

Shape constancy

The phenomenon where perceived 3D shape does not change when the 2D retinal shape changes due to changes in 3D viewing direction.

Perceptual constancy

A cognitive process where the perception of an object’s geometrical or physical characteristics remains constant, even when the retinal image changes.

Object vision vs. Spatial vision

Object vision is processed by the temporal cortex (shapes), while spatial vision is processed by the parietal cortex (distances and sizes).

Mental rotation

The cognitive process by which individuals visualize the rotation of a shape in their mind, affecting their percept of the original shape.

Recognition by components (Biederman, 1987)

A theory stating that objects are recognized by the arrangement and presence of symmetrical parts called 'geons', facilitating qualitative recognition.

Symmetry in shape constancy

The property of an object that allows for reliable shape constancy, as symmetrical objects can produce consistent 3D perceptions.

Edelman's findings (1995)

Edelman demonstrated reliable shape constancy with morphs of structured objects, such as animals, but overlooked the importance of symmetry.

Buelthoff & Edelman (1992) study

An experiment using amorphous stimuli which concluded that humans can only store 2D images of 3D objects, contradicting mental rotation findings.

Asymmetric vs Symmetrical stimuli

Symmetrical stimuli tend to produce better shape constancy performance compared to asymmetrical stimuli, particularly at high rotation angles.

Natural vs Unstructured stimuli

Natural stimuli (like animals) tend to lead to better perception in shape constancy experiments compared to unstructured stimuli.

Depth perception

The ability to perceive the world in three dimensions and judge distances, which influences shape perception.

Li & Pizlo's hypothesis

Suggests that if shape perception is rooted in depth perception, performance should be the same across different types of stimuli.

Inverse problem in vision

The challenge of determining an object's 3D shape from its 2D retinal image, leading to potential failures in shape constancy.

Experimental stimuli classifications

Objects can be classified from symmetrical polyhedra to non-planar asymmetric polyhedron based on their simplicity or regularity.

Human visual representation

The idea that the human visual system may not always produce accurate 3D representations of complex or unstructured shapes.