All 4 Terms & Definitions
- Gestalt principles
- Rules by which the visual system groups elements into organised percepts. Proximity: nearby elements are grouped together. Similarity: like elements are grouped. Continuity: contours are perceived as continuous. Closure: incomplete figures are perceptually completed. Figure-ground: the visual field is organised into a figure (the object of attention) and ground (the background). These reflect the brain's tendency to impose structure on ambiguous input.
- Perceptual constancies
- The tendency to perceive stable object properties despite changing sensory signals. Size constancy: we see a person as the same size whether near or far, even though retinal image size changes. Shape constancy: a door appears rectangular whether viewed straight-on or at an angle. Lightness constancy: surfaces maintain their apparent brightness across changes in illumination. Constancies require the brain to "factor out" viewing conditions from raw sensory data.
- Visual pathways
- The visual cortex processes information in two major streams from primary visual cortex (V1). The ventral ("what") stream runs to the inferior temporal cortex and processes object identity, colour, and face recognition. The dorsal ("where/how") stream runs to the posterior parietal cortex and processes spatial location, motion, and the guidance of action. Double dissociations in patients with selective lesions of each pathway confirm their functional independence.
- Top-down processing
- The influence of higher-level knowledge, expectations, and context on the interpretation of sensory input. We perceive what we expect as much as what is "out there." Context effects, priming, and the resolution of perceptual ambiguity all involve top-down processing. Distinguished from bottom-up (data-driven) processing, which begins with sensory features and builds to perception.