Sensory, Attentional and Perceptual Processes
Overview
This domain explains how sensory organs detect stimuli and how attention and perception organise that information into meaningful experience. The exam tests thresholds, attention types, Gestalt principles, depth cues and illusions.
Core concepts
- Sensation is the detection of physical energy; perception is the interpretation of sensory input.
- Absolute threshold is the weakest detectable stimulus; difference threshold is the smallest detectable change. Sensory adaptation is reduced sensitivity after constant stimulation.
- Attention may be selective, divided or sustained; it filters competing information.
- Gestalt principles include figure–ground, proximity, similarity, closure and continuity.
- Depth cues are binocular (retinal disparity, convergence) and monocular (linear perspective, relative size, overlap, texture gradient, motion parallax).
- Perception can be bottom-up (data-driven) or top-down (concept-driven), and is influenced by perceptual set.
Worked example
A driver approaches a flat road sign but perceives it as tilted because of linear perspective. The retinal image is ambiguous, yet the brain uses monocular depth cues and past experience to interpret the scene. If the driver expects a hazard, top-down processing may make a neutral shape look threatening-an example of perceptual set.
Traps that cost marks
Do not say sensation and perception are identical. Do not confuse absolute with difference threshold. Selective attention is not the same as divided attention. Retinal disparity requires two eyes and is binocular. Illusions are systematic errors in perception, not evidence that the senses are useless.
Exam focus
Classify a cue or attention type and explain how organisation or expectation shapes perception.