2.1 Perception
- Syllabus
- 2025
- Topic
- 2.1
- Level
- —
Learning objectives
2.1A—Explain how internal and external factors influence perceptionExplain how internal and external factors influence perception.• Perception is influenced by whether one primarily relies on external sensory information (bottom-up processing) or internal prior expectations (top-down processing).• Schemas and perceptual sets are internal factors that filter perceptions of the world.• Contexts, experiences, and cultural experiences and expectations are external factors that filter perceptions of the world.• Perceptual principles proposed by Gestalt psychology (closure, figure and ground, proximity, and similarity) help explain how humans organize their perceptual world.• Attention is an interaction of sensation and perception that is affected by internal and external processes.- i. Some experiences of attention can be selective, such as with the cocktail party effect, where people attend to mentions of their names or specific topics in loud or distracting environments.- ii. Inattention can lead to a type of “blindness” to aspects of the environment. Change blindness occurs when changes to the environment are not perceived due to inattention.2.1B—Explain how visual perceptual processes produce correct or incorrect interpretations of stimuliExplain how visual perceptual processes produce correct or incorrect interpretations of stimuli.• Binocular depth cues of retinal disparity (the difference between the images projecting onto the retina) and convergence (the merging of the retinal images by the brain) utilize images from each eye to provide perception of depth.• Monocular depth cues (relative clarity, relative size, texture gradient, linear perspective, and interposition) give the illusion of depth on flat or two-dimensional surfaces.- Exclusion: The AP Psychology Exam will only address the listed monocular depth cues in EK• Visual perceptual constancies maintain the perception of an object even when the images of the object in the visual field change.• Apparent movement can be visually perceived even when objects are not actually moving.
Perception Filters and Organizes Sensation
| Processing route | Primary influence |
|---|---|
| Bottom-up processing | External sensory information builds the percept |
| Top-down processing | Prior expectations guide interpretation of sensory information |
Schemas and perceptual sets are internal filters: what a person already expects can make one interpretation more likely. Context, experience, and cultural experiences and expectations are external factors that also filter what is perceived. Perception usually reflects an interaction rather than only one route.
| Gestalt principle | Organization move |
|---|---|
| Closure | Perceive an incomplete pattern as complete |
| Figure–ground | Separate a focal object from its background |
| Proximity | Group nearby elements |
| Similarity | Group elements that share features |
Attention selects only part of the available input. The cocktail party effect shows selective attention to personally relevant information, such as one’s name, in a distracting setting. Change blindness shows the limit: an environmental change may go unperceived when attention is elsewhere. Missing the change does not mean the eyes received no stimulation.
Depth, Constancy, and Visual Illusions
| Cue family | Information used | Included cues |
|---|---|---|
| Binocular | Comparison of input from both eyes | Retinal disparity: the retinal images differ; convergence: the brain merges the images |
| Monocular | Information available to one eye and usable on a flat surface | Relative clarity, relative size, texture gradient, linear perspective, interposition |
Depth cues make a two-dimensional retinal image useful for judging three-dimensional distance. The same rules can create an illusion of depth on a flat image, so a coherent interpretation is not always a literal property of the stimulus.
Visual perceptual constancies maintain a stable perception of an object even when its image in the visual field changes. Apparent movement is the complementary reminder that the visual system can perceive motion even when objects are not actually moving.
Binocular cues require information from both eyes; monocular cues do not. AP Psychology limits monocular depth cues here to the five listed in the table.