History of Visual Perception

Extramission

Ancient Greek theory suggesting that a fire-based beam is emitted from the eyes to gain information about the environment, endorsed by Plato and Euclid.

Intromission

Ancient Greek theory proposing that a portion of the environment enters the eye to form an image of the world, supported by scholars like Empiricus.

Stereopsis

Discovered by Alhazen, the ability to perceive depth and 3D structures from 2D retinal images.

Refraction

Also discovered by Alhazen, the bending of light as it passes from one medium to another, crucial for vision.

Absolute Threshold

Coined by Fechner, the minimum intensity needed for a stimulus to be detectable by human perception.

Difference Threshold

Concept developed by Fechner, indicating the minimum change required in a stimulus for it to be perceived.

Just Noticeable Difference

Ernst Weber's rule stating that the noticeable difference in a stimulus is a constant proportion of the original stimulus.

Fechner's Law

Proposed by Fechner, the logarithmic relationship between perceived intensity and actual stimulus intensity.

Unconscious Inference

Idea developed by Helmholtz, suggesting that perception is an indirect process based on cognitive relationships between action and sensation.

Gestalt Psychology

Approach emphasizing that perception occurs as a process of categorizing elements into a whole, not as individual components.

Swinging Room Experiment

An experiment where infants and adults were placed in a room with moving walls to study the importance of optic/visual information in determining balance and perception.

Gibson's Theory

Emphasizes the role of optic flow and visual information in perception, highlighting the significance of environmental cues over top-down or mechanical knowledge.

Visual Illusions

Phenomena that challenge Gibson's theory by demonstrating the role of neural processing in perception, suggesting that some perceptions are influenced by past knowledge and memories.

Top-Down Perception

Richard Gregory's approach that argues sensory input alone is insufficient to understand the world, emphasizing the role of past knowledge and memories in forming hypotheses about the environment.

Ambiguous Stimuli

Stimuli that can lead to multiple perceptions or hypotheses, illustrating the importance of neural processing and top-down mechanisms in perception.

Nativist Approach

The belief that certain aspects of perception and cognition are innate, contrasting with constructivist theories that emphasize learning and past experiences in forming hypotheses about the environment.