Perception, Cognition & Intelligence: Visual Processing and Functional Brain Organisation

Comprehensive vocabulary flashcards covering the historical, physiological, computational, and clinical principles of visual perception from Lectures 1 through 7.

Emission Theory (Extramission Theory)

An early philosophical theory supported by thinkers such as Plato, proposing that visual perception occurs because the eyes emit active rays or "eye beams" that intercept objects in the environment.

Intromission Theory

The optical theory established by Alhazen (Ibn al-Haytham) demonstrating that vision occurs when light rays emitted by an external source reflect off surfaces in all directions and enter the eye.

Lightness

The perceptual dimension spanning from black through gray to white, which physically corresponds to perceived reflectance—the permanent property determining what percentage of light a surface reflects (roughly $90\%$ for white, $3\%$ for black).

Brightness

The perceptual dimension spanning from dim to bright, which physically corresponds to perceived luminance—the transient, absolute intensity of light reflected in the direction of the observer's eye (measured in $\text{Cd/m}^2$).

Sensation

The initial, raw reception of physical stimulation by sensory receptors before cognitive interpretation or meaningful context is applied (such as sensing a pure red hue or sweetness).

Perception

The meaningful psychological interpretation and conscious awareness of sensory input, combining incoming sensory signals with experience and cognitive context (such as identifying that a rose is red and smells fragrant).

Molyneux's Problem

A philosophical question posed to John Locke in 1688 asking whether an individual born blind who learned to differentiate a sphere and a cube by touch would immediately recognize and name them by sight upon gaining vision.

Bottom-Up Processing

Sensory data processing driven strictly by external stimulus properties, proceeding from lower sensory stages to higher cognitive centers in a largely uniform manner across observers.

Top-Down Processing

Perceptual processing driven by higher-order cognitive influences, including past experiences, memory, knowledge, expectations, and instructional framing.

Sapir-Whorf Hypothesis

The principle of linguistic relativity asserting that the specific structure and vocabulary of an individual's native language shape, structure, and constrain how they think and perceive the world.

Berlin & Kay's Colour Hierarchy

A 1969 linguistic framework showing that basic colour terms evolve in languages across seven universal stages: Stage I (white and black), Stage II (red), Stage III (green or yellow), Stage IV (yellow and green), Stage V (blue), Stage VI (brown), and Stage VII (purple, orange, grey, and pink).

Qualia Problem

The fundamental philosophical dilemma concerning whether individual conscious, subjective internal experiences of sensations (such as the perceived redness of a flower) are identical across different individuals.

Bayes' Theorem

A mathematical principle in probability theory ($P(A|B) = \frac{P(B|A) \times P(A)}{P(B)}$) used to model perceptual processing, explaining how the visual system updates internal hypotheses about the world based on prior experience and sensory evidence.

Ambient Optic Array

A concept developed by James Gibson in ecological optics describing the complex, structured pattern of intersecting light rays converging at every point in space after reflecting off environmental surfaces.

Compound Eye

An optical system found in insects composed of thousands of individual ommatidia units that sample the visual field into a mosaic of receptor signals rather than focusing onto a single chamber.

Refraction

The bending of light rays that occurs when crossing the boundary between two optical media of different densities, bending toward the surface normal when entering a denser medium due to reduced velocity.

Humpty-Dumpty Problem

The challenge of explaining how disparate visual features (such as motion, shape, colour, and location) processed separately across distinct cortical areas are unified into a single coherent visual percept.

Double Dissociation

A neuroscience method demonstrating functional independence by showing that damage to brain structure A impairs task X while sparing task Y, whereas damage to structure B impairs task Y while sparing task X.

Ventral Stream ("What" Pathway)

A visual pathway projecting from the primary visual cortex to the inferior temporal lobe that is responsible for conscious object recognition, form perception, and colour analysis.

Dorsal Stream ("Where" / "How" Pathway)

A visual processing stream projecting from the primary visual cortex to the parietal lobe responsible for spatial awareness, motion analysis, and guiding visual motor action.

Patient DF

A patient who suffered temporal lobe damage from carbon monoxide poisoning, causing visual form agnosia that impaired conscious orientation matching while sparing visuomotor action in a posting task.

Brodmann Areas

Anatomical classifications of the cerebral cortex developed by Korbinian Brodmann, segmented based on cytoarchitectonics (variations in cellular structure and tissue architecture).

Retinotopy

The orderly topographical mapping of the visual field onto cortical tissue, such that adjacent points on the retina stimulate adjacent neurons within the primary visual cortex ($V1$).

Anomalous Trichromacy

A congenital condition affecting colour discrimination—predominantly red-green colour deficiency inherited along sex chromosomes—in which all three cone types are present but shifted in spectral sensitivity.

Blindsight

A clinical condition where patients with lesions in primary visual cortex ($V1$) report complete subjective blindness in the affected hemifield yet discriminate visual stimuli at levels well above chance.

Functional Segregation

A neural model stating that the brain consists of specialized modules that interact within distributed networks to carry out complex operations that individual areas cannot accomplish alone.

Diffusion Tensor Imaging (DTI)

An MRI technique that tracks the directional diffusion of water molecules along axonal pathways to map the physical trajectories and orientation of white matter tracts without revealing direction of signal flow.

Split-Brain Syndrome

A neuropsychological condition following surgical severance of the corpus callosum, preventing interhemispheric communication and isolating visual processing between the left and right hemispheres.

Broca's Area

A specialized motor-speech region in the frontal lobe of the dominant hemisphere, damage to which causes expressive aphasia characterized by non-fluent speech despite intact language comprehension.

Wernicke's Area

A specialized cortical region in the posterior superior temporal lobe essential for language processing, damage to which results in fluent but meaningless speech combined with impaired receptive language.

STSa Face-Selective Neurons

Single cells identified by David Perrett in the anterior superior temporal sulcus of primates that respond selectively to faces, facial expressions, gaze direction, and biological movements.

Psychophysics

The quantitative scientific discipline that investigates the relationship between physical stimuli and the subjective psychological sensations and perceptual thresholds they produce.

Troxler Fading

The perceptual fading and ultimate disappearance of unchanging, unmoving visual stimuli in the peripheral field when an observer fixates steadily on a stationary central target.

Colour Constancy

The visual system's capacity to perceive an object as retaining its surface colour despite substantial variations in the spectral composition of the illuminating light source.

Metamers

Physically dissimilar spectral power distributions of light that elicit identical perceptual colour sensations because they evoke the exact same relative activation profile across the three cone photoreceptors.

Motion Aftereffect (Waterfall Illusion)

A perceptual aftereffect documented by Robert Addams in 1834 at the Fall of Foyers, where sustained adaptation to continuous unidirectional movement causes stationary stimuli to appear to move in the opposite direction.

Ratio Model for Motion Aftereffect

A theoretical opponent model positing that stationary perception reflects balanced baseline activity between opposing direction channels, whereas selective adaptation fatigues one channel and shifts the baseline ratio toward the opposite direction.

Transparent Motion

A visual stimulus presentation in which two distinct directional motion vectors occupy the exact same spatial region simultaneously, appearing as two overlapping surfaces gliding across each other.

Wollaston Illusion

A facial perception illusion described in 1834 by William Hyde Wollaston demonstrating that the apparent direction of an identical set of eyes shifts based on the orientation and structure of the surrounding face.

Thatcher Illusion

A face-processing illusion described by Peter Thompson showing that inverted local features (such as inverted eyes and mouth) appear relatively normal in an inverted face but look grotesquely distorted upright.

Binocular Disparity

The slight horizontal difference between the retinal images received by the left and right eyes due to their physical separation, serving as the biological cue for stereoscopic depth perception.

Amblyopia

A visual disorder ("lazy eye") stemming from strabismic misalignment, unequal refractive power, or physical light deprivation during development, causing the brain to suppress input from one eye.

Random Dot Stereograms (RDS)

Stereoscopic stimuli developed by Béla Julesz composed of random pixel patterns with no monocular form cues, demonstrating that stereopsis and disparity processing can occur prior to object recognition.

Binocular Rivalry

A phenomenon of perceptual alternation occurring when disparate, incompatible visual images are presented simultaneously to each eye, leading consciousness to switch spontaneously between them.

Visual Neglect

A clinical attention disorder usually caused by right posterior parietal damage in the dorsal stream, causing patients to fail to perceive, respond, or attend to stimuli located in contralesional (left) space.

Motion Blindness (Akinetopsia)

A rare neurological condition caused by bilateral lesions to cortical area MT/V5 that eliminates the ability to perceive continuous fluid motion, reducing vision to a series of frozen static frames.

Dazzle Camouflage

A deceptive visual design system developed by British naval officer Norman Wilkinson in 1917 using complex, contrasting geometric patterns to disrupt an observer's estimation of a ship's speed, heading, and distance.