Sensation and Perception: Vision, Audition, and Higher-Level Processing

Comprehensive vocabulary flashcards covering color perception, depth and binocular space perception, visual attention, motion processing, auditory anatomy and physiology, sound localization, and music and speech perception.

Problem of Univariance

The principle stating that an infinite set of different wavelength-intensity combinations can elicit exactly the same response from a single type of photoreceptor, meaning a single receptor type cannot make color discriminations based on wavelength alone.

Trichromatic Theory of Color Vision

The theory (also known as the Young-Helmholtz theory) that the perceived color of any light is defined by the unique combined outputs of three receptor types (S-, M-, and L-cones).

Metamers

Different mixtures of wavelengths that look identical; more generally, any pair of stimuli that are perceived as identical despite physical differences.

Additive Color Mixing

A mixture of lights where all emitted wavelengths are combined and reflected directly to the eye, adding together their spectral outputs.

Subtractive Color Mixing

A form of filtering typically seen with pigments, where each added pigment absorbs (subtracts) specific wavelengths, and the perceived color is determined by the remaining unabsorbed wavelengths.

Cone-Opponent Cell

A neuron whose receptive field shows excitation to one cone type and inhibition to another (such as $L - M$ or $[L + M] - S$), found in the retina and lateral geniculate nucleus (LGN).

Opponent-Color Theory

Ewald Hering's theory that color perception is driven by paired opponent mechanisms: red versus green, blue versus yellow, and black versus white.

Unique Hue

Any of four colors (red, yellow, green, blue) that can be described using only a single color term without perceived traces of another chromatic component.

Double-Opponent Cell

A complex cortical neuron found in primary visual cortex that combines inputs from two LGN color-opponent cells and responds strongly to color boundaries and edges.

Negative Afterimage

A perceptual image seen after stimulus removal whose polarity is complementary to the original stimulus (e.g., green seen after staring at red, or yellow after blue) due to sensory adaptation of opponent mechanisms.

Achromatopsia

A complete inability to perceive colors caused by cortical damage to specialized color-processing regions (such as areas in V4).

Color Contrast

A perceptual effect in which the color appearance of one region induces the complementary opponent color in an adjacent, neighboring region.

Color Assimilation

A perceptual effect in which two closely interwoven colors bleed into each other, each taking on some of the chromatic character of the other.

Color Constancy

The tendency of a surface to appear roughly the same color across a wide range of illumination conditions by discounting the illuminant.

Occlusion

A nonmetrical monocular depth cue that provides relative depth ordering when one closer object physically obstructs part of an object behind it.

Texture Gradient

A monocular depth cue based on the systematic geometric reduction in the retinal image size and spacing of repeating visual elements as distance from the observer increases.

Familiar Size

A depth cue based on prior knowledge of the typical physical dimensions of an object, which can provide absolute metrical depth information when paired with retinal visual angle.

Aerial Perspective

A monocular depth cue based on light scattering by atmospheric particles, causing more distant objects to appear hazier, bluer, and lower in contrast.

Linear Perspective

A depth cue based on the projection of three-dimensional space onto a two-dimensional plane, where parallel lines receding into depth appear to converge at a vanishing point.

Motion Parallax

A depth cue in which the apparent movement of stationary objects depends on observer motion: objects closer than fixation appear to move faster and in an opposite direction relative to farther objects.

Binocular Disparity

The difference between the two retinal images of the same visual scene, providing the primary sensory basis for stereopsis.

Horopter (Vieth-Müller Circle)

The geometric circle of points in space that project to corresponding retinal points in the two eyes, producing zero binocular disparity.

Panum's Fusional Area

The narrow region of three-dimensional space immediately surrounding the horopter within which binocular single vision is achieved without diplopia.

Crossed Disparity

The sign of binocular disparity created by objects positioned closer to the observer than the horopter, displacing the retinal image to the left eye's right and the right eye's left.

Uncrossed Disparity

The sign of binocular disparity created by objects positioned beyond the horopter, displacing the retinal image to the left eye's left and the right eye's right.

Correspondence Problem (Binocular Vision)

The challenge faced by the visual system in determining which feature in the left eye's image corresponds to the identical feature in the right eye's image.

Binocular Rivalry

The alternating competition between the two eyes for conscious visual perceptual dominance when radically different, incompatible images are presented dichoptically.

Stereoacuity

A measure of the smallest difference in binocular disparity that can reliably yield a perceptual sensation of depth, measured in arc minutes.

Strabismus

A childhood ocular disorder involving the misalignment of the two visual axes such that a single target falls on the fovea of one eye and on extrafoveal retina of the other.

Selective Attention

The set of cognitive mechanisms that restricts perceptual processing to a specific subset of available sensory inputs, ideas, or locations in space.

Stimulus Onset Asynchrony (SOA)

The precise temporal interval measured between the onset of a cue and the subsequent presentation of a target or probe stimulus.

Feature Search

An efficient visual search task in which a target is defined by a single salient visual primitive (e.g., color or orientation), yielding a search slope of approximately $0\,\text{ms/item}$.

Conjunction Search

An inefficient visual search task where the target is defined by the co-occurrence of two or more distinct visual features, requiring serial self-terminating inspection.

Guided Search

A search process where attention is directed toward a prioritized subset of stimuli based on preattentively processed basic feature information (such as color, size, or orientation).

Scene-Based Guidance

The deployment of semantic and structural knowledge regarding natural environments to bias spatial attention toward plausible target locations within a scene.

Feature Integration Theory

Anne Treisman's theoretical framework proposing that elementary visual features are extracted preattentively in parallel across the visual field, but focal attention is required to bind them correctly to an object.

Illusory Conjunction

An incorrect psychological recombination of two distinct features belonging to different items in a visual scene, occurring when attention is diverted or overloaded.

Attentional Blink

The temporary reduction in ability to detect or identify the second of two rapid targets presented in a rapid serial visual presentation (RSVP) stream when the second appears within $200\text{--}500\,\text{ms}$ of the first.

Fusiform Face Area (FFA)

A specialized subregion of the fusiform gyrus in human extrastriate cortex that responds preferentially to faces over other object categories.

Parahippocampal Place Area (PPA)

A dedicated cortical region in the temporal lobe that activates strongly when observing images of places, spatial environments, and buildings.

Ensemble Statistics

The average value and distributional summary of properties (such as size, orientation, or color) extracted rapidly across a multitude of objects in a visual scene via the nonselective pathway.

Change Blindness

The failure to notice substantial visual alterations between two successive presentations of a scene when the change does not disrupt the central semantic gist.

Inattentional Blindness

The failure to perceive or consciously report a clearly visible, suprathreshold stimulus when attention is deeply focused on another task or item.

Visual Neglect

A neuropsychological condition resulting from unilateral parietal damage (typically in the right hemisphere) that impairs attention and conscious responsiveness to contralesional space or objects.

Balint Syndrome

A severe neurological disorder caused by bilateral parietal lobe lesions characterized by uncoordinated eye movements, poor spatial localization, and simultagnosia.

Simultagnosia

The inability to perceive or attend to more than one object at a time, resulting in extreme visual processing narrowing.

Apparent Motion

The illusory perception of smooth continuous movement generated by displaying static images in rapid succession across slightly different spatial positions.

Aperture Problem

The ambiguity inherent in viewing a moving contour through an isolated small receptive field or opening, where multiple different physical directions produce identical local motion signals.

Middle Temporal Area (Area MT / V5)

An extrastriate visual cortical region containing a high proportion of direction-selective neurons that combine local motion signals to compute global object motion.

Motion Aftereffect (MAE)

The perceptual illusion of movement in the opposite direction experienced after prolonged visual adaptation to continuous directional motion.

Interocular Transfer

The neural phenomenon where an adaptation effect induced by exposing one eye transfers to the other unexposed eye, demonstrating cortical mediation (at or beyond V1).

First-Order Motion

The motion of an object or pattern defined strictly by changes in physical luminance across space over time.

Second-Order Motion

The motion of an object defined by changes in texture, contrast, or flicker without differences in average luminance.

Optic Flow

The changing pattern of angular velocities and positions of environmental points projected across the retina as an observer travels through space.

Focus of Expansion (FOE)

The central, invariant origin point in an optic flow field from which all radial motion vectors expand outward during forward locomotion, specifying heading direction.

Tau ($\tau$)

An optical variable equal to the ratio of retinal image size to its rate of expansion, providing a direct metric to calculate time to contact (TTC) without computing physical distance or speed.

Comparator

A visual system mechanism that subtracts motor commands (efferent copy) sent to extraocular muscles from retinal image shifts to distinguish real object motion from observer eye movements.

Saccadic Suppression

The brief neurological attenuation of visual sensitivity that occurs during rapid saccadic eye movements to prevent the perception of blur and motion smear.

Akinetopsia

A rare neurological condition caused by lesions in cortical area MT characterized by an inability to perceive visual motion, producing a discontinuous series of static freeze-frames.

Decibel ($\text{dB}$)

A logarithmic unit used to quantify sound intensity or acoustic pressure relative to a standardized reference sound pressure level ($p_0$).

Fundamental Frequency

The lowest frequency component of a complex periodic sound wave, which predominantly determines its perceived musical pitch.

Timbre

The psychological quality or coloration of a sound that allows a listener to distinguish two complex tones having identical fundamental frequency, loudness, and duration.

Tympanic Membrane

A thin sheet of skin situated at the terminus of the external ear canal that vibrates synchronously with acoustic pressure fluctuations; the eardrum.

Ossicles

The three tiny bones of the middle ear (malleus, incus, stapes) that act as mechanical levers to concentrate sound energy from the large tympanic membrane onto the small oval window.

Acoustic Reflex

An involuntary protective middle-ear reflex in which the tensor tympani and stapedius muscles contract to dampen ossicle vibrations in response to sustained loud sounds.

Organ of Corti

The specialized sensory structure situated along the basilar membrane within the cochlea containing inner and outer hair cells, supporting cells, and auditory nerve fibers.

Tip Link

A tiny extracellular mechanical filament connecting the top of each stereocilium to its taller neighboring stereocilium that rapidly gates mechanosensitive ion channels during acoustic shear.

Place Code (Hearing)

The mechanism of auditory frequency tuning in the cochlea where high frequencies induce maximal basilar membrane displacement near the base, and low frequencies displace near the apex.

Characteristic Frequency (CF)

The specific frequency to which a given auditory nerve fiber or central auditory neuron responds at the lowest sound pressure threshold.

Phase Locking

The firing of an auditory nerve fiber at a specific, consistent phase point in the periodic cycle of a sound wave, generating a temporal frequency code.

Volley Principle

The hypothesis that a population of phase-locked auditory neurons can collectively encode frequencies higher than $1000\,\text{Hz}$ by staggering their action potentials across successive sound wave cycles.

Tonotopic Organization

The systematic spatial arrangement of auditory sensory structures and cortical areas according to frequency, preserved from the basilar membrane to primary auditory cortex (A1).

Equal-Loudness Curve

A psychoacoustic plot displaying sound pressure level ($\text{dB SPL}$) against acoustic frequency for tones that are perceived as having identical loudness by human listeners.

Critical Bandwidth

The range of frequencies within an auditory filter channel beyond which increasing the bandwidth of a masking noise ceases to produce additional masking of a test tone.

Sensorineural Hearing Loss

A form of auditory impairment originating from damage to cochlear hair cells or the auditory nerve fibers, commonly stemming from ototoxicity, acoustic trauma, or aging.

Interaural Time Difference (ITD)

The difference in the arrival time of an acoustic wave front between the ipsilateral and contralateral ears, used to localize sound sources across azimuth.

Azimuth

The horizontal angle of a sound source relative to the central forward axis of the head, measured in clockwise degrees from $0^\circ$ (front) to $180^\circ$ (rear).

Medial Superior Olive (MSO)

A brainstem nucleus in the superior olivary complex that receives bilateral auditory inputs and serves as the primary neural locus for computing interaural time differences.

Interaural Level Difference (ILD)

The difference in sound pressure level arriving at the two ears caused by the acoustic shadow of the head, primarily effective for frequencies greater than $1000\,\text{Hz}$.

Lateral Superior Olive (LSO)

A brainstem nucleus in the superior olivary complex that compares excitatory inputs from the ipsilateral ear with inhibitory inputs from the contralateral ear to calculate interaural level differences.

Cone of Confusion

A conical surface extending outward from the ear canal containing all spatial positions that generate identical interaural time and interaural level differences.

Head-Related Transfer Function (HRTF)

A spectral filtering profile describing how the anatomical structures of the pinna, ear canal, head, and torso alter sound pressure intensities at different frequencies across spatial coordinates.

Missing-Fundamental Effect

The psychoacoustic phenomenon whereby listeners perceive a pitch corresponding to the fundamental frequency of a harmonic series even when that lowest frequency has been physically eliminated from the sound.

Attack and Decay

The temporal dynamics of sound amplitude, where attack denotes the initial rate of amplitude rise (onset) and decay denotes the subsequent decrease in intensity (offset).

Auditory Scene Analysis

The perceptual grouping and decomposition of a combined acoustic waveform generated by multiple overlapping environmental sources into distinct perceptual streams and objects.

Auditory Restoration Effect

A cognitive phenomenon where an interrupted or masked portion of a continuous acoustic signal (such as speech or music) is perceptually reconstructed by the brain when replaced with white noise.

Tone Height

The psychological dimension of musical pitch that increases monotonically with physical sound frequency, running vertically along the musical helix.

Tone Chroma

The perceptual sound quality shared by musical notes that possess the same relative octave position (e.g., all C notes), represented as rotational position around the musical helix.

Octave

The interval separating two sound frequencies that have an exact ratio of $2:1$, producing an acoustic perceived identity of note category.

Phonation

The physical process in speech production wherein expelled pulmonary air vibrates the vocal cords (folds) within the larynx.

Articulation

The mechanical manipulation of the vocal tract's geometry by altering the positions of the tongue, jaw, lips, and soft palate (velum) to shape acoustic resonances.

Formants

Acoustic resonance peaks in the speech spectrum (designated $F_1$, $F_2$, $F_3$) resulting from vocal tract shaping that distinguish specific vowel sounds.

Coarticulation

The articulatory phenomenon in running speech where the acoustic and muscular properties of successive phonemes overlap due to the mechanical inertia of vocal tract articulators.

Categorical Perception

The perceptual phenomenon where continuously varying acoustic speech signals (such as gradual changes between 'bah', 'dah', and 'gah') are perceived as discrete, sharply bounded phonemic categories.

McGurk Effect

A multimodal perceptual illusion demonstrating that visual speech information (such as video of someone mouthing 'gah') alters auditory perception of an acoustic sound (such as 'bah'), resulting in the perception of a third phoneme ('dah').

Statistical Learning (Speech)

The computational capacity demonstrated by infants to segment continuous streams of speech into individual words by calculating the transitional probabilities of adjacent syllables.