Sensory Perception and Visual & Auditory Theories in Psychology

Absolute threshold

The minimum stimulation needed to detect a particular stimulus 50% of the time.

Difference threshold

The minimum difference between two stimuli required for detection 50% of the time (also known as the JND).

Just noticeable difference (JND)

Another term for the difference threshold.

Sensation

The process by which our sensory receptors and nervous system receive and represent stimulus energies from our environment (the raw data).

Sensory adaptation

Diminished sensitivity as a consequence of constant, unchanging stimulation.

Sensory interactions

The principle that one sense may influence another, as when the smell of food influences its taste.

Signal detection theory

A theory predicting how and when we detect the presence of a faint stimulus (signal) amid background noise, based on a person's expectations, motivation, and experience.

Subliminal

Below one's absolute threshold for conscious awareness.

Synesthesia

A rare condition where stimulation of one sensory pathway leads to automatic, involuntary experiences in a second sensory pathway (e.g., 'hearing' colors).

Transduction

The process of converting one form of energy into another—specifically, converting stimulus energy (like light) into a neural message the brain can understand.

Weber's Law

The principle that, to be perceived as different, two stimuli must differ by a constant minimum percentage (a proportion) of the original stimulus.

Accommodation

The process by which the eye's lens changes shape to focus near or far objects on the retina.

Afterimage

A visual sensation that persists after the stimulus is removed, typically appearing in complementary colors (explained by Opponent-Process Theory).

Blind spot

The point at which the optic nerve leaves the eye; there are no receptor cells here, creating a patch where vision is blocked.

Blindsight

A condition in which a person can respond to a visual stimulus without consciously experiencing or seeing it.

Color blindness

The inability or decreased ability to see color or differences in color, typically due to a lack of certain cone types.

Cones

Photoreceptors concentrated in the fovea that function in daylight and detect fine detail and color.

Dark adaptation

The process by which the eyes increase their sensitivity in low light; involves the regeneration of visual pigments in the rods and cones.

Dichromatism

A form of color blindness where a person has only two types of cone photoreceptors instead of the normal three (e.g., red-green color blindness).

Farsightedness

A condition where nearby objects are seen as blurry but distant objects are clearly seen; caused by the eyeball being too short or the lens too flat.

Fovea

The central focal point in the retina, where the eye's cones cluster, providing the sharpest vision.

Hue

The dimension of color determined by the wavelength of light (e.g., blue, green, red).

Intensity

The amount of energy in a light wave (determined by amplitude), which we perceive as brightness.

Lens

The transparent structure behind the pupil that changes shape to help focus images on the retina.

Monochromatism

Complete color blindness, resulting in vision only in shades of gray, black, and white.

Nearsightedness

A condition where distant objects are blurry but nearby objects are clear; caused by the eyeball being too long or the lens too curved.

Optic chiasm

The point in the brain where the optic nerves from both eyes cross over and project to the opposite half of the brain.

Optic nerve

The nerve that carries neural impulses from the eye's retina to the brain.

Opponent-process theory

Theory that color is processed in opposing retinal pairs: red-green, yellow-blue, and white-black. Explains afterimages.

Photoreceptor

General term for the light-sensitive cells (rods and cones) in the retina that perform transduction.

Prosopagnosia (face blindness)

A neurological disorder characterized by the inability to recognize familiar faces.

Retina

The light-sensitive inner surface of the eye, containing the photoreceptors and layers of neurons where transduction occurs.

Rods

Photoreceptors that function best in dim light (twilight vision), detect black, white, and gray, and are located mainly in the retina's periphery.

Trichromatic theory

Theory that the retina contains three different color receptors (most sensitive to red, green, and blue) which, when stimulated in combination, produce the perception of any color.

Wavelength

The distance between the peaks of light waves; determines the perceived hue (color).

Amplitude

The magnitude (height) of a sound wave, which determines the perceived loudness.

Audition

The sense or act of hearing.

Cochlea

The coiled, fluid-filled tube in the inner ear where hair cells perform transduction of sound waves into neural signals.

Conduction deafness

Hearing loss caused by damage to the mechanical system that conducts sound waves (e.g., eardrum, middle ear bones).

Frequency

The number of complete wavelengths that pass a point in a given time; determines the perceived pitch.

Frequency theory

Theory that the rate of nerve impulses traveling up the auditory nerve matches the frequency of a low tone ($<1,000$ Hz).

Nerve deafness

Hearing loss caused by irreversible damage to the cochlea's hair cells or to the auditory nerves.

Pitch

A tone's experienced highness or lowness; depends on frequency.

Place theory

Theory that links the pitch we hear to the place where the cochlea's membrane is maximally stimulated; best for high-pitched sounds.

Sound localization

The ability to determine the origin/location of a sound in space by comparing differences in timing and intensity between the two ears.

Volley theory

A refinement of frequency theory; states that neural cells alternate firing in rapid succession (volley) to code for intermediate pitches ($1,000-5,000$ Hz).

Bitter, Sweet, Salty, Sour

Four of the five basic taste sensations (gustation).

Chemical sense

Any sense that involves the detection of chemical stimuli (gustation and olfaction).

Gustation

The sense of taste.

Medium taster

A person whose number of taste buds falls between the 'nontaster' and 'supertaster' ranges.

Nontaster

A person with fewer taste buds, generally having a reduced ability to taste bitterness.

Oleogustus

A proposed taste sensation referring to the taste of fat.

Olfaction

The sense of smell.

Pheromone

A chemical substance released by an animal that affects the behavior or physiology of others of its species (often related to olfaction).

Supertaster

A person with a significantly greater number of taste buds than average, leading to heightened taste sensitivity (especially to bitterness).

Umami

The fifth basic taste, translated as savory or 'essence of deliciousness,' typically triggered by glutamate.

Gate-control theory of pain

Theory that the spinal cord contains a neurological 'gate' that can block or allow pain signals to pass to the brain.

Kinesthesis

The system for sensing the position and movement of individual body parts using receptors in muscles, tendons, and joints.

Kinesthetic sense

Another term for Kinesthesis.

Pain

The unpleasant sensory and emotional experience associated with actual or potential tissue damage.

Phantom limb pain

The perception of pain or sensation in a limb that is no longer physically attached to the body.

Vestibular sense

The sense of body movement and position, including the sense of balance, using fluid-filled canals in the inner ear.

Warm

A specific sensation detected by thermosensory receptors in the skin.

Apparent movement

An illusion of movement created when two or more adjacent lights blink on and off in quick succession (Phi phenomenon).

Attention

The ability to focus selectively on a particular stimulus or task, which is a key component of Selective Attention and Selective Inattention.

Binocular depth cues

Depth cues that depend on the use of two eyes (retinal disparity, convergence).

Bottom-up processing

Analysis that starts with the raw sensory receptors and works up to the brain's interpretation (data-driven).

Change blindness

Failing to notice changes in the environment, often after a brief visual interruption.

Closure

A Gestalt grouping principle; we fill in gaps to create a complete, whole object.

Cocktail party effect

The ability to attend selectively to only one voice among many while filtering out other surrounding sounds.

Cognition

The mental activities associated with thinking, knowing, remembering, and communicating (the broad mental processes that drive top-down perception).

Context

The circumstances, setting, or background environment in which a stimulus is perceived. Context powerfully influences Top-down processing and our Perceptual set.

Convergence

A binocular depth cue; the extent to which the eyes move inward (converge) when looking at a near object.

Cultural expectations

The influence of the beliefs, values, and practices shared by a group of people on how sensory information is interpreted (drives perceptual set).

Depth perception

The ability to see objects in three dimensions (3D) and judge distance.

Expectations

A person's established beliefs, knowledge, or mental assumptions about what they are likely to encounter or perceive. Expectations are the primary drivers of Perceptual Set and Top-down processing.

External sensory information

The raw data received by the senses from the environment (input for bottom-up processing).

Figure-and-ground

The organization of the visual field into an object (figure) that stands out from its surroundings (ground).

Gestalt psychology

A school of thought emphasizing that we integrate pieces of information into meaningful wholes ('The whole is greater than the sum of its parts.').

Grouping

The perceptual tendency to organize stimuli into coherent groups (principles include proximity, similarity, continuity, closure).

Inattentional blindness

Failing to see visible objects when our attention is directed elsewhere.

Internal prior expectations

The influence of one's existing knowledge or beliefs on how sensory information is interpreted (drives top-down processing).

Interposition

A monocular depth cue; if one object partially blocks our view of another, we perceive it as closer.

Linear perspective

A monocular depth cue; parallel lines appear to meet in the distance.

Monocular depth cues

Depth cues available to either eye alone (e.g., interposition, linear perspective).

Perception

The process of organizing and interpreting sensory information, enabling us to recognize meaningful objects and events.

Perceptual constancy

Perceiving objects as unchanging (constant size, shape, lightness, color) despite changes in the retinal image or illumination.

Perceptual set

A mental predisposition to perceive one thing and not another, heavily influenced by expectations and context.

Proximity

A Gestalt grouping principle; we tend to group nearby figures together.

Relative clarity

A monocular depth cue; hazy, indistinct objects appear farther away than sharp, clear objects.

Relative size

A monocular depth cue; if two objects are presumed to be similar in size, the one that casts the smaller retinal image is perceived as farther away.

Retinal disparity

A binocular depth cue; the difference between the two slightly different images received by each retina; the greater the disparity, the closer the object.

Schema

A conceptual framework or mental model that organizes and interprets information.

Selective attention

The focusing of conscious awareness on a particular stimulus.

Selective inattention

The process of filtering out information that is not attended to.

Similarity

A Gestalt grouping principle; we tend to group similar figures together.

Texture gradient

A monocular depth cue; a gradual change from a coarse, distinct texture to a fine, indistinct texture signals increasing distance.

Top-down processing

Information processing guided by higher-level mental processes (experience, expectations) to construct perceptions (schema-driven).

Visual perceptual processes

The mechanisms in the brain responsible for interpreting and organizing visual sensory input.