Perception n sensation

Sensation

The process by which our sensory receptors and nervous system receive and represent stimulus energies from our environment.

Transduction

The conversion of one form of energy into another. In sensation, transforming stimulus energies into neural impulses.

Absolute threshold

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

Just-noticeable difference (AKA Difference Threshold)

The minimum difference between two stimuli required for detection 50% of the time.

Sensory adaptation

Diminished sensitivity as a consequence of constant stimulation.

Weber’s law

The principle that, to be perceived as different, two stimuli must differ by a constant minimum percentage (rather than a constant amount).

Sensory interaction

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

Synesthesia

A condition in which one sensory pathway leads to involuntary experiences in another sensory pathway, like "seeing" sounds.

Retina

The light-sensitive inner surface of the eye, containing the receptor rods and cones plus layers of neurons that process visual information.

Blind spot

The point at which the optic nerve leaves the eye, creating a "blind" spot because no receptor cells are located there.

Visual nerve

Nerves that carry visual information from the retina to the brain.

Lens

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

Accommodation

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

Nearsightedness

A condition in which nearby objects are seen more clearly than distant objects because distant objects focus in front of the retina.

Farsightedness

A condition in which distant objects are seen more clearly than nearby objects because the image of near objects is focused behind the retina.

Photoreceptors

Specialized cells in the retina that respond to light and consist of rods and cones.

Rods

Retinal receptors that detect black, white, and gray; necessary for peripheral and twilight vision.

Cones (blue, green, red)

Retinal receptors that are concentrated near the center of the retina and function in daylight. They detect fine detail and color (red, green, blue).

Trichromatic theory

Theory that the retina contains three types of color receptors—one most sensitive to red, one to green, one to blue—which, when stimulated in combination, can produce the perception of any color.

Opponent-process theory

The theory that opposing retinal processes (red-green, yellow-blue, white-black) enable color vision.

Afterimages

Sensations that linger after the stimulus is removed, often showing in complementary colors.

Ganglion cells

Cells in the retina that receive visual information from photoreceptors and transmit it to the brain through the optic nerve.

Dichromatism

A type of color blindness resulting in the absence of two types of cones.

Monochromatism

Total color blindness, where the person only perceives shades of grey.

Prosopagnosia

An inability to recognize faces, also known as face blindness.

Blindsight

A condition in which a person can respond to visual stimuli without consciously experiencing them.

Wavelength

The distance from the peak of one light or sound wave to the peak of the next; determines color in light and pitch in sound.

Pitch

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

Amplitude

The height of a wave's crest, which determines loudness in sound and intensity in light.

Loudness

The perceived volume of sound, determined by the amplitude of the sound wave.

Pitch perception

The ability to distinguish between different frequencies of sound.

Place theory

Theory that links the pitch we hear with the place where the cochlea's membrane is stimulated.

Volley theory

Theory that neurons alternate firing to carry higher frequency sounds by summing their output.

Frequency theory

Theory that the rate of nerve impulses traveling up the auditory nerve matches the frequency of a tone, thus enabling pitch perception.

Sound localization

The ability to identify the origin of a sound in direction and distance.

Conduction deafness

Hearing loss caused by damage to the mechanical system that conducts sound waves to the cochlea.

Sensorineural deafness

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

Olfactory system

The sensory system responsible for smell.

Thalamus

The brain's sensory control center, located on top of the brainstem; it directs sensory messages to the cortex.

Gustation

The sense of taste.

Sweet, sour, salty, bitter, umami, oleogustus

The six primary taste sensations.

Taste receptors

Sensory receptors located on the tongue responsible for taste perception.

Supertasters

Individuals who experience taste sensations more intensely due to a higher number of taste receptors.

Medium tasters

Individuals who have an average number of taste receptors.

Nontasters

Individuals with fewer taste receptors, experiencing weaker taste sensations.

Warm/cold receptors

Sensory receptors in the skin that detect temperature changes.

Gate control theory

Theory that the spinal cord contains a gate that either blocks pain signals or allows them to pass on to the brain.

Phantom limb

The sensation of pain or other feelings in an amputated limb.

Vestibular sense

The sense of body movement and balance, primarily controlled by the semicircular canals.

Semicircular canals

Three fluid-filled canals in the inner ear responsible for the sense of balance.

Kinesthesis

The sense of body part movement and position.

Bottom-up processing

Analyzing sensory information by starting with the raw data received by sensory receptors and moving toward complex interpretations in the brain.

Top-down processing

Perception guided by higher-level knowledge, experience, expectations, and motivations, affecting the way sensory information is interpreted.

Schema

A mental framework or concept that helps organize and interpret information in the brain.

Perceptual set

A mental predisposition to perceive one thing and not another, influenced by expectations, emotions, and experiences.

Gestalt psychology

A psychological approach that emphasizes our tendency to integrate pieces of information into meaningful wholes.

Closure

The tendency to fill in gaps in an incomplete image to create a complete, whole object.

Figure and ground

The organization of the visual field into objects (the figures) that stand out from their surroundings (the ground).

Proximity

A principle of Gestalt psychology that states objects near each other are perceived as a group.

Similarity

A Gestalt principle stating that objects similar in appearance are more likely to be perceived as belonging together.

Attention

The process of focusing awareness on a particular stimulus while ignoring others.

Selective attention

The focusing of conscious awareness on a particular stimulus while excluding others.

Cocktail party effect

The ability to focus on a single voice among a multitude of conversations, especially when your name is mentioned.

Inattentional blindness

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

Change blindness

Failing to notice changes in the environment due to a lack of focused attention.

Binocular depth cues

Depth cues that depend on the use of two eyes, including retinal disparity and convergence.

Retinal disparity

A binocular cue for perceiving depth based on the difference between the images in each eye; the greater the disparity, the closer the object.

Convergence

A binocular cue for perceiving depth; the extent to which the eyes converge inward when looking at an object.

Monocular depth cues

Depth cues that require the use of only one eye, including relative size, interposition, and linear perspective.

Relative clarity

A monocular cue that suggests objects that appear clearer and sharper are closer than those that are hazy.