Sensation and Perception (Chapter 6)

Comprehensive vocabulary flashcards covering sensation, perception, sensory thresholds, visual and auditory pathways, skin and body senses, and the chemical senses (taste and smell).

Sensations

How our body detects external physical stimuli and converts them into a format that the brain can use; the fundamental, elementary components of an experience.

Perception

How we recognize, interpret, and make sense of sensory information.

Parallel Processing

The brain taking all sensory information from the environment and processing it simultaneously.

Transduction

The process by which sensory receptor cells transform external stimuli into electrical impulses (action potentials) that travel to the brain via the nervous system.

Supraliminal Perception

The conscious detection or noticing of a stimulus that is present in the environment.

Subliminal Perception

The processing of sensory information when a stimulus is present in the environment but not consciously noticed.

Absolute Threshold

The tipping point where an individual reaches a $50/50$ chance of correctly identifying that a given stimulus is present.

Signal Detection Theory

A framework describing our ability to detect a real or desired stimulus occurring amid other random or intervening stimuli.

Human Visible Spectrum

The narrow band of electromagnetic radiation sensitive to the human eye, spanning wavelengths between $380\,\text{nm}$ and $760\,\text{nm}$.

Hue

The dimension of light perceived as color, determined by the wavelength of light.

Brightness

The dimension of visual sensation determined by the intensity or amplitude of light waves.

Saturation

The relative purity of light; light containing only one wavelength is completely saturated, whereas light containing equal mixtures of all wavelengths appears white.

Sclera

The white outer layer of the eye that provides the eyeball with its shape and structural integrity.

Iris

The colored muscle ring of the eye that regulates the amount of light entering through the pupil.

Pupil

The opening in the center of the iris through which light enters the interior of the eye.

Pupillary Reflex

The involuntary, bilateral alteration of pupil size controlled by cranial nerves to adjust to varying levels of illumination.

Cornea

The curved, transparent outer layer covering the iris and pupil that bends incoming light to help focus images onto the back of the eye.

Lens

A flexible, transparent structure composed of clear cells that bends and alters its curvature to fine-tune visual images onto the retina.

Accommodation

The physiological process whereby the eye's lens changes shape to focus light: flattening to focus on distant objects and fattening to focus on nearby objects.

Rods

Photoreceptors located primarily in the periphery of the retina (numbering around $120{,}000{,}000$) that operate with high sensitivity in dim light to process dark, basic shapes.

Cones

Photoreceptors located primarily in the center of the retina (numbering around $6{,}000{,}000$) that function best in high light levels to provide color vision, fine detail, and clarity (the 4 C's: Color, Clear, Concise, and Center).

Optic Disc (Blind Spot)

The point in the retina where axons from ganglion cells converge to exit as the optic nerve, leaving an area completely devoid of photoreceptors that the brain fills in.

Feature Detectors

Specialized neurons in the visual cortex discovered by Hubel and Wiesel that respond selectively to specific features of a stimulus, such as bars of light at particular angles, edges, movement, or lengths.

Trichromatic Theory of Color Vision

The theory proposing that color perception is driven by three distinct cone types in the retina that respond maximally to red, green, or blue wavelengths, comparing their relative activations.

Opponent Process Theory of Color Vision

The theory stating that visual system cells beyond the photoreceptors process colors in antagonistic pairs (red vs. green, blue vs. yellow, black vs. white) by increasing firing to one color while decreasing firing to the other, which explains negative afterimages.

Bottom-Up Processing

Sensory analysis that begins with raw physical stimuli delivered to the sensory receptors; stimulus-driven processing.

Top-Down Processing

Information processing guided by higher-level mental processes, such as prior knowledge, beliefs, and expectations about how the world is organized; conceptually driven processing.

Law of Proximity

A Gestalt grouping principle stating that elements physically close to one another are perceived as belonging together as part of the same object.

Law of Similarity

A Gestalt grouping principle stating that visual items sharing similar physical properties (such as shape or color) are perceived as belonging to the same set.

Law of Closure

A Gestalt grouping principle stating that the brain tends to fill in gaps to perceive incomplete figures as unified, complete wholes.

Law of Good Continuation

A Gestalt principle stating that when lines intersect or are interrupted, we tend to perceive them as continuous, smooth, flowing lines.

Law of Common Fate

A Gestalt grouping principle stating that visual elements moving in the same direction at the same speed are perceived as a single group.

Monocular Depth Cues

Visual depth cues that require the use of only one eye, including linear perspective, relative size, overlap, shadows, and haze.

Linear Perspective

A monocular depth cue wherein parallel lines receding into the distance appear to converge toward a single vanishing point.

Binocular Depth Cues

Depth information obtained by comparing the slightly differing sensory inputs received by both eyes.

Retinal Disparity

A binocular cue for perceiving depth that calculates the difference between the slightly different images projected onto the two retinas.

Convergence

A binocular neuromuscular depth cue based on the inward rotation of the eyes as an object moves closer to the viewer.

Sound

A repetitive fluctuation in the pressure of a transmitting physical medium, such as air or water.

Pitch

The perceptual dimension of sound determined by wave frequency, measured in hertz ($\text{Hz}$).

Loudness

The perceptual dimension of sound determined by wave amplitude, measured in decibels ($\text{dB}$).

Timbre

The perceived acoustic quality or complexity of a sound distinguishing it from other sounds of identical pitch and loudness.

Pinna

The visible external cartilaginous flap of the outer ear that funnels and captures sound waves.

Tympanic Membrane (Eardrum)

The thin middle-ear membrane that vibrates back and forth in response to arriving sound waves.

Ossicles

The tiny middle-ear bones (malleus/hammer, incus/anvil, and stapes/stirrup) that mechanically amplify and transmit vibrations to the inner ear.

Cochlea

The fluid-filled, snail-shaped inner-ear structure where sound vibrations are transduced into neural impulses.

Basilar Membrane

The flexible structure running along the bottom of the cochlea embedded with hair cells that physically vibrates in response to fluid movement.

Place Theory

The pitch perception theory asserting that specific sound frequencies activate specific locations along the cochlea's basilar membrane.

Frequency Theory

The pitch perception theory holding that pitch is coded by the rate of nerve impulses traveling up the auditory pathway, where a higher firing rate signals a higher pitch.

Anterior Auditory Stream

The auditory processing pathway traveling forward to the frontal lobe that specializes in identifying 'what' a sound is.

Posterior Auditory Stream

The auditory processing pathway projecting to the parietal lobe that specializes in analyzing 'where' a sound originates (sound localization).

Somatosensation

The bodily sensory system encompassing all processes that detect and convey physical information about the body and its interactions with the environment.

Mechanoreceptors

Pressure-sensitive sensory receptor cells embedded in the skin that transduce mechanical stimuli (intensity, duration, and position of touch) into neural signals.

Thermoreceptors

Specialized subcutaneous receptor cells responsive to temperature changes, comprising six distinct mammalian types categorized into cold fibers and warm fibers.

Cold Fibers

Thermoreceptive nerve fibers that increase their firing rate of neural impulses in response to a cooling of the skin.

Warm Fibers

Thermoreceptive nerve fibers that fire vigorously in response to an increase in skin temperature.

Nociceptors

Free nerve endings in the skin that act as pain receptors, activating when exposed to stimuli intense enough to threaten or cause tissue damage.

Gate-Control Theory

The model proposing that pain signals transmitted to the spinal cord can be gated or blocked by neural mechanisms in the brain: stimulation of large nerve fibers closes the gate, while small fiber activity opens it.

Kinesthesis

The body sense that detects limb position and movement through specialized stretch-sensitive receptors in skeletal muscles called muscle spindles.

Vestibular Sense

The sensory system maintaining balance, posture, and spatial orientation via fluid movement within the inner ear's semicircular canals and vestibule.

Chemoreceptors

Sensory receptor cells that detect chemical molecules dissolved in fluids or dispersed in the air to produce the senses of smell and taste.

Olfaction

The chemical sense of smell, initiated when airborne odorants bind to the cilia of receptor cells lining the upper nasal cavity and project to the olfactory bulb.

Gustation

The chemical sense of taste, mediated by taste buds responding to bitter, sour, sweet, salty, umami, and fatty taste qualities.

Flavor

The holistic sensory experience of food, synthesized from gustation, olfaction, mouthfeel, visual presentation, and cognitive expectations.

Papillae

Small visible projections covering the tongue's surface that house taste buds.

Taste Buds

Sensory organs situated within papillae (numbering around $10{,}000$), each containing $20\text{--}50$ receptor cells that regenerate roughly every $10\,\text{days}$.

Capsaicin

The active chemical compound found in spicy foods that binds to heat-detecting nociceptors rather than taste receptors, triggering pain pathways and subsequent endorphin release.

Synesthesia

A rare neurological condition present in $2\text{--}4\%$ of the population in which stimulation of one sensory pathway leads to automatic, involuntary experiences in a secondary, unrelated sensory pathway.

Misophonia

A neurological condition characterized by intense negative emotional reactions (such as rage, disgust, or severe anxiety) to specific auditory triggers like chewing, pen clicking, or breathing.