Sensory Perception and Visual Processing: Key Concepts and Theories

Sensation

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

Perception

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

Bottom-up processing

Analysis that begins with the sensory receptors and works up to the brain's integration of sensory information.

Top-down processing

Information processing guided by higher-level mental processes, such as experience and expectations.

Selective attention

Focusing conscious awareness on a particular stimulus.

Cocktail party effect

Ability to focus on one voice among many.

Inattentional blindness

Failing to see visible objects when our attention is elsewhere.

Change blindness

Failing to notice changes in the environment.

Transduction

The process of converting one form of energy into another; in sensation, transforming stimulus energies (sights, sounds, smells) into neural impulses.

Absolute threshold (Fechner)

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

Signal detection theory

Predicts when we will detect weak signals amid background noise depending on experience, motivation, and alertness.

Difference threshold (Just Noticeable Difference)

Minimum difference a person can detect between two stimuli half the time.

Weber's Law

To be perceived as different, two stimuli must differ by a constant minimum percentage (not amount).

Subliminal messages

Stimuli below the absolute threshold.

Priming

The activation (often unconsciously) of certain associations that affect perception or memory.

Sensory adaptation

Diminished sensitivity as a result of constant stimulation.

Perceptual set

A mental predisposition to perceive one thing and not another.

Context

The environment or situation influencing perception.

Motivation

Desires and goals that can bias perception.

Emotion

Feelings that can change how we interpret stimuli.

Wavelength

Determines hue (color).

Amplitude

Determines intensity (brightness).

Cornea

Protects the eye and bends light.

Iris

Colored muscle controlling pupil size.

Pupil

Adjustable opening where light enters.

Lens

Focuses light onto the retina through accommodation (changing shape).

Retina

Contains receptor cells (rods and cones).

Rods

Detect black, white, and gray; best in low light.

Cones

Detect color; best in daylight.

Bipolar and ganglion cells

Transfer visual information to the optic nerve.

Optic nerve

Sends visual information to the brain.

Blind spot

Area where the optic nerve leaves the eye; no receptor cells.

Fovea

Central focus area with many cones.

Young-Helmholtz Trichromatic Theory

Retina contains three color receptors (red, green, blue).

Opponent-Process Theory

Opposing retinal processes (red-green, blue-yellow, black-white) enable color vision.

Afterimages

Seeing complementary colors after staring at an image.

Gestalt

The whole is greater than the sum of its parts; the brain forms meaningful wholes.

Figure and Ground

Organization of visual field into objects (figure) and surroundings (ground).

Proximity

Grouping nearby figures together.

Continuity

Perceiving smooth, continuous patterns.

Closure

Filling in gaps to create a complete image.

Visual Cliff

Demonstrates depth perception in infants.

Retinal disparity

Difference between images from both eyes; greater disparity means the object is closer.

Relative size

Smaller objects are perceived as farther away.

Relative height

Higher objects are perceived as farther away.

Relative motion

Objects closer move faster.

Interposition

An object blocking another appears closer.

Linear perspective

Parallel lines appear to converge with distance.

Light and shadow

Shading gives depth cues.

Stroboscopic movement

Rapid series of images creates the illusion of motion (like a flipbook).

Phi phenomenon

Illusion of movement when lights blink quickly in succession.

Color and Brightness Constancy

Perceive color/brightness consistently under changing lighting.

Shape and Size Constancy

Objects are perceived as the same shape/size even from different angles.

Perceptual adaptation

Ability to adjust to changed visual input (like new glasses).

Amplitude (sound)

Determines loudness.

Frequency

Determines pitch.

Eardrum (tympanic membrane)

Vibrates when struck by sound waves.

Middle ear

Contains ossicles (hammer, anvil, stirrup) that amplify vibrations.

Cochlea

Coiled, fluid-filled tube that triggers nerve impulses.

Oval window

Opening where vibrations enter the cochlea.

Basilar membrane and hair cells

Detect vibrations and send signals to the auditory nerve.

Auditory nerve

Carries impulses to the temporal lobe.

Sensorineural hearing loss

Damage to hair cells or auditory nerve (most common type).

Conduction hearing loss

Damage to the mechanical system conducting sound waves.

Cochlear implant

Device that converts sounds into electrical signals to stimulate the auditory nerve.

Place theory

Different sound waves stimulate different spots on the basilar membrane (explains high pitches).

Frequency theory

Rate of nerve impulses matches sound frequency (explains low pitches).

Volley principle

Neurons alternate firing to handle higher frequencies.

Sound localization

Brain determines direction of sound based on which ear hears it first and loudest.

Touch

Four basic sensations: pressure, warmth, cold, and pain.

Gate Control Theory

Spinal cord contains a 'gate' that blocks or allows pain signals.

Biological influences (pain)

Nerve fibers and genetics.

Psychological influences (pain)

Attention, expectations, and memories.

Controlling pain

Distraction, endorphins, and placebos.

Taste (gustation)

The sense of taste with five basic flavors: sweet, sour, salty, bitter, umami (savory).

Smell (olfaction)

Chemical sense where receptors in the nasal cavity send messages to the olfactory bulb (not through the thalamus).

Kinesthetic sense

Awareness of body parts' position and movement.

Vestibular sense

Sense of balance; semicircular canals in the inner ear detect head movement.