Perception & Sensation

Sensation

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

Absolute Threshold

The minimum intensity of a stimulus that one can detect at least 50% of the time.

Just-Noticeable Difference (JND)

The smallest change in the intensity of a stimulus that one can detect.

Weber's Law

States that the JND for a stimulus is a constant proportion of the original stimulus intensity.

Sensory Adaptation

Occurs when sensitivity to a constant stimulus decreases over time.

Sensory Interaction

The principle that one sensory modality can influence another.

Synesthesia

A condition where stimulation of one sensory pathway leads to automatic, involuntary experiences in a second sensory pathway.

Cornea

The eye's outermost layer, providing most of the eye's optical power by bending incoming light.

Retina

A light-sensitive layer at the back of the eye containing photoreceptor cells that convert light into neural signals.

Blind Spot

An area on the retina where the optic nerve exits the eye, lacking photoreceptors.

Pupil

The opening in the iris that allows light to enter the eye.

Iris

The colored part of the eye surrounding the pupil that contains muscles to adjust pupil size.

Lens

A transparent structure behind the iris that focuses light onto the retina.

Accommodation

The process by which the lens changes shape to focus on objects at varying distances.

Nearsightedness (Myopia)

Occurs when light is focused in front of the retina, making distant objects appear blurry.

Farsightedness (Hyperopia)

Occurs when light is focused behind the retina, making close objects appear blurry.

Photoreceptors

Cells in the retina (rods and cones) that convert light into neural signals.

Rods

Photoreceptor cells sensitive to low light, essential for vision in dim conditions.

Cones

Photoreceptor cells responsible for color vision and visual acuity.

Transduction

The process by which sensory stimuli are converted into neural signals.

Trichromatic Theory

The theory that color vision is based on the activation of three types of cones sensitive to red, green, and blue light.

Opponent Process Theory

A theory that explains color perception through opposing retinal processes.

Fovea

A small central pit in the retina that is densely packed with cones.

Afterimages

Visual perceptions that continue after the original stimulus has been removed.

Ganglion Cells

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

Dichromatism

A form of color blindness where one type of cone is missing or dysfunctional.

Monochromatism

Total color blindness occurring when two or all three cone types are nonfunctional.

Prosopagnosia

A neurological disorder that impairs the ability to recognize faces.

Blindsight

A condition where individuals can respond to visual stimuli without conscious awareness of seeing.

Pinna (Auricle)

The visible part of the outer ear that collects sound waves.

Eardrum (Tympanic Membrane)

A thin membrane that vibrates in response to sound waves.

Cochlea

A spiral-shaped, fluid-filled structure in the inner ear responsible for converting sound vibrations into neural signals.

Auditory Nerve

Carries neural signals from the cochlea to the auditory cortex in the brain.

Wavelength

The distance between successive peaks of a sound wave, determining pitch.

Amplitude

The height of a sound wave, determining loudness.

Place Theory

Posits that different parts of the cochlea are activated by different frequencies of sound.

Frequency Theory

Suggests that the rate of nerve impulses matches the frequency of the sound wave.

Volley Theory

Proposes that groups of auditory nerve fibers fire in rapid succession to encode higher frequencies.

Sound Localization

The process by which we determine the direction and distance of a sound source.

Conduction Deafness

Occurs when there is a problem in the transmission of sound waves through the outer or middle ear.

Sensorineural Deafness

Caused by damage to the inner ear or auditory nerve pathways.

Transduction of Olfactory Stimuli

The process by which odorant molecules are detected and converted into neural signals.

Pheromones

Chemical signals released by individuals that affect the behavior of others in the same species.

Gustation (Taste)

The sense that detects chemicals in food via taste receptors on the tongue.

Supertasters

Individuals with more taste buds and greater sensitivity to tastes.

Chemical Senses

Olfaction and gustation, which interact to create the perception of flavor.

Skin Receptors

Various types of receptors in the skin that detect touch, pressure, temperature, and pain.

Gate Control Theory

Proposes that there is a neural 'gate' that can modulate the transmission of pain signals to the brain.

Phantom Limb Sensation

The sensation of pain or movement in a limb that has been amputated.

Vestibular Sense

The sensory system responsible for detecting balance and spatial orientation.

Kinesthesis (Proprioception)

The sense of the position and movement of body parts.

Perception

The process of organizing, interpreting, and making sense of sensory information.

Bottom-Up Processing

Raw sensory data received from the environment processed to construct perception.

Top-Down Processing

Preconceptions and knowledge that influence how sensory information is interpreted.

Schemas

Cognitive frameworks that help organize and interpret information.

Perceptual Sets

Tendencies to perceive certain aspects of sensory data while ignoring others.