Sensation and Perception

Flashcards covering the key concepts of sensation and perception, including sensory processes, thresholds, vision, and color perception.

Sensation

The process by which the sense organs gather information about the environment and transmit the information to the brain for initial processing.

Perception

The process by which the brain selects, organises, and interprets sensory information.

Psychophysics

The study of the relationship between physical stimuli and psychological experience.

Absolute Threshold

The minimum amount of stimulus energy that must be present for the stimulus to be detected 50% of the time.

Just Noticeable Difference (JND)

The lowest level of stimulation required to sense that a change in stimulation has occurred.

Weber's Law

The principle that the JND is a constant proportion of the original stimulus intensity.

Weber fraction

The ratio of change in intensity required to produce a JND.

Fechner's Law

The magnitude of a stimulus grows geometrically as the subjective experience of intensity grows arithmetically.

Steven's Power Law

The perceived intensity of a stimulus grows arithmetically, the actual magnitude of the stimulus grows exponentially.

Transduction

The process of converting physical energy or stimulus information into neural impulses.

Visible spectrum

The range of electromagnetic wavelengths that humans can see, approximately 400-750 nanometres (nm).

Cornea

The tough, transparent tissue covering the front of the eyeball for protection.

Pupil

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

Pupillary response

The dilation or constriction of the pupil in response to changes in ambient lighting or emotional/motivational states.

Retina

The layer at the back of the eye containing photoreceptors that transduce light into neural impulses.

Photoreceptors

Specialized cells in the retina (rods and cones) that transduce light energy into neural signals.

Rods

Photoreceptors that are more sensitive to light and are responsible for vision in dim light; not sensitive to wavelength and thus cannot distinguish color. Located in periphery.

Cones

Photoreceptors that are less sensitive to light and are responsible for detailed vision and color perception. Concentrated in the fovea.

Fovea

The central part of the retina with a high concentration of cones; responsible for detailed vision.

Bipolar cells

Cells in the retina that synapse onto photoreceptors and transmit signals to ganglion cells.

Ganglion cells

Cells in the retina whose axons form the optic nerve, carrying visual information to the brain.

Optic nerve

The nerve that carries visual information from the retina to the brain.

Pigmented epithelium

Dark layer behind the retina which absorbs stray photons.

Reflecting Tapetum

Is a reflective membrane that bounces the stray photons back through the photoreceptors again so they have a second chance of being absorbed, which increases the sensitivity of vision to low levels of light. And causes loss of acuity so why your cats or dogs eyes glow in the dark.

Young-Helmholtz (Trichromatic Theory)

The theory that color perception is based on the differential activation of three color receptors in the eye (red, green, blue).

Opponent-process theory

The theory that color perception is based on three antagonistic systems (black-white, red-green, blue-yellow).