Packet 3: Sensation and Perception

Sensation

when receptors in sense organs are activated by input from the environment

Transduction

converting outside stimuli into electrochemical messages for the brain

Sensory interaction

senses working together (e.g., smell affecting taste)

Synesthesia

stimulating one sense triggers a sensation in another

Just noticeable difference (JND)

smallest detectable difference between two stimuli, 50% of the time

Absolute threshold

lowest level of a stimulus detectable 50% of the time

Signal detection theory

predicts when a faint signal will be detected amid noise

Sensory adaptation

receptors become less responsive to an unchanging stimulus

Habituation

the brain stops paying attention to unchanging info

Visual accommodation

lens changes thickness to focus near or far

Myopia (nearsightedness)

distant objects blurry; focus falls in front of the retina

Hyperopia (farsightedness)

close objects blurry; focus falls behind the retina

Photoreceptors

rods and cones that turn light into neural signals

Optic nerve

carries visual info from the retina to the brain

Rods

periphery; detect shape, movement, and dim light; no color

Fovea

center of the retina, packed with cones

Cones

detect color and fine detail in bright light

Blind spot

where the optic nerve leaves the eye; no rods or cones

Dark adaptation

eyes adjusting to darkness (rods, 20-30 min)

Light adaptation

eyes adjusting to bright light (cones, 1-2 min)

Trichromatic theory

three cone types (red, green, blue); about the eye

Opponent-process theory

opposing pairs (red/green, blue/yellow, black/white); about the brain

Afterimages

an image that lingers after the stimulus is gone

Monochromatism

total color blindness

Dichromatism

only two cone types work (most common: red-green)

Prosopagnosia (face blindness)*

can't recognize faces

Blindsight*

responding to visual stimuli without consciously seeing them