vision + thresholds

sensation

detecting physical energy (a stimulus) from the environment and converting it into neural signals

perception

selection, organization, and interpretation of sensation

psychophysics

a study of the relationship between physical characteristics of stimuli and psychological experience with them

gustav fechner

founder of experimental psychology, established psychophysics, and came up with absolute threshold

absolute threshold

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

what experiments did fechner and weber carry out

absolute threshold experiments with light photons and sound waves

subliminal threshold

when stimuli are below ones absolute threshold for conscious awareness

difference threshold (AKA just noticeable difference)

minimum difference between two stimuli required for detection 50% of the time

webers law

two stimuli must differ by a constant minimum percentage (rather than amount) to be perceived as different

signal detection theory

predicts how and when we detect the presence of a faint stimulus (signal) amid background noise(other stimulation); SDT assumed that there is no single absolute threshold and detection depends on: persons exeprience, motivation, expectations, and level of fatique

SDT matrix

the observer decides whether they hear the tone or not, based on the signal being present or not; this translates into four outcomes. different for everyone

what is the most important sense

vision

how does vision work

rays of light hit cornea, which pass through the pupil. the lens bend the rays and focuses the light on the retina. the lens changed the shape to focus on the image, and accommodation occurs. as the light energy hits the retina, rods and cones are activated and send neurochemical signals through bipolar and ganglion cells to your thalamus via optic nerve. it ideally hits the fovea, and they will take the light waves and process them back. after it reaches the thalamus, the neurochemical signals are distributed to the rest of the brain

sensory transduction

transformation of stimulus energy into neural impulses

phototransduction

conversion of light energy into neural impulses the brain can understand

hue is determined by

length of wavelength

short v. long wavelength

short = blueish color and high pitch sounds

long = redish color and low pitch sounds

intensity is determined by

amount of energy in a wave determined by amplitude (height)

great amplitude wavelength =?

bright colors and loud sounds

small amplitude wavelength =?

dull colors, soft sounds

cornea

transparent tissue where light enters the eye. protects the eye and keeps it moist, and removes dirt

iris

muscle that expands and contracts to change the size of the pupil for light

pupil

hole (absence of structure) that expands or contracts bc of iris and the amount of light coming in

lens

focuses light rays on retina

astigmatism

lens is football shaped instead of spherical

accomodation

lens changing shape to help focus near or far objects on retina

nearsighted v. far sighted

nearsighted: eye curve is elongated

farsighted: eye curve is squished

fovea

point of central focus

retina

contains sensory receptors that process visual info and sends it to the brain; the light sensitive inner surface of the eye; literal brain tissue

rods

b&w, night vision, all over the place, are about 120 million

cones

color, detail, primarily in fovea, 6 million

bipolar cells

hands message to ganglion

ganglion cells

send messages to optic nerve

blindspot

the only part of the retina that doesnt contain rods or cones. the optic nerve goes to the brain

feature

nerve cells in the visual cortex respond to specific features, such as edges, angles, and movement

shape

temporal lobe activity occurs as people look at shoes, faces, chairs, and houses

parallel processing

brain processes several aspects of the stimulus simultaneously. this is two parts of the same stimuli, not two different

trichromatic theory (helmholtz)

normal retina contains 3 receptors that are sensitive to red, blue, and green, says every color seen is just a mixture of these light waves; RESPOND TO STIMULI

-colorblindness proves this

-ishihara test tests this

opponent-process theory (hering)

we process 4 primary colors combined in pairs of red-green, blue-yellow, and black-white; signals are processed transmitted to visual cortex

color constancy

color of an object remains the same under different illuminations; however, when context changes the color of an object may look different

color processing occurs in two stages. what are they

1) response to stimuli - trichromatic theory

2) signals are processed/transmitted to visual cortex (opponent-process theory)

dark adaptation

when it suddenly becomes dark and gradual increase in sensitivity to low levels of light

sensory adaptation

diminished sensitivity as a result of constant stimulation

sensory habituation

diminished sensitivity due to regular exposure

perceptual set (mental set)

tendency to see something as a part of group - speeds up signal processing

inattentional blindness

failure to notice someting because you’re so focused on another task

change blindness

failure to notice a change in the scene

cocktail party effect

notice your name across the room when its spoken, even if you werent paying attention

visual capture

visual system overwhelms all others

constancies

recognize that objects do not physically change despite changes in sensory input

phi phenomenon

adjacent lights link on/off in succession - looks like movement

stroboscopic movement

motion produced by rapid succession of slightly varying images