ch.4 Flashcards
sensation
the detection of physical energy by sense organs
transduction
conversion of stimulus to electrical signal
perception
the brains interpretation of raw sensory input
sensation allows
us to gather intro from the external world
perception allows
us to make sense of that info
sensory adaption happens at sensory receptor level
a decrease in the noticeability of stimulus over time ex: get a smelling candle fall scent later doesn’t smell
absolute threshold
the smallest amount of a stimulus we can detect at least 50% of the time ex: a watch ticking 20 feet away you can hear
Just Noticeable Difference (JND)
the smallest change we can detect in stimulus strength intro to perception FALSE our perceptual experience is a direct translation of sensory input
pupil
hole that allows light into the eye
iris
colored part, muscle that controls the pupil
cornea
outside covering that helps protect and focus light
lens
disc that focuses light on the back of the eye
retina
membrane on the back of the eye containing sensory receptors
fovea
area on the retina where light is focused
optic nerve
transmits visual signals to the rest of the brain
why should i care about fovea?
light focuses on the fovea controls how well you see
myopia-nearsighted
light focuses too soon
hyperopia-farsighted
light focuses too late
photoreceptors
visual sensory receptors, located in the retina
cones
sense bright light and color
rods
sense dim light
where are cones concentrated?
concentrated at the fovea, very highly acuity
where are rods concentrated?
they are concentrated in the periphery, low acuity
Why should I care about rods?
you can use your knowledge of rods to improve your night vision, they get oversaturated in too much light ex: going to bathroom late at night can’t see
what do rods and cones connect to
they connect to ganglion cells
ganglion cells
carry visual info. from the eye to the brain, form the optic nerve
light (sunlight)
has all the wavelengths in it
Where are wavelengths absorbed
some by surfaces and others are reflected
where do objects get their color
from reflected light
subtractive color mixing
mixing pigment absorbs more light (looks darker) paint works this way
additive color mixing
mixing colored lights give off more lights (gets brighter) light works this way
trichromatic theory of color vision
idea that color vision is based on three primary colors blue, green and red
How many cones do we have that respond to blue, green and red
3 cones
patterns of activity between different cone types allows
us to see all possible colors
color blindness
occurs when one cone is missing, called dichromatic vision
statistics of color blindness
5% of men and .25% of women are colorblind
opponent process theory of color vision
we perceive things in terms of opponent color pairs, red, green, blue light or dark they inhibit each
ganglion cells pool incoming info from cones
send one signal about the color (either red or green etc) to the brain
bottom up processing
processing driven primarily by sensory input
top down processing
processing driven primarily by concepts beliefs or expectations
feature integration theory
objects are made up of features our cells detect separately color, shape etc.
what does feature detection involve?
parallel processing, all features can be sensed at once
what does feature integration involve?
serial processing, each objects features must be integrated one at a time
how does your brain decide what an object is?
gestalt principles of grouping
gestalt principles of grouping
cues that help us group features or parts into whole objects
proximity
physically close things are grouped
similarity
similar things are grouped
good continuation
continuous things are grouped
closure
gaps in borders are ignored to form a whole
symmetry
symmetrical things are grouped
figure-ground
foreground is grouped
common motion
things that more together are grouped
depth perception
ability to see in 3D
two kinds of depth perception
monocular cues, binocular cues
monocular cues
cues that require input from just one eye
binocular cues
cues that require input from both eyes
monocular depth cues
-relative size
distant objects look smaller ex: people in pictures who are closer are big
monocular depth cues
-texture gradient
texture of distant objects is less
ex: fields of flowers
interposition (monocular depth cues)
closer objects block further ones
ex: something blocking legs podium blocking still think she has legs
linear prospective (monocular depth cues)
lines coverage over distance
height in plane (monocular depth cues)
distant objects appear higher
light and shadow (monocular depth cues)
shadows cue 3D shapes ex: light to dark (dark to light holes)
motion paralax (monocular depth cues)
further things pass by slower
binocular depth cues
-binocular disparity
difference in retinal images, slight difference in the view from each eye
binocular convergence
binocular depth cues
difference in visual angle perceptual illusions
what is a lot of our perception based on?
a lot of our perception is based on expectations maintaining continuity
