psych of perception chapter 3

Question 1

visible spectrum for human

Answer 1

ranges from 400 to 700 nanometers

Question 2

name the electromagnetic wave spectrum from short wavelenghts to long wavelengths

Answer 2

gamma, x-ray, ultraviolet, visible light, infrared, microwaves, radio waves

Question 3

what is fovea

Answer 3

point of central focus
all-cone foveal vision results in high visual acuity

Question 4

ligth patway in the eye

Answer 4

light enters the eye through the pupil and is focused by by the cornea and lens to sharp image on retina

Question 5

distribution on retina

Answer 5

fovea consist solely of cones,
peripheral retina has both rods and cones,
more rods then cones in periphery

Question 6

number of cones and rods

Answer 6

120 million rods and 6 million cones

Question 7

blind spot

Answer 7

place where the optic nerve leaves the eye

Question 8

lens

Answer 8

adjust shape for object distance (accomodation results when ciliary muscles are tightened, which causes the lens to thicken)

Question 9

light focusing

Answer 9

cornea, which is fixed, accounts for 80% of focusing,
the lens, which adjust shape for object distance, accounts for the other 20%

Question 10

presbyopia

Answer 10

presbyopia is the gradual loss of your eyes’ ability to focus on nearby objects
due to hardening lens and weakening of ciliary muscles

Question 11

myopia

Answer 11

can’t see well from futher away (nearsightedness)
image is focused in front of the retina

Question 12

myopia is caused by

Answer 12

cornea or lens bends too much light
eyeball is too long

Question 13

hyperopia

Answer 13

can’t see objects from up close well
focus point is behind retina
eyeball too short

Question 14

what is dark adaption

Answer 14

process of increasing sensitivity in the dark

Question 15

dark adaptaion curve

Answer 15

sensitivity increases in two stages (3-4min)
then sensitivity levels off for 7-10min - the rod-cone break
stage two shows increased sensitivity for another 20 to 30min

Question 16

threshold

Answer 16

threshold for light is lowest in the middle of the spectrum
use monochromatic light to determine threshold at different wavelenghts

Question 17

rod spectral sensitivity

Answer 17

more sensitive to short-wavelenght light
most sensitive at 500nm

Question 18

cone spectral sensitivity

Answer 18

most sensitive at 560nm

Question 19

Purkinje shift

Answer 19

enhanced sensitivity to short wavelenghts during dark adaptaion when the shift from cone to rod vision occurs

Question 20

rods and cones sends signals vertically through

Answer 20

bipolar cells
ganglion cells
ganglion axons

Question 21

rods and cones sends signals horizontally through

Answer 21

between receptors by horizontal cells
between bipolar and between ganglion cells by amavrine cells

Question 22

rods

Answer 22

rods are more sensitive to light than cones
take less light to respond
cannot distinguish detail

Question 23

rods convergence

Answer 23

rods have greater convergence, which results in summation of the inputs of many rods into ganglion cels increasing likelihood of response

Question 24

lateral inhibition

Answer 24

emphasizing the boundaries between things

Question 25

simultaneous contrast

Answer 25

if surrounding region is brighter then cells that are covering this brighter region will create more suppresion signal to the center which makes it appear darker

Question 26

receptive field

Answer 26

area of retina that affects firing rate of a given neuron in the circuit (imaginary spot on the retina)

Question 27

center and surround ares of receptive field result in

Answer 27

excitatory-center-inhibitory surround
inhibitory-enter-excitatory surround

Question 28

center-surround antagonism

Answer 28

when stimulated, the center and surround of RF cause the opposite responses to the corresponding ganglion cell