Chapter 4: Sensation Flashcards
Weber’s Law (p. 137-139)
the size of the difference threshold is proportional to the intensity of the standard stimulus
the more intense the stimulus, the more stimulus intensity has to be increased before observer notices a change
ex) difference between a backpack weighing 25lbs and one weighting 25.5 lbs, but you won’t notice a smaller difference in lbs
Fechner’s Law
strength of a sensation is proportional to the logarithm of physical stimulus intensity
Muller
key to sensation lies simply in which nerves are being stimulated
stimulation of the optic nerve causes the sense of seeing ; stimulation of the auditory nerve cause the sense of hearing
sensory coding
(Muller)
the process through which nervous system represents the qualities of the incoming stimulus
perceptual sensitivity
ability to detect a signal
decision criteria
organism’s rule for how much evidence it needs before responding
signal detection theory
perceiving or not perceiving a stimulus is actually a judgement about whether a momentary sensory experience is due to background noise alone or to the bckgrnd noise + a signal
how people make decisions as to when a particular stimulus is present & when it isnt
What 2 factors are at work in signal detection?
- Sensitivity (how well subject can see/hear stimulus
2. Response Bias (how willing a subject is to say he heard stimulus when he is not certain)
payoff matrix
pattern of benefits and costs associated with certain types of responses
(ratio of amount of reward for success to reward for failure)
visible spectrum
light that we can see out of the broader electromagnetic spectrum
(ranges from 400-700)
amplitude
determines brightness
Fovea
area at the pupil’s center where cones are plentiful and visual acuity is greatest
Optic Nerve
bundle of fibers that proceeds from each retina to the brain
Blind spot
where there are no photo receptors (p.164)
Rods
photoreceptors in the retina that respond to lower light intensities and give rise to colorless (achromatic)
Rods (night vision)
photoreceptors in the retina that respond to lower light intensities and give rise to colorless (achromatic) sensations
contain photopigment rhodipsin
Cones (day vision)
photoreceptors in the retina that respond to greatet light intensities and give rise to color (Chromatic) sensations
Duplex Theory of Vision
Rod Photo receptors are much more sensitive to low levels of light and over a broader range of wave
Duplex Theory of Vision
Rod Photo receptors are much more sensitive to low levels of light and over a broader range of wave frequencies than are the cone receptors
Unlike the cone receptors, they do not code for color
Young-Helmholtz (Trichromatic) Theory
human color vision= 3 sets off cones
- one is sensitive to a wavelength of 440 nm (blue)
- one is sensitive to wavelength of 530nm (green)
- one is sensitive to wavelength of 570nm (orange/red)
Why do we see multitudes of different hues by the use of only 3 color pigments in the cones?
“Recipe book” by whicyh each unique pattern is translated in its own color experience psycholohicall
Why do we see multitudes of different hues by the use of only 3 color pigments in the cones?
“Recipe book” by which each unique pattern is translated in its own color experience psychologically
Opponent Process Theory (p.172)
proposes 3 pairs of color antagonists: red-green, blue-yellow, and white-black
Excitation of neurons sensitive to one member of a pair automatically inhibits neurons sensitive to the other member q
Feature Detectors
neurons in retina/brain (retina’s receptive fields & occipital cortex) that respond to specific attributes of the stimulus, such as movement, orientation etc.
brightness constrast
effect that makes a stimulus LOOK much brighter on a dark background than on a bright one
Lateral Inhibition
activity in one neuron inhibits adjacent neuron’s responses
Hue
attribute that distinguishes blue from red from green; attribute shared by shades of orange
Brightness
dimension of color that differentiates black from white and the various shades of gray in between
Saturation
“purity” of a color ; the extent to which it is chromatic rather than achromatic
cornea
transparent layer forming the front of the eye –focusing vision
iris
responsible for controlling the diameter and size of the pupil (amount of light reaching the retina
pupil
hole located in the center of the iris of the eye that allows light to strike the retina
lens
When you try to focus on something the lens changes shape and then focuses the incoming light onto the retina
Retina
area in the back of the eye that contains rods and cones
