Sensation and Perception Flashcards
Define sensation
The feeling that results from physical stimulation
Define perception
The way we organize and experience sensation
Define the three steps of sensation
- Reception - takes place when receptors for a particular sense detects a stimulus
- Transduction - process in which physical sensation is changed into electrical messages that the brain can understand
- Transmission - sends neural information to the brain
What is the receptive field?
Distinct region of sensory space that can produce a response when stimulated; these are found on the body surface and in the muscles, joints, eyes, and internal organs
Name the theories of perception
- Nativist theory
- Empiricist theory
- Structuralist theory
- Gestalt psychology
Define Nativist Theory
Asserts that perception and cognition are largely innate and generally based
- Humans are born with all of their perceptual capacities, even though some abilities are not present at birth and develops during maturation
Define Empiricist Theory
Perception is basically learned and develops as the individual adapts to their environment
Define Structuralist Theory
Perception is the sum total of sensory input; one can understand the mind by understanding its basic components
-focuses on bottom-up processing
What is bottom-up processing?
Starts with sensory data and works upward to the brain’s integration of that data
What is Gestalt Psychology?
Asserts that people tend to see the world in terms of organized wholes rather than constituent parts
-focuses on top-down processing
What is top-down processing?
Starts with higher level cognitive processes and works downward to sensory information
Define absolute threshold and provide an example
Minimum amount of a stimulus that can be detected 50% of the time
-Lowest pitch sound a human can hear
Define differential threshold
(also known as just noticeable difference)
Minimum difference that must occur between two stimuli in order for them to be perceived as having different intensities
Who defined differential threshold?
E.H Weber
Define terminal threshold and provide an example
Upper limit above which the stimuli can no longer be perceived
- Highest pitch sound a human can hear
What is psychophysics?
The study of the quantitative relations between psychological sensation and physical stimuli
Who coined the term psychophysics?
Gustav Fechner
Define Weber’s Law and provide its formula
Applies to all senses but only to a limited range of intensities; Law states that a stimulus needs to be increased by a contact fraction of its original value in order to be perceived as noticeably different
K (constant fraction) = delta I (increase in intensity needed for JND)/ I (original intensity)
Define Fechner’s Law and provide its formula
Built on Weber’s Law; States that the strength of a stimulus must be significantly increased to produce a slight difference in sensation
S (sensation strength) = k log R (logarithm of original intensity)
Define J.A. Swet’s Theory of Signal Detection (TSD)
Subjects detect stimuli not only because they can but because they want to. Factors motivation into the picture (might explain inconsistent responses)
-example of response bias
Define the different types of responses (interplay between response bias and stimulus intensity)
-false alarm: saying that you detect a response that is not there
-hit: correctly sensing a stimulus
-miss: failing to detect a present stimulus
-correct rejection: rightly stating that no stimulus exists
What are ROC curves?
graphical representation of a subject’s sensitivity to a stimulus
What is light composed of?
photons and waves
Define hue
(also known as color)
dominant wavelength of light
Define brightness
physical intensity
What is the cornea?
Clear protective coating on the outside of the eye
Where is the lens located?
Behind the cornea
What allows the lens to bend (accommodate)?
Ciliary muscles
What is the role of the lens?
Bends to focus an image of the outside world onto the retina?
What is the role of the retina?
Receives light images from the lens
Where is the retina located and what is it comprised of?
In the back of the eye; ~132 million photoreceptor cells and other cell layers that process information
What are receptor cells (rods and cones) responsible for?
Cells on the retina are responsible for sensory transduction; happens through chemical alteration of photopigments
What is the role of rods and where are they primarily located?
Particularly sensitive to dim light and are used for night vision; concentrated along sides of the retina - super important for peripheral vision
What is the role of cones and where are they primarily located?
Particularly sensitive to color and daylight vision; concentrated in the fovea (center of retina with greatest visual acuity)
What does visual acuity mean?
Seeing fine details
Why do cones see better than rods?
There are fewer cones per ganglion cell than rods per ganglion cell
Describe the pathway after light passes through its receptors
It travels through horizontal cells to the bipolar cells to the amacrine cells; some information processing takes place here; finally information goes to the ganglion cells (make up the optic nerve)
What cells make up the optic nerve?
ganglion cells
List the different theories for details of vision
- Opponent-color (opponent-process)
- Trichromatic theory (component theory)
Define the opponent-color (process) theory
Proposed by Ewald Hering; Suggests that two types of color sensitive cells exist: cones that respond to blue-yellow colors and cones that respond to red-green. When one color of the pair is stimulated, the other is inhibited.
(Ex: if object appears red, the green is inhibited - why we see afterimages)
What theory of vision explains afterimages?
Opponent-process
Describe the trichromatic theory of vision
Proposed by Thomas Young and Hermann von Helmholz; Suggests that there are three types of receptors in the retina: cones that respond to red, blue, or green
