Sensation & Perception Flashcards
Difference threshold
The amount of stimulus energy that needs to be added to or subtracted from a stimulus for a person to say that she notices a difference
Absolute threshold
The amount of stimulus energy needed for a person to say that she perceives it.
JND
One jnd needs to be added to or subtracted from a stimulus for a person to say that she notices the difference.
Weber’s law
What’s important in producing a jnd is not the absolute difference btw the 2 stimuli, but the ratio of them. Fechner.
Fechner’s law
Relates the intensity of the stimulus to the intensity of the sensation. Sensation increases more slowly as intensity increases
Steven’s power law
Also relates intensity of stimulus to intensity of sensation. Stevens performed some experiments that did not fit w fechner’s law, but instead fit this equation.
Response bias
Measures how risky the subject is in sensory decision making; based upon nonsensory factors
Sensitivity
Measures how well the subject can sense the stimulus
ROC curve
Used to graphically summarize a subject’s responses in a signal detection experiment. John A. Swets refined the use of ROC curves
Signal detection theory
Gives us a way to measure both sensitivity and response bias. Hit, miss, false alarm and correct rejection
Commonalities of sensory systems
Receptors- respond to physical stimuli
Transduction- translates physical energy to neural impulses
Projection areas- brain areas that further analyze sensory input
Cornea
Clear, domelike window in the front of your eye which gathers & focuses the incoming light
Pupil
The hole in the iris. Contracts and dilates in bright & dim light
Iris
The colored part of the eye. Involuntary muscles. It controls the size of the pupil, and therefore, the amount of light that enters the eye
Lens
Lies right behind the iris. Helps control the curvature of the light coming in and can focus near or distant objects on the retina
Retina
In the back of the eye & is like a projection screen that detects images. Image appears upside down on Retina
Duplicity theory of vision
States that the retina contains two kinds of photoreceptors- rods & cones (light must first pass through intermediate sensory neurons b4 reaching photoreceptors).
Cones
Used to detect fine detail & color vision. Most effective in bright light. In the center of the eye is the fovea- contains only cones. As you move away from center, # of cones decrease
Rods
Fxn best in dim light & only perceive achromatic colors. Not involved in color, low sensitivity to detail. More Rods than cones, at periphery, only rods
Connection btw receptors and optic nerve
Rods & cones➡️bipolar neurons ➡️ganglion cells (form optic nerve). The greater the number of receptors that converge onto one ganglion cell, the more difficult it is to see fine detail
Optic chiasm
Here the fibers from the nasal half of the retina cross paths. The fibers from the temporal halves do not cross paths on way to brain.
Where visual info goes when it leaves brain
Lateral geniculate nucleus of the thalamus, the visual cortex in the occipital lobe, and the superior colliculus.
Hubel & Wiesel work on visual cortex
Feature detection theory. Certain cells are maximally sensitive to certain stimuli: simple- orientation, complex- movement, and hypercomplex- shape
Brightness perception
Illumination- objective measurement of light.
Brightness- subjective impression of intensity
Dark adaptation
Caused by the regeneration of rhodopsin, the photopigment in the rods
Lateral inhibition
Adjacent retinal cells inhibit one another; sharpens and highlights borders between light and dark areas
Subtractive color mixture
Occurs when we mix pigments. Blue + yellow make green
Additive color mixing
Occurs when we mix lights. Primary colors are blue, green (not yellow) & red. Red + green= yellow
Young-Helmholtz (trichromatic)
Three types of color receptors that are differentially sensitive to primary colors red, blue, green. Research has shown this theory to be the correct one
Hering (opponent process)
Three opposing pairs: red- green, blue-yellow, black-white. The concept of afterimages led him to his theory.
Interposition (overlap)
When an object covers another object, we see it as being in front. George berekley
Relative size
Another cue for depth perception. If u know something about actual size, u can tell how far away something is by how large it appears.
Linear perspective
Refers to the convergence of parallel lines in the distance
J.J Gibson
Texture gradients. As scene recedes from viewer, the surface texture appears to change.
Motion parallax
Looking out a car window. Speed at which objects appear to move. Kinetic depth effect- when an object rather than the perceiver moves, the motion gives us cues about relative depth