Sensation & Perception: Vision Flashcards
Parts of the Eye
Cornea Pupil Iris Lens Retina
Cornea
The clear, dome-like window in the front of the eye. It gathers and focuses on incoming light.
Pupil
The hole in the iris. It contracts in bright light and focuses on incoming light.
Iris
The colored part of the eye. It has involuntary muscles and autonomic nerve fibers. It also control the size of the pupil, therefore the amount of light entering the eye.
Lens
Lies right behind the iris. It helps control the curvature of the light coming in and can focus near or distant objects on the retina.
Retina
The back of the eye and is filled with neural elements and blood vessels. It detects images.
Duplicity Theory of Vision
The idea that retina have 2 kinds of photoreceptors. Cones and Rods
Cones
A photoreceptor that see color and fine detail. They are most effective in bright light.
Rods
A photoreceptor that do well in low light and black and white images
Fovea
A point in the retina that contains only 1 cone. Moving away from the fovea, there are more rods than cones. You can see detail straight on and peripheral vision is blurrier.
Neurons between the Photoreceptors and the Optic Nerve
Horizontal
Amacrine
Bipolar Cells
Ganglion Cells
Path from Photoreceptors to Optic Nerve
Rods and Cones are respectfully connected to BIpolar Cells and a group of Bipolar Cells are connected to the Ganglion Cells. Layers of Ganglion Cells become the Optic Nerve.
Visual Pathway
- Optic Chiasm
2. Disperse Visual Information
Optic Chiasm
When the nasal fibers (the fibers closest to the nasal) cross paths and the temporal fibers (the fibers closest to the temples) don’t cross paths. Both fibers arrive in different regions of the brain to deliver the information.
Regions of the Brain for Visual Processing
Lateral Geniculate Nucleus of the Thalamus
Visual Cortex of the Occipital Lobe
Superior Colliculus
Hubel & Wiesel
Discovered Feature Detection Theory
Feature Detection Theory
The idea that certain cells in the cortex are maximally sensitive to certain features of stimuli.
3 Different Types of Cells
Simple
Complex
Hypercomplex
Simple Cells
Give information about orientation and boundaries of objects
Complex Cells
Give more advanced information about orientation such as movement
Hypercomplex Cells
Give information about abstract concepts such as object shape.
Single Cell Recording
A research method that involves placing a microelectrode in the cortex so sensitive that it could record responses of a single cell.
Illumination
A physical objective measurement that is simply the amount of light falling on a surface.
Brightness
The subjective impression of the intensity of a light stimuli.
Factors to Measuring Brightness
Adaptation
Simultaneous Brightness Contrast
Dark Adaptation
A type of adaptation where the light “bleached” the rods when entering a dark space. The rod only have one photopigment that must adjust to the darkness.
Rhodopsin
The photopigment in the rods that absorbs a photon of light and becomes bleached. It takes some time before it can adapt to the darkness.
Simultaneous Brightness Contrast
A target area of a particular luminance appears brighter when surrounded by a darker stimulus.
Lateral Inhibition
If a cell is “excited” neighboring cells will inhibit and won’t fire as often. Thus sharpening and highlighting the borders between dark and light.
Color Perception
The wavelength of the light entering the eye.
Subtractive Color Mixture
When we start with light and black is added to create color wavelengths.
Additive Color Mixture
When we start with black and light is added to create color wavelengths
Young-Helmholtz
Created Trichromatic Theory
Trichromatic Theory
The theory that the retina contains 3 different types of cones which are sense to different colors. (Red, Blue, Green) Light hits these cons and creates different colors.
Opponent-Process Theory of Color Vision
The theory that color was interpreted on opposing pairs. (Red-Green + Blue-Yellow + Black-White)
Ewald Hering
Created Opponent-Process Theory of Color Vision
Afterimages
A visual sensation that appears after prolonged or intense exposure to a stimulus. The color of the image will be the opposing color in Hering’s theory.
George Berkley
Identified different cues for depth perception.
Cues of Depth
Interposition Relative Size Linear Perspective Texture Gradients Motion Parallax Binocular Disparity
Interposition
Aka Overlap. When one object cover another, we see the first object.
Relative Size
As an object gets farther away, its image on the retina gets smaller. By using other objects, you can compare the size of the object.
Linear Perspective
When parallel lines appear to converge in the distance.
Texture Gradient
Variations in perceived surface texture as a function of the distance of the observer.
Motion Parallax
When a fixated object outside a moving vehicle seems to move with you
Binocular Disparity
Aka Stereopsis. Each eye has a slightly different scene and when the brain combines these two scenes, we can perceive depth.
Perception of Form
How we abstract perceptual objects by separating the figure from the ground. (Sometimes figure and ground can reverse)
Figure
The integrated visual experience that stands out at the center of attention
Ground
The background against which the figure appears.
Laws of Forming Perception
- Proximity
- Similarity
- Good Continuation
- Closure
- Pragnanz
Law of Proximity
Elements close together tend to be perceived as a unit.
Law of Similarity
Objects that are similar tend to be grouped together.
Law of Good Continuation
Elements that appear to follow in the same direction tend to be grouped together. Tendency to see continuous patterns versus abrupt changes.
Law of Closure
When a space is enclosed by a contour, it tends to be perceived as a figure.
Subjective Contours
A visual illusion that highlights an edge versus color changes against edges. Arise from Law of Good Continuation.
Law of Pragnanz
All perceptual organization will be regular, simple and symmetrical.
Wolfgang Kohler
Created Theory of Isomorphism
Theory of Isomorphism
There is a one-to-one correspondence between the object in the perceptual field and the pattern of stimulation in the brain.
Bottom-Up Processing
The process of collecting the components and summing them up to a pattern based on fixed rules.
Top-Down Processing
The process of using memories and expectations to recognize whole objects and then the components
Different ways to Percieve Motion
Real Motion Apparent Motion Induced Motion Autokinetic Effect Motion Aftereffect
Real Motion
Actually moving the light
Apparent Motion
An illusion that occurs when two dots flashed in different location on a screen seconds apart are perceived as one moving dot.
Induced Motion
The illusion of movement occurring when everything around the spot of light is moved.
Autokinetic Effect
An illusion that occurs when a spot of light appears to more erratically in a dark room , simply because there is not frame of reference.
Motion Aftereffect
When you first view a moving pattern and then view a spot of light; the spot of light appears to move in the opposite direction.
