Vision
Our eyes receive light energy and __________ it into neural messages that our brain processes into what we consciously see. transduces
Light Energy When we look at things, we actually see the light reflected off of them. Visible light is a thin slice of the whole spectrum of electromagnetic energy.
Light and sound use similar descriptive language because both have properties of waves: ● wavelength ● amplitude (hue or color) (intensity)
The Structure of the Eye
The Structure of the Eye Cornea = outer covering of the eye.
The Structure of the Eye Pupil = the adjustable opening in the center of the eye through which light enters.
The Structure of the Eye Iris = a ring of muscle tissue that forms the colored portion of the eye around the pupil and controls the size of the pupil opening. The iris dilates/constricts in response to changing light intensity
The Structure of the Eye Lens = the transparent structure behind the pupil that changes shape to help focus images on the retina.
The Structure of the Eye Retina = the light-sensitive inner surface of the eye, containing the receptor rods and cones plus layers of neurons that begin the processing of visual information.
The Structure of the Eye Blind Spot = the point at which the optic nerve leaves the eye, creating a “blind” spot because no receptor cells are located there.
The Structure of the Eye Fovea = the central focal point in the retina, around which the eye’s cones cluster.
The Structure of the Eye Let’s take a closer look at the Retina!! Optic Nerve = the nerve that carries neural impulses from the eye to the brain.
The Retina’s Receptor Cells Rods Detect black, white, and gray; necessary for peripheral and twilight vision. Cones Concentrated near the center of the retina and function in daylight or in well-lit conditions. The cones detect fine detail and give rise to color sensations.
The Retina’s Receptor Cells Rods Cones
The Retina’s Receptor Cells
The Retina’s Reaction to Light
Eyes are important organs in your sight process, but you see as much with your _____ as you do your eyes! brain
Visual Information Processing Feature Detector Cells Specialized neurons in the brain that respond to specific features, such as shape, angle, or movement. Get their name from the ability to respond to specific features Pass information to teams of cells (supercell clusters) that respond to specific features.
fMRI scans show different activation areas. Research indicates we have a “vast visual encyclopedia” of specialized cells that respond to one type of stimulus.
Visual Information Processing Parallel Processing: the brain divides stimuli into subdivisions Motion Form Depth Color The brain processes these in separate cortex areas, then our perceptions are formed by them being integrated together.
Movement Video https://www.youtube.com/watch?v=9fBjNYKT0NY
Parallel Processing: the brain divides stimuli into subdivisions
Parallel Processing: the brain divides stimuli into subdivisions
Parallel Processing: the brain divides stimuli into subdivisions
Parallel Processing: the brain divides stimuli into subdivisions
Parallel Processing: the brain divides stimuli into subdivisions
A simplified summary of visual information processing Retinal Processing: Receptor rods and cones: transduction Feature Detection: Brain’s detector cells respond to specific features – edges, lines, angles Scene Parallel Processing: Brain cell teams process combined information about motion, form, depth, color Recognition: Brain interprets the constructed image based on information from stored images
Assignment: Complete the Eye handout It is due Monday and there will be a quiz over its parts then. P. 82 in Blue Psy-1 book P. 172-173 in Green AP Psy book
Vision Perception
A true “optical” illusion
Subjective Contours Source: Gaetano Kanizsa
R. C. James Photograph
Necker Cube
Necker Cube
Necker Cube
Necker Cube
Subjective Necker Cube
Hermann Grid
The Scintillation Grid: Bernd Lingelbach
Color Vision
Color Vision Young-Helmholtz Trichromatic theory Theory that the retina has three different color receptors: red, green, and blue.
Color-Deficient People Most are not truly “colorblind” Lack functioning in red or green sensitive cones (sometimes both) Their vision is monochromatic or dichromatic instead of trichromatic.
This is how fall foliage looks to a colorblind person. This is how fall foliage looks to everyone else.
Red/Green Color blindness
Color-Deficient People Here is a video of a guy seeing color for the first time in his life with the assistance of EnChroma glasses.
Color Vision Why can people who are blind to red and green see yellow? Opponent-Process theory Theory that vision has four primary colors arranged in pairs: red and green, blue and yellow, (black & white) If one in the pair is stimulated, the other cannot be working.
Stare at the white dot for 30 seconds
Which theory is correct? Probably both are correct. Two-stage color processing RGB cones respond to different stimuli These signals then processed by the nervous system’s opponent-process cells.