Chapter 3.2 Notes
Chapter 3.2 Notes PSYC 1101
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This 7 page Class Notes was uploaded by Christina Ha on Sunday September 4, 2016. The Class Notes belongs to PSYC 1101 at University of Georgia taught by Kara A. Dyckman in Fall 2016. Since its upload, it has received 108 views. For similar materials see Elementary Psychology in Psychology (PSYC) at University of Georgia.
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Date Created: 09/04/16
9/2/2016 What do we see? Light: electromagnetic energy wave o Fluctuating electric and magnetic fields o Light is fast o No light, no sight Wavelength: the distance between two waves o Different wavelengths correspond to different colors that we perceive o All that is out there in the physical world are different wavelengths of light o As humans, we can only see the “visible light” band o What we see as purple and blue are shorter wavelengths (400 nm) Gamma rays have short wavelengths because they’re on the far left of the spectrum. o What we see as red and orange are longer wavelengths (700 nm) Radio waves have long wavelengths. Features of color Hue: color o Determined by wavelength of light it reflects o Ex: blue, red, green Brightness: intensity of color o Depends on wave height (amplitude: distance from midpoint to peak) o Higher amplitude = higher brightness o Ex: bright blue, duller blue Saturation: how pure the color is o Determined by how constant the wavelength is o Ex: Think of the color red. What color red are you thinking about? There are many different shades of red, which have different wavelengths of light in them. A number of different wavelengths are all combined to create a color. How many different wavelengths are making up this stimulus that you can see? The Human Eye Cornea: clear outer layer over the colored portion of the eye o Shields the eye from damage by dust, bacteria, poking o Focuses incoming light waves o Imperfections in its shape can often lead to blurred vision o LASIK eye surgery: uses a laser to reshape the cornea, leading it to focus the light properly Iris: a muscle that opens and closes, or changes the size of, the pupil Pupil: the black hole in the center of the iris o Ex: When it’s dark in the room: your iris muscles relax, causing your pupil to get bigger/wider. Your pupil getting bigger allows more light to get inside your eye. o Ex: When you’re outside in the bright sun: the iris muscles squeeze, which causes your pupil to constrict. Lens: similar to the cornea, it focuses incoming light Also, the lens changes its shape so it can see images that are near and far (accommodation) o The lens is behind the pupil o Lens is the one that bends the light. It affects how clear your image is. o If you are nearsighted or farsighted, that means your lens is not bending the light properly. Your lens should bend the light so you get a nice image on the other side. Retina Retina: it lines the back of your eye o No retina = no vision o Light waves move through the jellylike filling of the eyes after getting past the cornea, pupil, and lens o Retinopathy of prematurity (ROP): a condition in which blood vessels in the retina grow incorrectly Ex of ROP: Think back to the triplets (Emma, Zoe, and Sophie from chapter 3). Because they were born prematurely, their blood vessels started to branch in an unusual way. In the end, it pulled the retina from the back of the eye. o Retina is responsible for transduction: sensing light, relaying messages to the brain Photoreceptors: absorb light energy and turn it into chemical and electrical signals for the brain to process o After light goes through your entire eye and hits the very back of your eye (your retina), you will reach your photoreceptors o Photoreceptors allow you to take information from the physical world and transmit it o Two types of photoreceptors: Cones and rods (easy to remember because they are shaped like their names) Rods: useful for night vision because it is responsible for sight when the light level is low; not sensitive to color If we only had rods, we would only be able to see black and white Cones: provides color vision and allows us to see fine details (ex: small print on back of a shampoo bottle) o When the light hits them, it transduces this light signal into a neural system and fires an action potential. They synapse into bipolar cells, which synapse onto the ganglion cells. o The collection of axons of the ganglion cells becomes your optic nerve. o Fovea is the place you are looking right now. (precise detail) If you move your eyes, something else is going to be your fovea. Lacks rods and cones are most densely packed here. TRY THIS How do you find your blind spot? Close your left eye. Hold your left thumb out at arm’s length. Put your right thumb next to your right thumb so that they’re touching each other. Keep looking at your left thumb and move your right thumb to the right so that it’s not in your field of view anymore (about six inches to the right?) Side note: Saccades get the object that we want to see in that area on our retina that has really good visual acuity. Your eye movements change fast so that they can jump from one place to another. Coding for objects in our environment Simple stimuli o Feature detectors are actual neurons that code for specific simple stimuli; like the orientation of a line o Ex: If you present a vertical line, there are certain neurons in your brain that will fire very quickly. However, they may not fire a lot for horizontal lines. This is experience dependent. When you’re a baby (which is a critical period to learn types of visual input), you need to be exposed to all these different types of lines in order for your brain to develop these types of neurons to code If you are deprived of some orientation of lines, you will behave differently. Ex: An experiment was done with kittens who were raised with vertical stripes. Because they were only raised with vertical lines, the researchers studied that they could not see or process horizontal lines Complex stimuli (Imagine Oprah Winfrey) o Patterns of activation of different neurons o They allow you to recognize Oprah’s face. You don’t have one neuron in your brain that allows you to recognize your best friend or a famous celebrity. Feature detectors activate your neurons and allows you to perceive different objects or different people in your environment. Color Vision How do wavelengths translate into perception of color? o I call an object red and I have an idea of what this red is. You and I have both been taught to call this color red, but my perception could be different than yours. o Here is where the trichromatic theory and the opponent process theory explain human color vision. Trichromatic theory has three types of cones that correspond to different wavelengths of light: o Red: long wavelength of light; 620700 nanometers (come into your eye, go all the way back to your photoreceptors, and signal the red cones) o Green: medium wavelength of light; 500575 nm o Blue: get excited by short wavelengths of light; 450490 nm o When red, blue, and green light wavelengths are combined in equal proportions, they create a white light. o Any other wavelength of light is a combination of red, green, and/or blue of what color you see. Color deficiency (or color blindness): loss/ damage to one or more of the cone types o Ex: Ishihara Test o Redgreen color defects: 8% of men and less than 1% of women have some degree of color blindness o Afterimage: “an image that appears to linger in your visual field after its stimulus, or source, is gone” Opponentprocess theory: a special group of neurons that respond to opponent colors (blue/yellow, red/green, and black/white) o One neuron fires by the color red, but is inactive when you see green. The other neuron gets excited when you look at green, but is turned off when you look at red. We need both the trichromatic and opponentprocess theories in order to make the different aspects of color vision clear. Color perception takes place in the lightsensing cones in the retina and in the opponent cells serving the brain
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