Psych Notes Chapter 3

  1. Vision
    • - our eyes can only respond to visible light waves a band called the visible spectrum
    • - shortest-violet longest- red
    • - ROY G BIV
  2. The Eye
    • - about 1 inch in diameter
    • - cornea- transparent, protective cover
    • - bends light rays inward, directing i through the pupil
    • - the iris dilates & contracts the pupil to regulate the amount of light entering the eye
    • - just behind the iris & the pupil is the lens
    • - composed of many thick layers, it looks like a transparent disc
    • - the lens focuses on viewed objects
    • - it flattens as it focuses on close objects (AKA accomadation)
    • - by about age 40, the lens loses its ability to change its shape to accomodate for near vision (AKA presbyopia) "old eyes"
  3. From Lens to Retina
    • - the lens focuses objects on the retina
    • - projected upside down & reversed left to right
    • - the image (from lens to retina) can be projected too short or long
    • - nearsightedness (myopia)- when the lens focuses images of distant objects in front of rather than on the retina. near objects are clear, but far ones are blurry
    • - farsightedness (hyperopia)- occurs when the lens focuses objects behind, rather than on the retina. far objects are clear, but close objects are blurry.
    • - at the center of the retina is the fovea
    • - about the size of a (.)
    • - images are focused on the center of your fovea. it has no rods but about 30,000 cones packed tightly together. it provides the clearest sharpest vision in the whole retina
  4. The Rods & Cones
    • - located at the back of the retina
    • - light sensitive 120 million rods, 6 million cones in each retina
    • - the cones allow us to see color & fine detail in adequate light. they dont function well in dim light
  5. From Retina to the Brain
    • - rods & cones transduce or change light waves to neural impulses
    • - about 1 million axons lead from the wall of the retina to the brain
    • - there are no rods & cones where the cable runs through the retinal wall (AKA blind spot)
  6. Vision and the Brain
    • - beyond the retinal wall is the optic nerve
    • - the two optic nerves come together (AKA optic chiasm)
    • - this plays a role in depth perception
    • - from the optic chiasm, the optic nerve fibers extend to the thalamus & transmit impulses to the primary visual cortex
  7. The Primary Visual Cortex
    • - part of the brain where visual information is processed
    • - through research we have discovered that feature detectors (coded at birth)
    • - these are some neurons that respond to certain patterns. some respond to only lines & angles, while others respond to vertical or horizontal lines.
  8. The Primary Cortex
    - however, we see the whole images because the primary visual cortex takes these pieces, combines them into & assembles them whole visual images
  9. Color Vision
    • - 3 dimensions of light combine to provide us with color
    • - they are: hue ( the specific color perceived), saturation (the purity of color), & brightness (the intensity of the light energy)
  10. Theories of Color Vision
    • - trichromatic theory- thomas young (1802)
    • - there are 3 kinds of cones in the retina that respond (sensitive to) to blue, green, & red)
    • - opponent-process theory- Ewald Hering in 1878
    • - 3 kinds of cells respond by increasing or decreasing their rate of firing when different colors are present. Red/green, yellow/blue, & white
    • - afterimage- stare at a color & then stare at a white object. the negative will remain. both theories are correct in a way.
  11. Color Blindness
    • - the inability to distinguish certain colors from one another
    • - about 7 % of males & > 1% of femals suffer from color blindness
    • - a person can have degrees of CB
    • - people with normal color vision, the X chromosome may have as amny as 9 genes for color perception. others may have as few as 2.
  12. The Absolute & Difference Thresholds
    • - absolute threshold- the difference between not being able to perceive something & just barely able to perceive it
    • - the minimum is 50% of the time
    • - the difference threshold is the measure of the smallest increase or decrease in the physical stimulus that is required to produce the JND
    • - Ernst Weber- stated that the JND depended on a % of change in a stimulus rather that a fixed amount
    • - the threshold is different for the senses
    • - a 20% difference is needed for taste
  13. Transduction & Adaption
    • - we do not actually see with our eyes or hear wiht our ears. these sense organs are only the beginning. sensations are completed in the brain.
    • - to get the "messages" to your brain, your sense organs have highly specialized cells called sensory receptors. they respond to light, odor, etc.
    • - the process of converting sensory information into neural impulses
    • - we experience a sensation only when the appropriate part of the brain is stimulated
    • - over time, we "get used to" certain levels of stimuli (AKA sensory adaptation)
    • - SA allows us to shift attention to stronger stimuli
  14. The Mechanics of Smell
    • - the human olfactory system can distinguish between 10,000 different smells
    • - you cant smell a substance unless some of its molecules vaporize
    • - olfactory epithelium- (2) 1 in. patches of tissue at the top of each nasal cavity
    • - contains 10 million neurons
    • - the intesnity of the smell stimulus depends on how many olfactory neurons are firing at the same time
    • - dogs have about 20 times more than the amount of olfactory receptors that humans do
    • - olfactory neurons are different from other neurons. they both come into direct contact with sensory stimuli & reach directly into the brain.
    • - they function for about 60 days, die & are replaced by new cells
    • - olfactory neurons fire a smell message directly to the olfactory bulb (just above the nasal cavities)
    • - signal is sent to the thalamus & orbitofrontal cortex & then sent to other parts of the brain
    • - the process of sensing odors is the same in every individual, but some are more sensitive to smell than others
    • - young people are more sensitive then older people
    • - nonsmokers are more sensitive than smokers
  15. Smell & Memory
    • - smell can trigger emotions
    • - the olfactory system sends info to the limbic system (an area of the brain that contains emotions & memories), but bypasses the hippocampus (involved in most of our memories)
    • - in older people, the greater loss of olfaction, the greater chance of dimentia
    • - preventing a loss of smell will not prevent dementia
  16. Pheromones
    • - most animals excrete pheromones- to mark territory or to signal sexual receptivity
    • - humans produce androsterone- it can affect heart rate & mood.
    • - research has shown that humans, although not consciously aware of it, respond to pheromones when it comes to mating
  17. Touch
    • - your skin is your largest organ
    • - tactile info is sent to your brain when an object touches or depresses the skin
    • - touch receptors are sent through the skin to the spinal cord reaching the somasensory cortex
  18. Pain
    • - 1. motivates us to tend to injuries
    • 2. restrict activities
    • 3. seek medical help
    • 4. teaches us to avoid pain-producing situations
    • - chronic pain- lasting 3 months or more is felt by 34 million americans
    • - 3 most common types:
    • - low back pain, headache, & arthritis pain
    • - gate-control theory- an area in the spinal cord that acts like a "gate." it can block or send pain messages to the brain
    • - you feel pain only when pain messages are carried by slow-conducting nerve fibers thus causing the "gate" to open.
    • - it also blocks large, fast-conducting nerve fibers that can block nerve fibers
    • - when you are hurt, your often rub/apply gentle pressure to the area, thus stimulating large, fast-conducting nerve fibers & blocking some slow-conducting nerve fibers
  19. Psychological & Cultural Influences on the Experience of Pain
    • - pain has both physical & emotional components & can vary from person to person
    • - people feel the most pain when they have negative thoughts about it, fear its potential threat to their wellbeing & express feelings of helplessness
  20. Endorphins
    • - americans spend more money on pain relief than on any other medical purpose
    • - over $40 billion a year
    • - endorphins are released naturally ( which block pain) when you are injured, experience stress, or extreme pain, laugh, cry, or exercise
  21. Prior Knowledge
    • - the knowledge we possess about a given sensory stimulus influences how we perceive it
    • - prior knowledge can sometimes enhance perception, but it can lead to errors as well
  22. Bottom-Up & Top-Down Processing
    • - bottom-up processing- taking prior knowledge & using it to make sense of something new/unknown. In other words, taking individual parts & finding patterns to make sense of the information
    • - top-down proceesing- previous experience & perceptual knowledge are applied to recognize the nature of a "whole" & then logically deduce the individual components of that whole
  23. Perceptual Set
    - what we expect to perceive determines, to a large extent, what we actually see, hear, feel, taste, & smell. these are based on prior knowledge
  24. Attention
    • - inattention blindness- its hard for our eyes to keep track of many moving objects at the same time
    • - even though we see changes, we do not always perceive them
  25. Social Perception
    • - research indicates that when judging motion based on conflicting auditory & visual input, people rely on auditory input.
    • - in the case of social perception, the opposite is true. visual clues often take priority over auditory cues.
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Psych Notes Chapter 3
psych ch3 notes