Psych Notes Chapter 3

• - our eyes can only respond to visible light waves a band called the visible spectrum
• - shortest-violet longest- red
• - ROY G BIV

• - 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"

• - 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

• - 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

• - 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)

• - 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

• - 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.

- however, we see the whole images because the primary visual cortex takes these pieces, combines them into & assembles them whole visual images

• - 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)

• - 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.

• - 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.

• - 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

• - 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

• - 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

• - 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

• - 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

• - 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

• - 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

• - 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

• - 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

• - 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

• - 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

- what we expect to perceive determines, to a large extent, what we actually see, hear, feel, taste, & smell. these are based on prior knowledge

• - 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

• - 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.