Psychology: Sensation and Perception
optic nerve
-nerve leading from the retina that carries impulses to the occipital lobe of the brain -the optic nerve is divided into two parts. impulses from the left side of each retina (right visual field) go the left hemisphere and vice versa
brightness constancy
we percieve objects as being a constant color even as the light reflecting off the object changes
signal detection theory
-investigates the effects of the distractions and interference we experience while perceiving the world -takes into account how motivated we are to detect certain stimuli and what we expect to perceive -tries to explain and predict the different perceptual mistakes we make
visible light
-Color is perceived due to a combination of different factors: Light intensity - How much energy the light contains determines how bright the object appears. Light wavelength - The length of light waves determines the particular hue we see. We see different wavelengths within the visible light spectrum as different colors.
constancy
-Every object we see changes minutely from moment to moment due to our changing angle of vision, variations in light, and so on. -Our ability to maintain a constant perception of an object despite these changes. -Several types of constancy: size constancy, shape constancy, and brightness constancy.
color blindness
-Individuals with dichromatic color blindness cannot see either red/green shades or blue/yellow shades. -Those who have monochromatic color blindness see only shades of gray.
Smell (or olfaction)
-Molecules of a substance rise into the air and are drawn into our nose. -The molecules settle in a mucous membrane at the top of each nostril and are absorbed by receptor cells located there. -As many as 100 different types of smell receptors may exist. These receptor cells are linked to the olfactory bulb, which gathers the messages from the olfactory receptor cells and sends this information to the brain. -Nerve fibers from the olfactory bulb connect to the brain at the amygdala and then to the hippocampus, which make up the limbic system, which is responsible for emotional impulses and memory. -This direct connection to the limbic system may explain why smell is such a power trigger for memories.
Taste (or gustation)
-Nerves involved in the chemical senses (taste and smell) respond to chemicals rather than to energy. -Taste buds on the tongue absorb chemicals from the food we eat. -Taste buds are located on papillae, the bumps you can see on your tongue. Taste buds are located all over the tongue and on some parts of the inside of the cheeks and roof of the mouth. -Humans taste five different types of tastes: sweet, salty, sour, bitter, and umami (savory). -People differ in their ability to taste food. The more densely packed the taste buds, the more chemicals are absorbed, and the more intensely the food is tasted. -The flavor of food is actually a combination of taste and smell.
shape constancy
-Objects viewed from different angles will produce different shapes on our retinas, but we know the shape of an object remains constant.
occipital lobe
-location of the visual cortex -part of the brain that processes vision sensations -receives impulses via the optic nerve
depth cues
-Researchers divide the cues that we use the perceive depth into two categories: Monocular cues - Depth cues that do not depend on having two eyes (e.g., linear perspective, interposition, shading, and texture gradient). Binocular cues - Cues that depend on having two eyes (e.g., retinal disparity and convergence).
absolute threshold
-Smallest amount of a stimulus we can detect (50% of the time)
vestibular sense
-Tells us about how our body is oriented in space, three canals in inner ear transmit to brain -when the position of your head changes, the fluid moves in the canals, causing sensors in the canals to move -the movement of these hair cells activate neurons, and their impulses go to the brain
pitch theories
-Theories used to explain how we hear different pitches and tones; -place theory explains that the hair cells in the chola respond to different frequencies of sound based on where they are located in the cochlea -frequency theory: place theory accurately describes how hair cells sense the upper range of pitches but not the lower tones. lower tones are senses by the rate at which the cells fire. we sense pitch because the hair cells fire at different rates in the cochlea
bottom-up processing
-We use only the features of the object itself to build a complete perception. -we start our perception at the bottom with the individual characteristics of the image and put all these characteristics together into our final perceptions. our minds build the picture
perceptual set
-a predisposition or readiness to perceive something in a particular way
trichromatic theory
-a theory of color vision - also called young-helmholtz theory -we have three types of cones in the retina: cones that detect the primary colors of light-blue, red, and green -these cones are activated in different combinations to produce all the colors of the visible spectrum -it cannot explain such visual phenomena as afterimages and color blindness
opponent-process theory
-a theory of color vision -states that the sensory receptors arranged in the retina come in pairs -if one sensory is stimulated, its pair is inhibited from firing, explains afterimages and color blindness
retina
-as the light passes through the lens, the image is flipped upside down and projected on the retina -special neurons in the retina are activated by light and send impulses along the optic nerve to the occipital lobe of the brain
sensory adaptation
-decreasing responsiveness to stimuli due to constant stimulation
vision
-dominant sense in human beings -process: 1. light is reflected off objects 2. reflected lighting coming from the object enters the eye through the cornea and pupil, is focused by the cornea and the lens, and is projected on to the retina where specialized neurons are activated by the different wavelengths of light 3. transduction occurs when light activates the special neurons in the retina and sends impulses along the optic nerve to the occipital lobe of the brain 4. impulses from the left side of each retina (right visual field) go to the left hemisphere and vice versa 5. the visual cortex receives the impulses from the retina, which activate feature detectors for vertical lines, curves, motion, among others
Weber's Law
-ernst weber -the change needed is proportional to the original intensity of the stimulus
gate-control theory
-explains how we experience pain -some pain messages have a higher priority than others. when a high-priority message is sent, the gate swings open for it and shut for low-priority messages, which will not be felt.
lens
-focusses light that enters the pupil -curved and flexible in order to focus the light -as the light passes through it the image is flipped upside down and inverted -the focused inverted image projects on the retina
kinesthetic sense
-gives us feedback about the position and orientation of specific body parts -receptors in our muscles and joints send information to our brain about our limbs -helps us keep track of our body
hearing
-hearing process occurs in several steps: 1. sounds waves, vibrations in the air, travel through the air, and are then collected by our ears 2. sound waves have amplitude and frequency 3. amplitude is the height of the wave and determines the loudness of the sound, which is measured in decibels. 4. frequency, which is measured in megahertz, refers to the length of the waves and determines the pitch 5. vibrations enter the ear and vibrate the eardrum, which connects with three bones in the middle ear: the hammer, the anvil, and the sirrup 6. the vibration is transferred to the oval window, a membrane very similar to the eardrum 7. the oval window membrane is attached to the cochlea, where the process of transduction occurs and neural message are sent to the auditory cortex in the temporal lobe
cocktail party phenomenon
-if you are talking with a friend and someone across the room says your name, your attention will probably involuntarily switch across the room -an example of selective attention
fovea
-indentation at the center of the retina where cones are concentrated -when light is focused onto it, you see it in color -your peripheral vision, especially at the extremes, relies on rods and is mostly in black and white -foveal vision, focusing light on this, results in the sharpest and clearest visual perception
size constancy
-objects closer to our eyes will produce bigger images on our retinas, but we take distance into account in our estimations of size -we keep a constant sizzle in mind for an object and know that it does not grow or shrink in size and it movs closer or farther away
sensation
-occurs when one of our senses (sight, smell, touch, hearing, taste) is activated by something in our environment -occurs before the process of perception (the brain interpreting these sensations)
pupil
-opening in the center of the eye -similar to the shutter of a camera -muscles that control it (called the iris) open it (dilate) to let more light in and also make it smaller to let less light in
Sensory habituation (perceptual adaptation)
-our perception of sensations is partially determined by how used to them we are -when sensory adaptation happens in the sensory organs, this happens in the brain. people who have habituated to something can still perceive it if directed to focus their attention on it.
feature detectors
-perception researchers huber and wiser discovered that groups of neurons in the visual cortex respond to different types of visual images - the visual cortex has these for vertical lines, curves, and motion , among others. what we perceive visually is a combination of these features
cornea
-protective covering on the front of the eye -helps focus light
touch
-sense of touch is activated when our skin is indented, pierced, or experiences a change in temperature -some nerve endings in the skin respond to pressure; others respond to temperature -the brain interprets the amount of indentation as the intensity of the touch -we sense placement of the touch by the place on our body where the nerve endings fire -nerve endings are more concentrated in different parts of our body
chemical senses
-senses of taste and smell -work by gathering chemicals
rods and cones
-special neurons in the retina that are active by light -cones are activated by color -rods respond to black and white and motion
subliminal messages
-stimuli below our absolute threshold -research does not support the claim that subliminal messages affect our behaviors in overt ways
perception
-the brain's interpretation of sensory messages -occurs after the process of sensation -the process of understanding and interpreting sensations
cochlea
-the process of transaction occurs in the cochlea -shaped like a snail's shell and filled with fluid. as sound waves move the fluid, hair cells move. neurons are activated by movement of the hair cells -neural messages are sent to the auditory cortex in the temporal lobe
energy senses
-the senses of vision, hearing, and touch -these senses other energy in the form of light, sound waves, and pressure
difference threshold
-the smallest amount by which two sensory stimuli can differ in order for an individual to perceive them as different. -computed by weber's law -the changed needed is proportional to the original intensity of the stimulus. the more intense the stimulus is, the more it will need to change before we notice a difference
blind spot
-the spot on the retina where the optic nerve leaves the retina and there are no rods or cones -we cannot detect objects in our blind spot, but our brains and the movement of our eyes accommodate for the blind spot, so we usually don't notice it
transduction
-the translation of incoming stimuli into neural signals -neural impulses from the senses travel first to the thalamus and then on to different cortices of the brain -the sense of smell is the one exception to this rule
sound waves
-vibrations in the air, they travel through the air and are collected by our ears. -sounds waves have amplitude and frequency -amplitude is the height of the wave and determines the loudness of the sound, which is measured in decibels. -frequency, which is measured in megahertz, refers to the length of the waves and determines the pitch
top-down processing
-we perceive by filling in gaps in what we sense -occurs when you use your background knowledge to fill in gaps in what you perceive -our experiences creates cheat, mental representations of how we expect the world to be. -schemata can create a perceptual set, which is a predisposition to perceiving something in a certain way
gestalt rules
A set of rules that describe when elements in an image will appear to group together
bipolar cells and ganglion cells
These cells make up different layers in the retina. In the retina, light activates rod and cone cells. Rods and cones send signals to the next layer of cells in the retina: bipolar cells Bipolar cells send signals to the next layer of cells in the retina: Ganglion cells Ganglion cells send signals to the brain through the optic nerve
nerve deafness
occurs when the hair cells in the cochlea have been damaged, usually by loud noise. -in conduction deafness something goes wrong with the system of conducting the sound to the cochlea
