Sensation and perception: Taste and hearing
phi phenomenon
-Similar to stroboscopic movement -a series of lights are flashed on and off in quick succession and this creates the illusion that the light appears to move continuously.
Color constancy
-we need to compare the wavelengths of light reflected from the object with those reflected from its background.
Illusory contours
-we sometimes perceive contours and cues to depth even though they do not exist -see document for picture
closure
-we tend to complete figures even when gaps exist -See document for picture
Principle of similarity
-we tend to group figures according to how closely they resemble each other, whether in shape, color, or orientation -See document for picture
Dogs vs. Humans
- Dogs can have 100x more ORNs than humans, making them better at differentiating between different odors -Humans can detect smells in very small quantities
Linear Perspective
-Seemingly parallel lines appear to converge in the distance
Top down influences on smell
-Previous experiences with an odor determine how we respond to it -Same odor is ranked as better when associated with "cheddar cheese" vs. "Body odor" -fMRI shows that brain regions associated with coding the pleasantness of an experience reacted more strongly with "cheddar cheese"
Kinesthetic Sense
-Sense that are in joints, tendons, bones, inner ear and skin called proprioceptors -Provide info about the movement and position of your body in space
Motion Paralax
- the relative movement of objects that are at various distances from the observer -When driving, near by objects pass quickly, while farther away objects pass slowly -If you fixate on an object far away, it seems to match your speed -If you focus on something at an immediate distance, everything before that seems to move in the opposite direction as you. anything farther than that object, moves in the same direction as you.
Lightness constancy
- we need to compare the wavelengths of light reflected from the object with those reflected from its background.
Shape constancy
- we need to know from what angle we are seeing the object
Size constancy
- we need to know how far away the object is from us.
Occlusion
-A near object occludes (blocks) an object that is far away
Motion Cues for Depth perception
-Another clue for depth -Motion Paralax -Motion cues such as these help the brain calculate which objects are closer and which are farther away.
Texture Gradient
-As a uniformly textured surface recedes, its texture continuously becomes denser.
Examples of Binocular depth clues
-Binocular disparity (Aka retinal Disparity) -Convergence
Binocular disparity (aka retinal disparity)
-Caused by the distance between our two eyes -Each eye has a slightly different view of the world, so our brain has access to two different, but overlapping, retinal views -brain uses the disparity between the two retinal images to compute distances to nearby objects -If the disparity is large, the object is close to you
Pathway of scents
-Countless substances release odors into the air, some of these odorant molecules reach our noses -top of nasal cavity has a mucus membrane called the olfactory epithelium -this membrane contains about 10 million olfactory receptor neurons (ORNs) -Odorant molecules bind to these neurons, if enough binding occurs, action potentials are sent to the olfactory nerve -ORN are replaced every 30-60 days -Each ORN has specific receptors that bind to some odorants and not to others -Groups of ORNs send their axons from the Olfactory epithelium to the olfactory bulb -humans have 350 different 0RN types that let us sense about 10000 different smells -ORNs are very sensitive, some of what we sense is actually pain
ESP
-Extra sensory perception -Telekinesis: moving objects with one's mind -Precognition: Seeing/predicting future events -Clairvoyance: Feeling distant events -Telepathy: mind to mind communication
Relative size
-Far-off objects project a smaller retinal image than close objects do, if the far-off and close objects are the same physical size
Ronal Melzack and Patrick Hall
-Gate control theory of pain -The spinal cord contains small, fast nerve fibers that conduct pain signals to the brain -Also has large, slow fibers that carry all other tactile sensations to brain -There is a neurological gate and when tissue is injured, the small, fast, fibers activate and open the gate, and you feel pain -Large fiber activity closes this gate, however, and thus blocks pain signal from reaching the brain. -one way to treat pain is to stimulate "gate-closing" activity -The "gate" appears to be the periaqueductal gray in the brain stem -Pain is perceived in the brain at the anterior cingulate cortex
Gestalt Psychologists
-Gestalt principle: perception is more than just the result of accumulating sensory information -German word "gestalt" means shape/object -In psychology, gestalt means "Organized whole" -Founders of Gestalt psychology had a series of laws about how brain groups the perceived features of a visual scene into organized wholes. - brains use innate principles to organize sensory information. -This is why we see "car" instead of "metal, wheels, doors, etc." -For us, an object exists as a unit, not a collection of features -One of the visual perception system's most basic organizing principles is distinguishing between figure and ground.
Smell and Social behavior
-Humans and other animals can detect odors from pheromones -parents (especially mothers) can tell the smell of their children from other children -Infant can tell the smell of mother's breast from other mother -Also play a role in reproduction in many animals
Pain
-Nociceptors: pain receptors -how we respond to pain is influenced by many factors -For example, when we are distracted from the source of pain, our perception of the pain decreases -How other people respond to our pain -People tend to experience more pain if they are around other people who are experiencing pain -We seem to edit our memory of pain: People overlook a pain's duration and instead focus on the moment of peak pain
Examples of Pictorial/monocular depth clues
-Occlusion -Relative Size -Familiar size -Linear Perspective -Texture Gradient
Smell
-Olfaction -least understood sense, and the only one directly connected to the forebrain (pathways into the frontal lobe, amygdala, and other forebrain structures) -smell has a close relationship with emotion and social areas
Brain
-Olfactory bulb sends into to different parts of the brain, including parts that are important for things like memory and and emotions -This is why smell can have such an immediate pos/neg effect on us -Sensory adaptation causes a very strong smell to fade after a few minutes
Perceptual Organization
-Optical illusions are used to study how brain takes in visual info about an object, and how it is organized -Perceptual psychologists believe that illusions reveal the mechanisms that help our visual systems determine the size and distance of objects in the visual environment.
Structure of tongue
-Papillae: small bumps that cover the top and sides of the -tongue -Inside papillae are hundreds of taste buds -average human has 5000 and 10000 taste buds evenly distributed over the tongue, roof of the mouth, and upper throat. -each taste bud has 50-100 taste receptor cells -some will respond most strongly to sweet tasting molecules, some to salty, some to sour, some to bitter, and some to umami -microvilli: tips of taste receptor cells, react with tastant molecules in food
Size Perception Depends on Distance Perception
-Size of objects retinal image depends on the objects distance from the observer -Farther away an object is, the smaller the image -Most of the time, enough depth information is available for the visual system to work out the object's distance and thus infer how large the object is -Sometimes, though it fails, and an objects appears bigger or smaller than it actually is
Equilibrium and Orientation
-To the upper left of the cochlea is the vestibule that is filled with perilymph -Suspended in this perilymph are two sacs called saccule and utricle -These sacs contain equilibrium receptor regions called maculae -They respond to the pull of gravity and report (via vestibular nerve) on changes in head position -Projecting out of the back of the vestibule are semicircular canals (3 of them) -W/in each canal is a semicircular duct -at the end of each duct is an equilibrium regulator region known as a crista (cristae is plural) -The cristae respond to rotational movements of the head
Motion perception has internal and external cues
-We have neurons specialized for perceiving motion -These neurons will fire when movement occurs -Motion aftereffects show that these neurons exist -visual cortex has neurons that respond to movement in a given direction -When you stare at a moving object long enough, neurons adapt to motion and get fatigued -if stimulus is suddenly removed, motion detectors that respond to other types of movement are more activated than fatigued motion detectors -thus, object seems to move in a different direction -this is the waterfall effect
Familiar size
-We know how large familiar objects are, so we can tell how far away they are by the size of their retinal images
Olfactory bulb
-a brain structure located above the nasal cavity beneath the frontal lobes -axons of all ORNs of a particular type meet at a location called the glomerulus -Humans have about 350 glomeruli -different odorants can have varying levels of effect on different glomeruli
Binocular depth clues
-available from both eyes together -useful for objects only relatively close to us
monocular depth clues
-available from each eye alone -Can still perceive depth even though we only have one eye -Also Called pictorial depth clues
Perceptual constancy
-brain correctly perceives objects as constant despite sensory data that could lead it to think otherwise -Example: reflexion in mirror is smaller than the objects being reflected -For the most part, changing the object's angle, distance, or illumination does not change our perception of that object's size, shape, color, or lightness -to perceive any of these four constancies, we need to understand the relationship between the object and at least one other factor. - In each case, the brain computes a ratio based on the relative magnitude rather than relying on each sensation's absolute magnitude -these constancies illustrate that perceptual systems are tuned to detect changes from baseline conditions, not just respond to sensory inputs.
Taste
-gustatory sense - once thought to be sweet, sour, salty, and bitter with all other flavors stemming from mixtures of these four -discovered a fifth taste: savory meat taste of umami -Umami is best experienced with the flavor enhancer MSG -important for more than just pleasure, taste also attracted our ancestors to protein rich food that helped them survive -bitter foods were avoided, prevented toxic plants. -both smell and taste work together to produce flavor, which we call sensory interaction
Tastant molecules
-how taste receptors react is determined by the tastant molecules -Taste receptors that respond most strongly to saltiness (the presence of sodium ions) and sourness (the presence of hydrogen ions) are depolarized by these ions -Umami: glutamate binds to sodium ion channels which thereby opens these channels allowing an influx of sodium ions (and a depolarized state) -bitter substances: the bitter substance will bind to potassium ion channels and close them (thereby depolarizing the cell) -sweetness: sugar molecules bind to receptor proteins on taste receptors which results in depolarization.
Optical illusions
-in any figure, the brain assigns something to be the figure, and the rest of the scene to the background
Depth Perception is important for locating objects
-one of the visual systems most important tasks is to locate objects in space -How can we construct a 3D visual representation of the world from 2D retinal input? -Visual system perceives depth in both the world around us, and in pictures, videos etc. -there are two types clues that help us perceive depth: Binocular and monocular depth clues
Stroboscopic movement
-perceptual illusion that occurs when two or more slightly different images are presented in rapid succession
Convergence
-refers to the way that our eye muscles turn our eyes inward when we view nearby objects -the brain knows how much the eyes are converging and it uses this information to perceive distance.
Pheromones and Reproduction
-researcher used a PET scan to study brain's response to two orders: testosterone in men's sweat, and estrogen in women's urine -Testosterone activated hypothalamus in hetero women, but not hetero men -Estrogen activated hypothalamus in hetero men but not women -homosexual men responded to odors the same way that women did -lesbians were closer to men's response -Other common odors unrelated to sexual arousal were processed similarly by all three groups.
Taste as a chemical sense
-taste receptors are chemoreceptors that detect different molecular combinations in foods and liquids -sight and hearing are often called energy senses, it is energy being converted to neural messages (light waves and sound waves)
Taste perception
-taste will fade with age -taste receptors reproduce themselves about every two weeks -Tasters: report a mild sensation of extreme taste in a food (50% of people) -Supertaster: report a extreme sensation of an extreme taste in a food (25% of people) -Nontaster: report no sensation of an extreme taste in a food (25% of people) -Children are all either tasters or supertasters, which could explain their fussiness with food
Principle of Proximity
-the closer two figures are to each other, the more likely we are to group them and see them as part of the same object. -See document for picture
Good continuation
-the tendency to interpret intersecting lines as continuous rather than as changing direction radically -See document for picture
How does brain know whats moving?
-why when you move your head, objects dont just jump around? -the brain calculates an object's perceived movements by monitoring the movement of the eyes, and perhaps also of the head, as they track a moving object. -Also, motion detectors track an image's motion across the retina, as the receptors in the retina fire one after another.
Two pathways that smell can follow in the brain
1: Travels by the thalamus to the olfactory cortex (temporal lobe) and part of the frontal lobe known as the orbitofrontal cortex (where smells are consciously identified and and interpreted.) 2. Bypasses the thalamus and flows directly to the hypothalamus, amygdala and other regions of the limbic system
Two major principles of the gestalt theory
Principle of proximity and the principle of similarity -These two theories show that we tend to cluster elements of the visual scene -Clustering enables us to consider a scene as a whole rather than as individual parts.
stereoscopic vision
The ability to determine an object's depth based on that object's projections to each eye -goes with Binocular disparity
Touch
Two types of skin: Hairy skin and glabrous skin -Hairy skin: contains hair cells -Glabrous skin: No hair cells, very sensitive, located on fingertips, lips, palms of hands -Our sense of touch is a mixture of 4 types of specialized receptors: pressure, cold, warmth and pain
Pheromones
biochemical odorants emitted by other members of its species that can affect the animal's behavior or physiology.
