Unit 3 Psychology Sensation and Perception PDF

Preview

Summary

Sensation, Perception, Processing (Top up/bottom down), Subliminal Stimuli, light spectrum, anatomy of the eye, Kinesthetic and vestibular senses,...

Description

Unit 3: Sensation and Perception Sensation: Occurs when special receptors in the sense organs (eyes, ears, nose, skin, taste buds) are activated, allowing various forms of outside stimuli to become neural signals in the brain. (sensory information is detected by a sensory receptor neuron) Perception: The method by which the brain takes all of the sensations that a person experiences at any given moment and allows them to be interpreted in some meaningful fashion. (the way we organize, interpret, and consciously experience sensory information) • Bottom-Up Processing: perceptions are built from sensory input. • Top-Down Processing: how we interpret sensations is influenced by our available knowledge, our experiences, and our thoughts Example: you see a smelly homeless man, you think “ew, he needs a bath, gross” (bottom up processing) on the other hand, if you see someone that is smelly and homeless but you know that they are smelly and homeless because they lost their job, you feel bad for them. This is top down because it is influenced by your experience and available knowledge (you know the person) • Perception is affected by: Attention: Failure to notice something that is completely visible because of a lack of attention is called inattentional blindness. Motivation: The ability to identify a stimulus when it is embedded in a distracting background is called signal detection theory, an example is when you’re waiting for a phone call and hear the ringing over the loudness of the shower • Perceptions can be affected by differences in the types of environmental features experienced on a regular basis by people in a given cultural context People in western cultures perceive buildings as having straight lines People in non western cultures like Africa, where they have huts in circles, do not perceive buildings as straight lines

Change Blindness: occurs because human beings are able to pay attention to only part of the visual sensations that they are exposed to on a momentby-moment basis. These are the parts that are remembered. Sensation Transduction: The conversion from sensory stimulus energy to action potential Sensory Adaptation: stop perceiving stimuli that remain relatively constant over prolonged periods of time. (like the constant ticking of a clock or dripping of a faucet) • Absolute threshold: Least energy for correct stimulus detection 50% of time (how sensitive you are to certain stimuli) • Measured in controlled conditions • stimulus reaches a physiological threshold (absolute threshold) when it is strong enough to excite sensory receptors and send nerve impulses to the brain Ex: Sight: candle flame at 30 miles on a clear, dark night Hearing: tick of a watch 20 feet away in a quiet room Smell: drop of perfume diffused throughout a three-room apartmen Taste: 1 teaspoon of sugar in 2 gallons of water Touch: bee’s wing falling on the cheek from 1 centimeter above • Just Noticeable Difference: smallest difference detectable 50% of the time Webster’s Law of Just Noticeable Difference states that Just Noticeable Difference between two stimuli is always a constant point at which a stimulus is detectable half the time it is present. Difference threshold changes depending on the intensity of the stimulus (ex: you notice a text in a quiet dark movie theatre but not a loud bright basketball game)

Subliminal Stimuli: (subliminal perception) stimuli just below level of conscious awareness/threshold (also known as subliminal messages) Visual Spectrum: the portion of the larger electromagnetic spectrum that we can see • The wavelengths that people can see are only a small part of the whole electromagnetic spectrum. • Humans can only see wavelengths ranging from 380 to 740 nm

ROYGBIV: Red Orange Yellow Green Blue Indigo Violet 1. The psychological properties of light include brightness, hue, and saturation Brightness: Corresponds to amplitude of light waves (dim light, bright light) • larger amplitudes appear brighter Hue: (color) the length of the light waves (reds, blues) • red is associated with longer wavelengths, greens are intermediate, and blues and violets are shorter in wavelength. Saturation: Highly saturated wavelengths are all the same, less saturated wavelengths vary; pink and red are the same hue (pink just whiter which less saturated) Blind Spot: area in the retina where the axons of the three layers of retinal cells exit the eye to form the optic nerve, insensitive to light. This accounts for when you can’t see an oncoming vehicle while in traffic when you look over there is in fact a blind spot and a vehicle parallel to your car becomes invisible

• Light enters the eye through the cornea and pupil • From the pupil, light passes through the lens to the retina, where it is transformed into nerve impulses • Nerve impulses travel to the brain along the optic nerve Iris: controls the size of the pupil, colored part of the eye (blue, green, brown) Cones: Located in the fovea, cones are sensitive to colors and work best in bright light. They are responsible for the sharpness of visual information and are found in the fovea. Rods: peripheral vision, rods detect changes in brightness but do not see color and function best in low levels of light. They do not respond to different colors and are found everywhere in the retina except the center, or fovea. • Responsible for night vision (black and white) Trichromatic Theory of Color Perception: Three types of cones—blue, green, and red, each responding maximally to different wavelengths of light • Firing rate of cones, and the combination of cones firing, determines color that is seen. Color Blindness: caused by defective cones in the retina of the eye and as a more general term, color-deficient vision is more accurate, as most people with ‘color blindness’ have two types of cones working and can see many colors. • Three Kinds of Color Blindness:

monochrome color blindness: people either have no cones or have cones that are not working at all. If they have cones, they only have one type and, therefore, everything looks the same to the brain—shades of gray. dichromatic vision: caused by the same kind of problem—having one cone that does not work properly Protanopia (red-green color deficiency): due to the lack of functioning red cones Deuteranopia: ) results from the lack of functioning green cones. In both, the individual confuses reds and greens, seeing the world primarily in blues, yellows, and shades of gray. called tritanopia (blue-yellow color deficiency): These individuals see the world primarily in reds, greens, and shades of gray

Dark adaptation is the recovery of the eye’s sensitivity to visual stimuli in darkness after exposure to bright lights. Light adaptation is the recovery of the eye’s sensitivity to visual stimuli in light after exposure to darkness. Afterimages: visual sensations that persist after the initial stimulus has been removed • when you burn your retinas by staring at the sun and see those orange spots when you look away, this is the AFTERIMAGE. It can also be seen when you stare at a black spot on your computer for a long time, when you look away all the colors you see are briefly inverted. This is called a negative afterimage Opponent-Process Theory: Four primary colors arranged in pairs, with each member of the pair as opponents; when one color of the pair is stimulated, the other is inhibited the stimulated cell (e.g., ganglion cell) cannot signal both colors at the same time. • Examples of pairs are black/white, yellow/blue, and green/red

• a cell that was excited by wavelengths associated with green would be inhibited by wavelengths associated with red, and vice versa

3 Aspects of Sound: • Pitch (Frequency) — the number of waves that pass a given point in a given time period and is often expressed in terms of hertz (Hz), or cycles per second. Longer wavelengths will have lower frequencies, and shorter wavelengths will have higher frequencies High-frequency sound waves are perceived as high-pitched sounds, while low-frequency sound waves are perceived as low-pitched sounds • Loudness (volume)— Higher amplitudes are associated with louder sounds Loudness is measured in terms of decibels (dB), a logarithmic unit of sound intensity. • Timbre (Purity)—Richness in the tone of sound, demonstrated by the way different musical instruments can play the same musical note at the same level of loudness, yet they still sound different (flute vs. trombone) Wavelength: wave cycles per second, or the length of a wave from one peak to the next. Amplitude: (decibels) the height of a wave as measured from the highest point on the wave (peak or crest) to the lowest point on the wave (trough).

5 basic tastes: 1. Salty

2. Umami 3. Sour 4. Sweet 5. Bitter Most of our experience of taste is related to smell. A raw potato and apple taste remarkably similar if you hold you nose when you taste them. Somesthetic Senses: The somatosensory system is a part of the sensory nervous system. The somatosensory system is a complex system of sensory neurons and neural pathways that responds to changes at the surface or inside the body. • Somatosensation is another word for sense of touch • Sense of touch originates in several different places in and on the body Skin Senses: touch, pressure, temperature, pain Kinesthetic Sense: location of body parts in relation to one another Vestibular Senses: movement, body position Kinesthetic Sense: allow the brain to know the position and movement of the body through the activity of special receptors responsive to movement of the joints and limbs. Vestibular Sense: contributes to the body’s sense of spatial orientation and movement through the activity of the otolith organs (up-and-down movement) and the semicircular canals (movement through arcs). • Kinesthetic and Vestibular senses sense the location of body parts in relation to the ground and each other • They control your sense of movement, balance, and body position • Motion sickness is explained by sensory conflict theory, in which information from the eyes conflicts with information from the vestibular sense, causing nausea. 3 Types of Perceptual Constancy:

• Size Constancy: the tendency to perceive objects as always being the same size, no matter how close or far away they are. • Shape Constancy: the tendency to perceive objects as remaining the same shape even when the shape of the object changes on the retina of the eye. • Brightness Constancy: the tendency to perceive objects as a certain level of brightness, even when the light changes Depth Perception: The ability to perceive the world in three dimensions Monocular Depth Perception: Depth cues that can be perceived by one eye alone, pictoral depth. Includes: • Interposition: the assumption that an object that appears to be blocking part of another object is in front of the second object and closer to the viewer, (overlap) • Linear perspective: tendency for parallel lines to appear to converge on each other (like a long road) • Relative size: perception that occurs when objects that a person expects to be of a certain size appear to be small and are, therefore, assumed to be much farther away. • Texture gradient: the tendency for textured surfaces to appear to become smaller and finer as distance from the viewer increases. • Aerial Perspective: perspective is the haziness that surrounds objects that are farther away from the viewer, causing the distance to be perceived as greater. • Motion Parallax: the perception of motion of objects in which close objects appear to move more quickly than objects that are farther away. Binocular depth cues: Cues for perceiving depth based on both eyes • binocular disparity, the slightly different view of the world that each of our eyes receives (close one eye, you see a different perspective than when you close the other eye)

Convergence: depth cue that involves the muscles of the eyes. When objects are far away, the eye muscles are more relaxed; when objects are close, the eye muscles move together, or converge. Illusions: perceptions that do not correspond to reality or are distortions of visual stimuli • Sometimes people perceive an object as moving when it is actually still: Stroboscopic Motion: seen in motion pictures, in which a rapid series of still pictures will appear to be in motion. Autokinetic effect: a small, stationary light in a darkened room will appear to move or drift because there are no surrounding cues to indicate that the light is not moving. Phi phenomenon: lights turned on in a sequence appear to move.

Gestalt Psychology: The word gestalt literally means form or pattern, but its use reflects the idea that the whole is different from the sum of its parts. a. brain creates a perception that is more than simply the sum of available sensory inputs b. figure-ground relationship: we tend to segment our visual world into figure and ground. Figure is the object or person that is the focus of the visual field, while the ground is the background. c. Proximity: things that are close to one another tend to be grouped together

• We group the letters of a given word together because there are no spaces between the letters, and we perceive words because there are spaces between each word • Similarity: things that are alike tend to be grouped together, like how we perceive football players wearing the same color jersey as being grouped together in a team...