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Chapter 4

Chapter 4 Notes

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Department
Psychology
Course
PSY 102
Professor
Benjamin Dyson
Semester
Fall

Description
Illusion: the way you perceive the stimulus doesn’t match its physical reality Sensation: detection of physical energy by sense organs (eyes, ears, skin, nose, & tongue), which then send information to the brain Perception: the brains interpretation of raw sensory inputs - Sensation first allows us to pick up the signals in our environments, & perception than allows us to assemble these signals into something meaningful Two Sides of the Coin: Sensation & Perception - Our brain picks & chooses among the types of sensory information it uses, often relying on expectation & prior experiences to fill the gaps & simplify processing Transduction: process by which the nervous system converts an external stimulus, like light or sound into electrical signals within neutrons Sense receptor: specialized cell responsible for converting external stimuli into neutral activity for a specific sensory system Sensory adaptation: activation is greatest when a stimulus is first detected. Ex. Sitting on a chair Psychophysics: study of how we perceive sensory stimuli based on their physical characteristics. (Gustav Fechner) Absolute threshold: the lowest intensity at which a stimulus can be detected correctly 50% of the time - The lower the absolute threshold, the greater the sensitivity Just noticeable difference(JND): smallest change in the intensity of a stimulus that we can detect. Ex. song sound Weber’s law: there is a constant proportional relationship between the JND & the original stimulus intensity Signal detection theory: theory of how stimuli are detected under different condition. Ex. trying to figure out what someone is saying on a cell phone when there’s a lot of static in the connection Signal-to-noise ratio: it becomes harder to detect a signal as background noises increases Response biases: frequency of false negatives & false positives helps us measure how biased subjects are to respond “yes” or “no” in general. Ex. people lying or telling the truth when a sound is or isn’t played Sensory Systems Johannes Müller: specific nerve energies – even though there are many distinct stimulus energies (light, sound, touch) the sensation we experience is determined by the nature of the sense receptor, not the stimulus Phosphenes: vivid sensations of light cause by pressure on your eyes receptor cells. Ex. Rubbing eyes waking up McGurk effect: we integrate visual & auditory information when processing spoken language, & our brains automatically calculate the most probable sound given the information from the 2 sources Rubber hand illusion: shows how our senses of touch & sight interact to create a false perceptual experience. Ex. rubber hand on table, experimenter brushes hand with a paintbrush – person feels it even thought it’s not theirs Synesthesia: condition when people experience cross-model sensation. Ex. hearing sounds when looking at colours (coloured hearing), or even tasting colours. Sir Francis Galton was the first to describe this Grapheme-colour synesthesia: 6 may seem red & a 5 may seem green Lexical-taste synesthesia: words have associated tastes, letters take on “personality traits” – ‘A’ = bold Perception: When Our Senses Meet Our Brains Parallel processing: being able to process all 5 senses into one perception Bottom-up processing: process where a whole is constructed from parts. Starts with the raw stimuli we perceive & ends with our synthesizing them into a meaningful concept Top-down processing: Seeing the most obvious thing first. Ex. Seeing the saxophone player first vs. the women Perceptual set: when our expectations influence our perceptions. Ex. Seeing the young women vs. the old one Perceptual constancy: process by which we perceive stimuli consistently across varied conditions. Door Ex.: Shape constancy: we still see the door as a door even when it appears as a rectangle or a trapezoid Size constancy: ability to perceive objects as the same size no matter how far away they are from us Colour constancy: ability to perceive colour consistently across different levels of lighting.Ex.Checkerboard Selective attention: process of selecting one sensory channel & ignoring or minimizing others. Ex. Like a TV Filter theory of attention: view attention as a bottleneck through which information passes. (Donald Broadbent) - Experiment: dichotic listening: subjects hear 2 different messages, 1 in the left ear, the other in the right. Subjects were told to ignore a message in a given ear, then asked to repeat the message – shadowing (Anne Treisman). Subjects would repeat the message but would mix part of the other message they weren’t supposed to hear, just because it made sense to add it - Shadowing: we cannot attend completely to more than one thing at a time Cocktail party effect: ability to pick out an important message, like your name, in a convo that doesn’t involve you Inattentional blindness: failure to detect stimuli in plain sight when our attention is focused elsewhere. Ex.Gorilla Change blindness: failure to detect obvious change in one’s environment. Ex. Pilot landing example Binding problem: great mysteries of psychology. We don’t know how our brains manage to combine or “bind” these diverse pieces of information into a unified whole. Ex. characteristics of an apple (red, round, smooth, etc.) Subliminal information processing: we process many of the sensory inputs to which we’re exposed unconsciously, & that many of our action occur with little or no forethought or deliberation Subliminal Perception: processing of sensory information that occurs below the limen (level of conscious awareness) Ex. uncontrollable desire to eat a cheeseburger – TV example Subliminal Persuasion: subthreshold influences over our votes in elections, product choices, & life decisions - Subliminally present words related to thirst – drink slightly influences how much people drink, cola doesn’t influence beverage choice. Ex. Subliminal self-help audiotapes – repeated messages: “Feel better about yourself” Reversed subliminal messages influence behaviour. “Backmasking” claims of music having backwards messaging Seeing: The Visual System Life: The Energy of Life - Form of electromagnetic energy – energy composed of fluctuating electric & magnetic waves - Visible lights has a wavelength in the hundreds of nanometers (one billionth of a metre) (Rainbow strip) Experience of colour depends on 3 dimensions: Brightness: influenced directly by the intensity (or amount) of reflected light that reaches our eyes Hue: when we describe the colour of an object Saturation: perceived purity of a colour. Highly saturated = vivid (red like a fire engine). Low = washed out The Eye Sclera: the white of the eye Iris: coloured area of the eye (blue, brown, green, or hazel) – contains muscles that control the pupil - Chemicals responsible for the eye are called pigments – only 2 – melanin (brown) & lipochrome (yellowish-brown) – account for all of the remarkable variations in eye colours Pupil: Opening in the centre of the it is that lets in light Pupillary reflex: walking out of a building into bring sunshine – our eyes decrease the amount of light allowed into them. Ex. Shining a flashlight into one eye Belladonna: juice from a plant that European women have added to their eyes to dilate their pupils Cornea: curved, transparent dome that bends incoming light to focus the incoming visual image at the back of the eye Lens: elastic structure behind the pupil that becomes thinner to focus on distant objects and thicker to focus on nearby objects. The ability to see clearly depends on the lens’s ability to focus the image directly onto the retina Accommodation: lenses change shape to focus light on the back of the eyes; adapt to different perceived distances of objects ^ ^ Myopia: (nearsightedness) if you have good vision for nearby objects but has difficulty seeing far away objects then you probably suffer from myopia - In near-sighted people, the lens focuses the visual image in front of the retina, resulting in blurred image for faraway objects - This condition generally occurs because the eyeball is longer (front to back) than normal Hyperopia: (farsightedness) is when some people have excellent distance vision but have difficulty seeing close- up objects clearly - Occurs when the lens does not thicken enough and the image is therefore focused on a point behind the retina (too far from the lens). The aging process shortens the eyeball and sometimes causes hyperopia Presbyopia: loss of flexibility in the lens due to aging Retina: innermost layer of the eye (at the back of the eye), receives inverted image from the lens but the brain reconstructs the visual input into the image that we perceive Fovea: central part of the retina where light rays are most sharply focused on. It is responsible for acuity – sharpness of vision Rods: receptor cells in the retina allowing us to see in low levels of light Dark adaptation: entering a dimly lit move theatre from a bright environment. Take about 30 mins or about the time it takes rods to regain their maximum sensitivity to light Cones: receptor cells in the retina allowing us to see in colour (shaped as small cones) Photopigments: chemicals that change following exposure to light - Photopigments in roads is rhodopsin – Vitamin A (in abundance in carrots) is need to make this Ganglion cells: cells in the retinal circuit that contain axons; bundle them all together, & depart the eye to reach the brain Optic nerve: transmits impulses from the retina to the rest of the brain (contains the axons of ganglion cells) Optic chiasm: after the optic nerves leave both eyes, they come to a fork in the road; half of the axons cross in the optic chiasm & the other half stay on the same side Blind spot: place where the optic nerve connects to the retina (contains no rods & completely devoid of sense receptors) Eye muscle: One of the 6 surrounding muscles that rotate the eye in all directions Visual Perception - Hubel & Wiesel studied activity in the visual cortex of cats viewing slits of light on a screen Visual responses were specific to: a) Slits of dark on light – minuses on pluses b) Light on dark – pluses on minuses c) Particular orientation, such as horizontal, oblique, or vertical Feature detection: ability to use certain minimal patterns to identify objects Feature detector cell: cells that detects lines (of specific lengths, complex shapes, & moving objects) & edges (perceive many human-made objects – furniture, laptops, & corners of a page) - Along 2 major routes, 1 of which travels to the upper parts of the parietal love, & the other of which travels to the lower part of the temporal lobe Subjective contours: when our brain provides missing information about outlines Gestalt (whole) principles: rules of governing how we perceive objects as whole within their overall context - These principle provide a road map for how we make sense of our perceptual words Main Gestalt principles formulated by psychologists Max Wertheimer, Wolfgang Kohler, & Kurt Koffka(early 20c): 1. Proximity: objects physically close to each other tend to be perceived as unified wholes (all red dots) 2. Similarity: objects perceived as similar, will be perceived as belonging together(red & yellow dot rows) 3. Continuity: still perceive objects as whole, even if other objects block part of them (cross not 4 little lines) 4. Closure: when partial visual information is present, our brains fill in what’s missing (dotted circle) 5. Symmetry: perceiving objects that are symmetrically arranged as wholes more often than those that aren’t 6. Figure-ground: making a decision to focus attention on what we believe to be the central figure, & largely ignore what we believe to the background (trophy or side view of 2 people?) Bistable: being able to perceive an image in 2 ways - Motion perception is a fundamental aspect of vision & is present in all visual organisms Phi phenomenon: (Max Wertheimer) illusionary perception of movement produced by the successive flashing of images. Ex. perceptions of what’s moving & what’s not based on the only partial information, with our brains taking their best guesses about what’s missing Trichromatic theory: idea that colour vision is based on our sensitivity to 3 primary colours – blue, green, & red Colour blindness: inability to see some or all colours. Often b/c of the absence or reduced number of 1 or more types of cones stemming from genetic abnormalities Monochromats: someone who has only 1 type of cone & thus lose all colour vision (extremely rare, 0.0007% pop.) Dichromats: someone who has 2 types of cones & missing only 1 type. - Red-green dichromats se considerable colour but can’t tell between reds Trichromates: we & our close primate relatives (apes & some monkeys + humans) process 3 kinds of cones - Most mammals includin
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