Ch. 4- Two sides of the coin- Sensation is the detection of physical energy by our sense organs, which send that informationto the braino The external stimulus is converted by a sense receptor (specialized cell) into neural activity via transduction—the process by which the nervous system converts an external stimulus, like light or sound, into electrical signals within neuronso Activation is highest when stimulus is first detected, then sensory adaptation occurs- Perception is the brain’s interpretation of raw sensory data- When the way we perceive a stimulus does not match reality, that’s an illusion- Psychophysics—study of how we perceive sensory stimuli based on their physical characteristicso Absolute threshold—is the lowest level of a stimulus we can detect 50% of the time A single candle 30 miles away 50 oderant moleculeso The just noticeable difference is the smallest amount of stimulus change we can detecto Weber’s law—the stronger the stimulus, the greater change needed to detect - Signal detection theory—theory regarding how stimuli are detected under different conditions- When our senses crosso Synesthesia—a rare condition in which people experience cross-modal sensations, like hearing sounds when they see colors—sometimes called “colored hearing”—or even tasting colors- When senses meet the braino After being transduced, our brains then organize the sensory data into meaningful conceptso Our brains piece together: What’s in our sensory field What was there a moment ago What we remember from our pasto The multitasking brain We attend to multiple senses at once, called parallel processing Bottom-up (take a stimulus’ parts and try to construct the parts together) vs. top-down processing (guessing the stimulus from the parts)- Perceptual Hypotheseso Perpetual sets occur when our expectations influence our perceptionso Perceptual constancy allows us to perceive stimuli consistency across conditions We don’t see the size, shape, or color of an object changing despite the objective fact that they do Color perception in particular derives from context- The Role of Attentiono Selective attention allows us to choose which sensory inputs to focus on and which to ignore/minimize The other “channels” are still being processed at some level, though- Cocktail party effecto We’re poor at detecting stimuli in plain sight if our attention is focused elsewhere- Binding Problemo One of the great mysteries of psychology is just how our brains combine all the various stimuli around us into a coherent wholeo The look, feel, smell, and taste of an apple all rely on different areas of the brain to process, but, we just see an apple!- Subliminal information processingo We process many sensory inputs unconsciously and many of our actions occurs with little to no forethought or deliberationo If we can detect stimuli without knowing it, does that change our behavior?- Subliminal perceptiono The processing of sensory information that occurs below the level of conscious awarenesso Can have a brief, short-term impact on behaviors and attitudeso Effect disappears when subjects are aware of or suspect subliminal influences- Subliminal Persuasion o Fairly unlikely to produce large-scale or enduring attitudes or decisional changeso Subliminal self-help tapes have been shown to be ineffective Illusory placebo effecto Reversed subliminal messages also ineffective- Extrasensory perception (ESP)o The perception of events outside the known channels of sensationo According to parapsychologists, there are three major types Precognition—predicting events before they occur Telepathy—reading other people’s minds Clairvoyance—detecting the presence of objects or people that are hidden fromview- Evidence for ESPo Early studies by JS Rhine using Zener cards reported positive resultso But, methodological problems plagued the study and no one else could replicate his results- Why people believeo Despite the lack of scientific evidence, over 40% of American adults believe in ESPo Illusory correlations and not understanding chance occurrences- The visual systemo The human visible spectrum is a narrow band of light that we respond too Other animals may have a more restricted or greater spectrumo We perceive brightness (intensity) and hue (color)o Mixing lights produces white (additive)—green, blue, redo Mixing pigments produces black (subtractive)—yellow, cyan, magenta- Structure of the eyeo Sclera—white portion of the eyeo Iris—colored portion and controls how much light enters the eyeo Pupil—hole where light enters the eyeo Cornea—transparent cells that focus light on the back of the eyeo Lens—bends light by changing its curvatureo Glasses change the way light enters the eye to help correct myopia or hyperopiao Retina—thin membrane at the back of the eye Fovea—center part of retina, responsible for acuityo Light hits two types of sense receptors on the retina—rods (light) and cones (color) Dark adaptationo Optic nerve exits the back of the eye and is composed of the axons of the ganglion cells Causes a blind spoto Most of the axons go to the thalamus and then the visual cortex, but some go to midbrain- Visual perceptiono Different cortical cells respond maximally to different types of stimulio Feature detector cells allow us to detect lines and edges- Gestalt principles (6)o Rules that govern how we perceive objects as wholes within their overall contexto Proximity—objects physically close to each other tend to be perceived as unified wholeso Similarity—all things being equal, we see similar objects as comprising a whole, much more so than dissimilar objectso Continuity—we still perceive objects as wholes, even if other objects block part of them.o Closure—when partial visual information is present, our brains fill in what’s missing.o Symmetry—we perceive objects that are symmetrically arranged as wholes more oftenthan those that aren’to Figure-ground—perceptually, we make an instantaneous decision to focus attention onwhat we believe to be the central figure, and largely ignore what we believe to be the background.- Visual Perceptiono To determine motion, the brain compares visual frames of what is to what was Phi phenomenon- Color perceptiono Different theories of color perception explain different aspects of our ability to detect