Sensation and perception ch 3 bb


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  • Weber's Law states that the ratio of the increment threshold to the background intensity is a constant. So when you are in a noisy environment you must shout to be heard while a whisper works in a quiet room. And when you measure increment thresholds on various intensity backgrounds, the thresholds increase in proportion to the background.
  • Signal detection theory (SDT) is used when psychologists want to measure the way we make decisions under conditions of uncertainty, such as how we would perceive distances in foggy conditions. SDT assumes that the decision maker is not a passive receiver of information, but an active decision-maker who makes difficult perceptual judgments under conditions of uncertainty. In foggy circumstances, we are forced to decide how far away from us an object is based solely upon visual stimulus which is impaired by the fog. Since the brightness of the object, such as a traffic light, is used by the brain to discriminate the distance of an object, and the fog reduces the brightness of objects, we perceive the object to be much further away than it actually is
  • Our experience and expectations enable us to immediately perceive the scrambled letters as meaningful words and sentences.
  • 3. Perceptual Constancy a. Shape and size constancies b. Size Distance relationship c. Lightness constancy
  • Sensory thresholds and adaptation are not the only phenomena that influence what we sense and perceive. Another is our capacity to attend to stimuli.
  • Circles in the front or circles in the back. Can only see one image at a time due to selective attention.
  • Change blindness: so focused on one thing, fail to see something else. Example: gorilla walking through basketball competition Change blindness--the failure to detect (often large) changes to visual scenes, Change deafness: so focused, don’t notice the change in sound. Failure to detect auditory changes. Example: memorizing list and don’t notice change in speaker.
  • Sensation and perception ch 3 bb

    1. 1. Chapter 3-1
    2. 2. <ul><li>The process that occurs when special receptors in the sense organs are activated, allowing various forms of outside stimuli to become neural signals in the brain. </li></ul>
    3. 3. <ul><li>The method by which the sensations experienced at any given moment are interpreted and organized in some meaningful fashion. </li></ul><ul><li>Sensation provides the raw information that perception constructs into experiences. </li></ul>
    4. 4. <ul><li>Sensation occurs when special receptors in the sense organs are activated, allowing various forms of outside stimuli to become neural signals in the brain. </li></ul><ul><li>Sensory Transduction: the process of converting outside stimuli such as light, into neural activity. </li></ul><ul><ul><li>Light into sight </li></ul></ul><ul><ul><li>Vibrations into sound </li></ul></ul><ul><ul><li>Pressure/temperature into touch/feeling </li></ul></ul><ul><ul><li>Chemicals into taste and smell </li></ul></ul>
    5. 5. <ul><li>The minimum amount of stimulation a person needs for a particular stimulus to be detected 50% of the time. </li></ul><ul><li>Or….the minimal amount of energy necessary to stimulate the sensory receptors </li></ul><ul><li>Just barely noticeable. </li></ul><ul><li>Individual to the person. </li></ul><ul><li>May vary due to circumstances. </li></ul>
    6. 6. <ul><li>When can you actually hear your alarm clock ticking? </li></ul><ul><li>How loud does your cell phone need to be in order to hear it? </li></ul><ul><li>How much salt do you add to your hamburger before you can taste it? </li></ul><ul><li>How damp does something have to be before you say it’s damp? </li></ul><ul><li>How much perfume does someone need to wear before you can smell it? </li></ul>
    7. 7. <ul><li>The minimum difference between two stimuli required for detection 50 percent of the time. </li></ul><ul><li>We experience the difference threshold as a just noticeable difference (jnd) . </li></ul>
    8. 9. <ul><li>the principle that, to be perceived as different, two stimuli must differ by a constant minimum percentage (rather than a constant amount). </li></ul><ul><ul><li>Weighing fruit </li></ul></ul><ul><ul><li>Speaking loud enough to be heard in a crowd </li></ul></ul><ul><ul><li>Changing intensity of the lights to be noticed </li></ul></ul><ul><ul><li>How many jelly beans are eaten from the jar before you actually notice? </li></ul></ul><ul><ul><li>Sales principle! </li></ul></ul>
    9. 10. <ul><li>Diminished sensitivity as a consequence of constant stimulation. </li></ul><ul><li>Consider that you quickly filter out: </li></ul><ul><ul><li>The sensation of clothing on your skin. </li></ul></ul><ul><ul><li>The color of the room. </li></ul></ul><ul><ul><li>A foul smell in your house. </li></ul></ul><ul><ul><li>Noise that is constant. </li></ul></ul><ul><li>Exception to the rule: Eyesight! The eye constantly quivers in order to prevent sensory adaption. </li></ul>
    10. 11. <ul><li>A theory prediction how and when we detect the presence of a faint stimulus (signal) amid background stimulation (noise). </li></ul><ul><li>Assumes there is no single absolute threshold and that detection depends partly on a person’s experience, expectations, motivation, and level of fatigue. </li></ul>
    11. 12. <ul><li>We are designed to detect important features in our environment, for efficiency and survival. </li></ul><ul><li>Psychological factors can influence how we detect signals, for example: </li></ul><ul><ul><li>Mom wakes up immediately with baby sounds. </li></ul></ul><ul><ul><li>Name being spoken in crowded room. </li></ul></ul><ul><li>Repeated exposure to signals over time can diminish our sensitivity. (airport scanners?) </li></ul><ul><li>SDT relates to decision-making. </li></ul>
    12. 13. <ul><li>The method by which the sensations experienced at any given moment are interpreted and organized in some meaningful fashion. </li></ul><ul><li>Take into account: </li></ul><ul><ul><li>Experience </li></ul></ul><ul><ul><li>Expectation </li></ul></ul><ul><ul><li>Motivation </li></ul></ul>
    13. 14. <ul><li>analysis that begins with the sensory receptors and works up to the brain’s integration of sensory information. </li></ul>
    14. 15. <ul><li>information processing guided by higher-level mental processes, as when we construct perceptions drawing on our experience and expectation. </li></ul>
    15. 17. <ul><li>Aoccdrnig to rscheearch at Cmabrigde Uinervtisy, it deosn't mttaer in waht oredr the ltteers in a wrod are, the olny iprmoetnt tihng is taht the frist and lsat ltteer be at the rghit pclae. The rset can be a total mses and you can sitll raed it wouthit a porbelm. Tihs is bcuseae the huamn mnid deos not raed ervey lteter by istlef, but the wrod as a wlohe. </li></ul><ul><li>Perception guiding sensation. </li></ul>
    16. 18. <ul><li>Perceptual Set: the tendency to perceive things a certain way because previous experiences or expectations influence those perceptions. </li></ul><ul><li>What do you see here? </li></ul>
    17. 19. <ul><li>Bruner & Minturn, 1955 illustrated how expectation could influence set by showing participants an ambiguous figure '13' set in the context of letters or numbers e.g. </li></ul><ul><li>Depending on what you are </li></ul><ul><li>focusing on, you will see </li></ul><ul><li>something different. You </li></ul><ul><li>will expect something </li></ul><ul><li>different. </li></ul>
    18. 21. <ul><li>A study by Bugelski and Alampay, 1961 using the 'rat-man' ambiguous figure demonstrated the importance of expectation. </li></ul><ul><li>Participants were shown either a series of animal pictures or neutral pictures prior to exposure to the ambiguous picture. They found participants were significantly more likely to perceive the ambiguous picture as a rat if they had had prior exposure to animal pictures </li></ul>
    19. 22. <ul><li>Many of your memories may actually be formed around perceptual sets that were established at an earlier date. </li></ul><ul><li>For example: </li></ul><ul><li>Tell me about the last time you were at the airport. </li></ul><ul><li>What did your kitchen look like when you left the house today? </li></ul>
    20. 23. <ul><li>Perceiving objects as unchanging (having consistent lightness, color, shape, and size) even as illumination and retinal images change! </li></ul>
    21. 25. Point A Point B
    22. 26. <ul><li>Brightness (or lightness) is our ability to perceive an object as having a constant brightness even when its illumination—the light cast upon it changes. </li></ul><ul><li>Color constancy enables us to perceive the color of an object as unchanging even when its illumination changes. </li></ul>
    23. 27. <ul><li>Test your awareness video -- YouTube </li></ul>
    24. 28. <ul><li>The focusing of conscious awareness on a particular stimulus, as in the cocktail party effect. </li></ul><ul><li>At any moment our awareness focuses, like a flashlight beam, on only a limited aspect of all that we experience. </li></ul>
    25. 30. <ul><li>Failing to see visible objects when our attention is directed elsewhere. </li></ul><ul><ul><li>Missing traffic signals because talking on cell phone. </li></ul></ul><ul><ul><li>Train engineer missing warning signal due to text messaging! </li></ul></ul><ul><li>Change deafness </li></ul><ul><li>Change blindness – </li></ul><ul><ul><li>See change blindness video </li></ul></ul>