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Objectives Chapter 1, Part 1

Objectives Chapter 1, Part 1. Illustrate and describe the perceptual cycle Explain the difference between top-down and bottom-up processing Compare and contrast psychophysical and physiological approaches to studying perceptual processes. Why Study Perception?.

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Objectives Chapter 1, Part 1

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  1. Objectives Chapter 1, Part 1 • Illustrate and describe the perceptual cycle • Explain the difference between top-down and bottom-up processing • Compare and contrast psychophysical and physiological approaches to studying perceptual processes

  2. Why Study Perception? • Understanding how you perceive the world • Language processing • Color vision • Depth perception • Future careers in Research • Multitasking - Driving and cell Phones • Optimizing Computer Monitor Displays • Medical applications • Assisting people with vision and hearing losses by understanding their needs

  3. Shall we play a game?

  4. Perception is cyclical. It never ends!

  5. The Perceptual Process - continued • Transduction • Change from environmental energy to electrical energy in the nervous system • Neural processing • Interconnected neurons that propagate the electrical signal from receptor cells throughout the brain

  6. Two Interacting Aspects of Perception • Bottom-up processing • Processing based on incoming stimuli from the environment • Also called data-based processing • Top-down processing • Processing based on the perceiver’s previous knowledge • Also called knowledge-based processing

  7. Approaches to the Study of Perception • Levels of Analysis • Observing perceptual processes at different scales • Psychophysical level - the stimulus-perception relationship (Line A) • Physiological level - the stimulus-physiology relationship (Line B) • These levels are interconnected, but we usually have to focus on specific parts in controlled experiments

  8. Objectives Chapter 1, Part 2 • Define psychophysics. • Describe ways to measure perception. • Explain mental processes with mathematical laws. • Compare and contrast Absolute Threshold and Difference Threshold.

  9. Psychophysics - Qualitative Methods • Description • Basic description of what a person perceives • First step in studying perception • Called phenomenological method • Recognition • Categorization of stimuli

  10. Psychophysics - Quantitative Methods • Absolute threshold - smallest amount of energy needed to detect a stimulus • Method of limits • Stimuli of different intensities presented in ascending and descending order • Observer responds to whether she perceived the stimulus • Cross-over point is the threshold

  11. Quantitative Methods - continued • Absolute threshold (cont.) • Method of adjustment • Stimulus intensity is adjusted continuously until observer detects it • Repeated trials averaged for threshold

  12. Quantitative Methods - continued • Absolute threshold (cont.) • Method of constant stimuli • 5 to 9 stimuli of different intensities are presented in random order • Multiple trials are presented • Threshold is the intensity that results in detection in 50% of trials

  13. Method of Constant Stimuli

  14. Quantitative Methods - continued • Difference Threshold (DL) - smallest difference between two stimuli a person can detect • Same methods can be used as for absolute threshold • As magnitude of stimulus increases, so does DL • Weber’s Law explains this relationship • DL / S = K

  15. Table 1.3 Weber fractions for a number of different sensory dimensions

  16. Quantitative Methods - continued • Magnitude estimation • Stimuli are above threshold • Observer is given a standard stimulus and a value for its intensity • Observer compares the standard stimulus to test stimuli by assigning numbers relative to the standard

  17. Quantitative Methods - continued • Magnitude estimation (cont.) • Response compression • As intensity increases, the perceived magnitude increases more slowly than the intensity • Response expansion • As intensity increases, the perceived magnitude increases more quickly than the intensity

  18. What it “seems’ like to you. Actual Intensity of the stimulus.

  19. Quantitative Methods - continued • Magnitude estimation (cont.) • Relationship between intensity and perceived magnitude is a power function • Steven’s Power Law • P = KSn

  20. Other Measurement Methods • Searching for stimuli • Visual search - observers look for one stimulus in a set of many stimuli and compares it to stored data (memory) • Reaction time (RT) - time from presentation of stimulus to observer’s response is measured

  21. Objectives Chapter 1, Part 2 • Define psychophysics. • Describe ways to measure perception. • Explain mental processes with mathematical laws. • Weber’s law • Steven’s Power Law • Compare and contrast Absolute Threshold and Difference Threshold. • Reading2 and 3 (synesthesia: Hard-Wired or Learned?) • What impact would synesthesia have on visual search?

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