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For more information, please see full course syllabus of AP Psychology
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Thresholds & Signal Detection Theory

  • Psychophysics is the study of relationships between the physical characteristics of stimuli, such as their intensity, and our psychological experience of them
  • Ernst Weber was a founder of early experimental psychology and studied absolute thresholds
  • Gustav Fechner founded psychophysics and showed the relationship between a psychological sensation and physical intensity of a stimulus
  • Sensory transduction is the conversion of one form of energy into another such as transforming wave energies of sight and sound into electrical signals the brain can interpret
  • Weber’s Law is the amount of change needed to produce a constant just-noticeable difference
  • Signal Detection theory predicts how and when we detect the presence of a faint stimulus (signal) amid background stimulation (noise). Assumes there is no absolute threshold and that detection depends partly on a person’s experience, expectations, motivation, and alertness
  • Sensory adaptation is when neural or sensory receptors reduce their sensitivity to a continuous, unchanging stimuli
  • Top-down processing is information processing guided by higher-level mental processes, as when we construct perceptions drawing on our experience and expectations
  • Bottom-Up Processing is analysis that begins with the sensory receptors and works up to the brain’s integration of sensory information
  • Hubel and Wiesel showed how there are neurons in the brain the deal with specific aspects of a stimulus and not the entire set of information entering the visual system
  • Perceptual set is a mental disposition to perceive one thing and not another
  • Subliminal perception is not what most people think of and is not a reliable way to change behavior

Thresholds & Signal Detection Theory

Lecture Slides are screen-captured images of important points in the lecture. Students can download and print out these lecture slide images to do practice problems as well as take notes while watching the lecture.

  1. Intro
    • Sensation and Perception (6-8%)
    • General Properties of Sensory Systems
    • Sensation and Perception
    • Terms
    • Psychophysics
    • Ernst Weber
    • Gustav Fechner
    • Sensory Transduction
    • Absolute Threshold
    • Difference Threshold
    • Weber's Law
    • Signal Detection
    • Sensory Adaptation
    • Top-Down Processing
    • Bottom-Up Processing (AKA Feature Analysis)
    • Sensation Chart Overview
    • David Hubel and Torsten Wiesel
    • Perceptual Set
    • Perceptual Set
    • Perceptual Set -- Culture and Context Effects
    • Perceptual Set -- Culture and Context Effects
    • Basic Illusions -- Muller-Lyer
    • Basic Illusions -- Poggendorf
    • Basic Illusions -- Ponzo
    • Basic Illusions -- Hermann Grid
    • Attention
    • Perceptual Defense and Subliminal Perception
    • Review