Psychophysics
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Psychophysics. Introduction Study of relationship between physical stimuli and sensations Gustav Fechner Three psychophysical problems What is the weakest stimulus that can be detected (the stimulus threshold)?

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Psychophysics
Psychophysics

  • Introduction

    • Study of relationship between physical stimuli and sensations

    • Gustav Fechner

    • Three psychophysical problems

      • What is the weakest stimulus that can be detected (the stimulus threshold)?

      • What is the smallest difference between stimuli that can be detected (the difference threshold)?

      • What is the relationship between intensity of stimulus and intensity of sensation?


Detection
Detection

  • Classical psychophysical methods

    • Method of constant stimuli

    • Method of limits

    • Adaptive testing -- staircase method

  • The theory of signal detection

    • Signal detection methodology

    • Outcome matrices

    • Sensitivity and criterion measurement


Discrimination
Discrimination

  • Difference thresholds (jnd’s)

  • Weber’s Law (DI = kI)

  • Reaction time (RT) measures

    • Simple RT

    • Choice RT


Identification
Identification

  • Information theory

    • Information = reduction of uncertainty

    • Quantification of information: the bit

    • Channel capacity

    • Hick’s Law: Choice RT is a linear function of amount of information in the stimulus


Scaling
Scaling

  • Quantification of the strength of a sensation

  • Prothetic vs metathetic continua

  • Indirect scaling: Fechner’s Law

    • S = k log(I/Io)

  • Direct scaling: Magnitude estimation and Stevens’ Law

    • (S = aIm)

  • Cross-modality matching

  • Multidimensional scaling

  • Context and bias: Adaptation Level theory