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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)?

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Psychophysics

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  1. 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?

  2. 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

  3. Discrimination • Difference thresholds (jnd’s) • Weber’s Law (DI = kI) • Reaction time (RT) measures • Simple RT • Choice RT

  4. 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

  5. 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

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