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Signal detection

Signal detection. Psychophysics. Psychophysics The study of the relationship between physical stimulation and subjective sensations. Signal-Detection Theory The theory that detecting a stimulus is jointly determined by the signal and the subject’s response criterion. Psychophysics .

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Signal detection

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  1. Signal detection Psychophysics

  2. Psychophysics • The study of the relationship between physical stimulation and subjective sensations. • Signal-Detection Theory • The theory that detecting a stimulus is jointly determined by the signal and the subject’s response criterion.

  3. Psychophysics • The formal study of the relationship between the properties of stimuli as measured by a physical scale and the psychological impressions of those stimuli. • Lawful relationships were uncovered between stimulus differences, measured on a physical scale, and experienced differences. • Measurable stimulus values were observed below and above the threshold of awareness

  4. Psychophysics Relationship between physical stimuli and percepts Objective measurement of stimuli Eg varying light intensity, frequency of tones What can you hear see taste smell etc???

  5. Psychophysics • Method of limits – descending and ascending • Method of constant stimuli – random level • Method of adjustment - control • 2AFC (2 alternative choice or 3..) • Go–no go • 2IFC (2 interval choice or 3..) demos

  6. The Method of Limits A psychophysical method where a standard stimulus is compared with various values of comparison stimuli presented in both ascending and descending series. The task of the subject is to specify when the standard and the variable appear to be the same.

  7. The Method of Constant Stimuli A psychophysical method where a standard stimulus is judged against comparison stimuli. Various values of the comparison stimuli above and below the standard stimulus are presented on a random basis. The task of the subject is to specify whether the comparison is =, <, > standard.

  8. Absolute Threshold • The smallest amount of stimulation that can be detected • Just Noticeable Difference • The smallest amount of change in a stimulus that can be detected

  9. Regardless of the sensory domain, there are three main topics in the psychophysical classification scheme: absolute thresholds discrimination thresholds scaling • Typically small n experiments

  10. Signal Detection Theory • Find the signal in the noise

  11. Gives all possible choices and we can determine the sensitivity and response bias

  12. Criterion of decision

  13. d’ or how much separation?d' = separation / spread d' = ZFA - ZHit

  14. Signal detection applet

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