Percepția și designul de experimente



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tarix29.08.2018
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Percepția și designul de experimente

  • Percepția și designul de experimente

  • Fundamente ale Psihofizicii










































Fracțiile Weber sunt adimensionale

  • Fracțiile Weber sunt adimensionale

  • Este posibil să se compare diferite modalități senzoriale

  • Exemplu: luminozitate si intensitatea acustică











Sensory Threshold

  • Sensory Threshold

    • Herbart (1824) critical boundary, above which neural activity signals the presence of a sensory event –ABSOLUTE


Threshold is a statistical concept, affected by:

  • Threshold is a statistical concept, affected by:

    • Chance variation in the nervous system
    • Random signal noise
    • Intensity of signal
    • Observer’s criterion






One way of measuring tactile sensitivity is to determine the smallest amplitude of vibration of the skin that can be detected by an observer

  • One way of measuring tactile sensitivity is to determine the smallest amplitude of vibration of the skin that can be detected by an observer

  • Verrilo’s experiment (1963): a stimulator attached to a vibrator was placed in contact with the base of the thumb

  • The size of the stimulator was varied over a range of 0.005 cm2 to 5.1 cm2



When the stimulator was larger then 0.02 cm2, vibrotactile sensitivity was greatest in the frequency region around 250 Hz



From these findings Verrillo concluded that the skin contains at least two receptors systems.

  • From these findings Verrillo concluded that the skin contains at least two receptors systems.

    • One system summates energy over space and accounts for the U-shaped frequency function obtained when all but the smallest stimulators are used (Pacinian corpuscle)
    • The other system accounts for the flat frequency (no spatial summation) for very small contactors


In further experiments stimuli with a much wider frequency range were presented

  • In further experiments stimuli with a much wider frequency range were presented

  • The results provided the basis for a four channel model of mechanoreceptors (1988)

    • P channel (Pacinian) high frequency
    • NPI (Meissner) 2-40 Hz
    • NPIII (Merkel) 0.4-2 Hz
    • NPII (Ruffini) only if Pacinian are deficient


P channel (Pacinian) H.F.

    • P channel (Pacinian) H.F.
    • NPI (Meissner) 2-40 Hz
    • NPIII (Merkel) 0.4-2 Hz
    • NPII (Ruffini)



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