Percepția și designul de experimente

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Percepția și designul de experimente










































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:







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

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

  • Increasing the size of the stimulator, the threshold proportionally decreases

  • For 0.02 cm2 stimulators or smaller, no spatial summation was observed



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) H.F.

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



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