HCR - Definition of 'Psychophysics'

Psychophysics investigates the relationship between sensation ($\Psi$) in the psychological domain and stimuli ($\Phi$) in the physical domain.

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• Studying perception
  • Psychophysics refers to the methodology of studying perception (designing experiments, formulating models).

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• Sensation
  • For centuries thinkers have recognized the importance of understanding sensation in order to answer many questions like for examples:
    1. Is the perception an active or passive process?
    2. Is perception veridical? (is it truthful)
    3. Can perceptual mechanism be modified?
    4. Can we integrate different signals from different sensory modalities?
    5. Can sensory modalities interact?

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• Principal Problem
  • The goal of perception is to acquire accurate and reliable information about the environment.
  • How to establish the relation between perceptions and the underlying brain mechanism?

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• Objective
  • We need psychophysics because:
    Physical dimensions $\ne$ Perceptual dimensions:
    
  • Perception is context dependent:
    
    
  • Psychophysics helps in understanding how to establish the relation between perceptions and the underlying brain mechanisms.

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• Sensory threshold
  • The central concept of psychophysics is that of sensory threshold
  • Mental events had to be stronger than some critical amount in order to be consciously experienced

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• Measurement of the sensitivity limits
  • Weber and Fechner were interested in the measurement of the sensitivity limits of the human sense organs.
  • Using measurement techniques of physics and well trained human observers, were able to specify the weakest detectable sensation in terms of stimulus energy necessary to produce them.