Sensation

• ​Definition

  • ​Psychological

    • ​fundamental,raw experiences
      

  • ​Biological

    • ​involves the sense organ,the neural pathway
      

• ​Threshold sensitivity
  

  • Absolute threshold
    

    • ​the minimun intensity
      

    • ​detection

  • ​Difference threshold
    

    • ​jnd

    • ​discrimination

  • ​suprathreshold sensation
    

• ​Signal detect theory
  

  ‒Theory of how people detect signals

  ‒The theory is based on the idea that signals are always embedded in noise, and thus the challenge is to distinguish signal from noise

  • ​Signal
    

    • ​important information
      

  • ​Noise

    • ​unimportant information
      

• ​Vision

  • ​stimuli is light
    

    • ​electromagnetic energy
      

  • ​Visual system
    

    • ​Form the image
      

      • ​the cornea
        

        The cornea is the transparent front surface of eye:Light enters here, and rays are bent inward by it to begin the formation of the image.

        
        

      • ​the lens
        

        The lens complete the process of focusing the light on the retina.To focus on objects at different distances, the lens changes shape.(accomodation)

        • ​not flat enough
          

          • ​myopic(near-sighted)

        • ​not spherical enough
          

          • ​hyperopic(farsighted)

      • ​the pupil
        

        The pupil change size in different level of light, thereby helping to ensure that enough light passes through the lens to maintain image quality at different light levels.

        • ​largest in dim light
          

        • ​smallest in bright light
          

    • Transduction system
      

      Absorption of light by photo pigments in receptors starts transduction process neural impulse travels to brain via neurons.

      
      

      • ​Rods

        • ​For seeing at night
          

        • ​cannot distinguish details
          

        • ​periphery

      • Cones

        • For seeing during the day
          

        • ​can distinguish details and work for color vision
          

        • ​fovea

  • ​Dark adaptation
    

    Process that leads to increased sensitivity to light after being in the dark.

    • ​The pupil changes size
      

    • ​Photochemical changes in the receptors
      

    • ​dark adaptation curve
      

  • ​Seeing color
    

    • ​Color

      • ​short wavelength
        

        • ​blue

      • ​medium wavelength
        

        • ​green

      • ​long wavelength
        

        • ​red

    • ​Color mixture
      

      • ​metamers

    • ​Color theory
      

      • ​Trichromatic theory
        

        • 3 types of receptors
          

          • ​short-wavelength cones
            

          • ​medium-wavelength cones
            

          • ​long-wavelength cones
            

        • ​receptor level
          

        • ​explains color deficiencies
          

          • ​Dichromats

          • ​Monochromats

      • ​Opponent-color theory
        

        • ​2 types of color-sensitive units
          

          • ​red green
            

          • ​blue yellow
            

        • ​neural level
          

        • ​afterimages

        • ​color deficiency
          

          • ​red&green
            

• ​Sensory coding
  

  • ​temporal pattern
    

  • ​number of neurons activated
    

• ​Audition

  • ​Stimuli

    • ​air-pressure change
      

  • ​Auditory system
    

    • ​Amplify and transmit the sound to the receptors
      

    • ​Transduce the sound into neural impulse
      

  • ​Theories

    • ​Temporal theory
      

      • ​low-frequency tones
        

      • ​time

    • ​Place theory
      

      • ​high-frequency tones
        

      • ​basilar membrance