Sensation&Perception

• Absolute threshold


  The appropriate stimulus energy must reach the sense organ at a sufficient level to activate the sense receptors
• Sensation examples


  • Hearing the ticking of a watch 6 metres away
  • The touch of a wing of a fly falling on your cheek
• Sensation


  The process of your sensory organs receiving information from the environment and then sending it to the relevant parts of the brain
• Processes of sensation (specific to vision)

  1. Reception

  2. Transduction

  3. Transmission
• Reception


  1. Light enters the eye through the cornea

  2. Then it passes through the pupil

  3. The lens then focuses the light onto the retina

  4. The retina contains photoreceptors (rods and cones)
• Photoreceptors


  Light-sensitive cells called rods and cones
• Transduction


  1. The electromagnetic energy (light energy) is converted by the rods and cones into electromagnetic nerve impulses

  2. Visual information travels along the fibers of the optic nerve to the brain
• Optic nerve


  The two tracts of neurons that transmit visual information from the eyes to the occipital lobes of the brain
• Receptive fields


  A particular region of the visual space
• Transmission


  1. Rods and cones send nerve impulses along the optic nerve to the primary visual cortex

  2. Specialised receptor cells respond as the process of visual perception continues
• Rods


  Photoreceptors sensitive to black and white, typically used at night (125,000,000 in each eye)
• Cones


  Photoreceptors involved in providing clear colour vision, rely on bright light to function (6,500,000 in each eye)
• Perception


  The process of selection, organisation, and interpretation of visual stimuli
• Processes of perception


  1. Selection

  2. Organisation

  3. Interpretation
• Selection


  The process of being selective about what we give our attention to
• Feature detectors


  Cells in the optic nerve and primary visual cortex that respond to lines of a certain length, angle, or direction
• Organisation


  The visual cortex recognises information to make sense of it using visual perception principles
• Visual perception principles


  • Perceptual constancies
  • Gestalt principles
  • Depth cues
• Interpretation


  1. The process whereby the visual stimulus is given meaning

  2. The temporal lobe identifies the stimulus by comparing incoming information with stored information
• Past experiences, motives, values, and context contribute to our perceptual set
• Patients with damage to the temporal lobe may be unable to recognise an object or familiar face (prosopagnosia)
• Patients with damage to their parietal lobes may recognise an object but misjudge spatial interactions
• Cocktail party effect


  The ability to focus on a single conversation in a noisy environment
• Process of memory


  1. Encoding

  2. Storage

  3. Retrieval
• Multi-store model of memory

  A model proposed by Atkinson and Shiffrin
• Sensory register


  Duration, capacity, and encoding of sensory information