Exam revision: memory

• Sensation


  The process of your sensory organs receiving information from the environment and then sending it to the relevant parts of the brain
• Perception


  The process of interpreting and organising sensory information
• Processes of sensation


  1. Reception

  2. Transduction

  3. Transmission
• For us to receive a sensation, the appropriate stimulus energy (absolute threshold) must reach the sense organ and this must be at the level sufficient 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
• Processes of sensation (specific to vision)


  1. Reception

  2. Transduction

  3. Transmission
• Reception


  Light enters the eye through the cornea, passes through the pupil, and the lens focuses the light onto the retina
• Transduction


  The electromagnetic energy that we know as light energy, is converted by the rods and cones into electromagnetic nerve impulses
• 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
• Retinal ganglion cell


  A type of neuron that is located near the surface of the retina; visual information from the photoreceptors is received by the retinal ganglion cells
• Transmission


  The rods and cones send the nerve impulses along the optic nerve to the primary visual cortex in the occipital lobes, at the very back of the brain where specialised receptor cells respond as the process of perception continues
• Photoreceptors


  • Detect visual stimuli
  • Rods (125000000 in each eye) are photoreceptors that are particularly sensitive to black and white, and we typically use these at night
  • Cones (6500000 in each eye) are involved in providing clear colour vision and rely on bright light to function
• Processes of perception

  1. Selection

  2. Organisation

  3. Interpretation
• Perception


  Three processes of perception- selection (feature detectors), organisation and interpretation (both based on visual perception principles)- are specific to vision
• Selection


  1. Millions of stimuli enter the eye and it is impossible to process them all at once, so we are selective about what we give our attention to

  2. At this stage of the process, the image is broken up by specialised cells called feature detectors (cells in the optic nerve and primary visual cortex that individually respond to lines of a certain length, angle or direction to break up an image for visual perception)
• Organisation


  1. Our visual cortex in the brain recognises information so that we can make sense of it

  2. We do this by using the following visual perception principles: Perceptual constancies, Gestalt principles, Depth cues

  3. Once the image is reassembled using these principles, it travels along two pathways simultaneously to the temporal lobe to identify the object and to the parietal lobe to judge where the object is in space
• Interpretation


  1. This is the process whereby the visual stimulus is given meaning

  2. The temporal lobe identifies the stimulus by comparing incoming information with information already stored in memory

  3. Past experiences, motives, values, and context help us to understand what we are looking at by contributing to our perceptual set

  4. While information is sent to the temporal lobes it also travels to the parietal lobes which assist in judging where the object is in space
• Patients who have damages or tumours in parts of the temporal lobe may be unable to recognise an object or a familiar face (prosopagnosia)
• Patients who have damage to their parietal lobes will be able to recognise an object, but they may constantly bump into furniture or misjudge picking up their knife and fork
• Attention


  Selective and divided attention as seen in the Cocktail party effect
• Cherry used the simple method of playing back two different messages at the same time to people under a variety of conditions

  1953
• Cherry discovered how good we are at filtering what we hear which is how we overcome the cocktail party problem
• Participants in Cherry's experiment


  1. Close their eyes

  2. Concentrate hard
• First set of experiments on the cocktail party effect


  1. Play back two different messages voiced by the same person through both ears of headphones

  2. Ask participants to 'shadow' one of the two messages they were hearing by speaking it out loud

  3. Ask participants to write down one of the two messages
• When doing this task, participants could, with effort, and while hearing the clips over and over again, separate one of the messages from the other with the two voices presented together as though the same person were standing in front of you saying two completely different things at the same time
• Pushing participants further, Cherry found he could confuse listeners, but only by having both messages consist entirely of nonsensical platitudes
• Only then were participants unable to pick apart one message from the other
• Cocktail party effect


  Our ability to separate one conversation from another
• Classic study carried out by Colin Cherry

  1. Feed one message to the left ear and one to the right ear

  2. Both messages voiced by the same speaker
• Many were surprised how easily and accurately they could tune in to either of the messages and even shift their attention back and forth between the two
• What participants were experiencing here seems much closer to most people's experience of the cocktail party phenomenon
• At a party, people are arrayed all around us and their conversations come from various different directions
• Encoding


  Conversion of sensory information into a usable form so that it can be neurologically represented and 'placed' (stored) into memory
• Storage


  Retention of the encoded information over time. We store the information in an organised way to make it easier for us to recover the information when we need it
• Retrieval


  The process of getting information back from memory so that we can use it. Retrieval relies on using the right cues so that we can get the correct location in our brain
• memory is spread out over a huge area of cells through different areas of our brain
• Storage is a dynamic process where human memories change over time. They are rough copies rather than exact replicas of information
• Atkinson-Shiffrin Multi-store model of memory (1968)


  Represents memory as consisting of three separate stores called sensory memory, short-term memory, and long-term memory
• Sensory Register/memory


  • Duration
  • Capacity
  • Encoding