sensation and perception

• In order 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 is the process of our sensory organs receiving information from the environment and then sending it to the relevant parts of the brain.
• The 3 processes of vision sensation are reception, transduction, and transmission
• process of reception:

  Light enters the eye through the cornea and passes through the pupil.

  The lens then focusses the light on the retina. The retina contains photoreceptors – which are light sensitive cells called rods and cones.
• process of transduction:

  The electromagnetic energy we know as light energy, is converted by the rods and cones into electrochemical nerve impulses.

  This allows the visual information to travel along the fibres of the optic nerve to the brain.
• process of 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 visual perception continues.
• Optic nerve: the two tracts of neurons that transmit visual information from the eyes to occipital lobes of the brain.
• Receptive fields: a particular region of the visual space

  When your retina identifies visual stimuli, it passes this information via rods or cones to bipolar cells and then to the retinal ganglion cell.
• 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.
• the three processes of perception are selection, organisation and interpretation. They are specific to vision.
• Selection:

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

  The image is broken up by specialised cells called feature detectors
• Organisation:

  Our visual cortex in the brain recognizes information so that we can make sense of it
• visual perception principles of organisation:

  • perceptual constancies
  • Gestalt principles
  • depth cues
• Interpretation:

  • the visual stimulus is given meaning.
  • The temporal lobes identify the stimulus by comparing incoming information with information already stored in memory.
  • Past experiences, motives, values and context help us to understand what we are looking at by contributing to our perceptual set.
  • 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
• prosopagnosia: Patients who have damage or tumours in parts of the temporal lobe may be unable to recognise an object or a familiar face
• Attention: the process of focusing on specific stimuli or aspects of the environment whilst ignoring and excluding others.
• Divided attention: refers to the ability to distribute our attention so that two or more activities may be performed simultaneously.
• Our ability to multitask depends on how much conscious effort is required for the various tasks in which we are engaged. This also depends on the similarity and complexity of the tasks, as well as how accomplished or experienced we are at doing them.
• Research findings indicate that our perceptual systems can more competently perform tasks requiring divided attention when the tasks are similar, not complex, and well-known and do not demand considerable mental effort.
• Selective attention: involves choosing and attending to a specific stimulus whilst at the same time excluding other stimuli.
• factors that determine whether we will attend to a particular stimulus:

  • important or meaningful
  • physiological state
  • motives
  • Past experiences
  • Novel