Module 3 & 6

• Perception


  Set of processes by which we recognize, organize, & make sense of the sensations we receive from environmental stimuli
• Distal object


  • Object in the external world
• Informational medium


  • Event/pattern; stimulus that comes into contact with appropriate sensory receptor (e.g. light waves)
• Proximal stimulation


  • When information is absorbed by the sensory receptor (e.g. eyes, retina)
• Perceptual object


  • Reflects the properties of the external world; what the person perceives
• Sensation


  Focus on qualities of stimulation (e.g. Is the shade of red brighter than the red of an apple?)
• Perception


  Focus on identity & form, pattern, & movement (e.g. Is that red thing an apple?)
• Cognition


  Information is used to serve further goals (e.g. Is that apple edible?)
• Sensory Adaptation


  • We never can experience exactly the same set of stimulus properties we have experienced before
  • Variation is necessary for perception, as receptor cells adapt to constant stimulation by ceasing to fire until there is a change in stimulations
  • Through sensory adaptation, we may stop detecting the presence of a stimulus
  • Ensures sensory information is constantly changing
• Ganzfeld


  Unstructured visual field<|>When eyes are exposed to uniform field of stimulation, one will stop perceiving that stimulus after a few minutes
• Visual pathway


  Path the visual information takes from entering the perceptual system through eyes to being completely processed
• Two visual pathways (What/Where hypothesis)

  • Dorsal pathway - towards parietal lobe; where pathway; process location & motion information
  • Ventral pathway - descends to temporal lobe; what pathway; process color, shape, & identity of visual stimuli/objects
• Bottom-up theories


  Perception starts with the stimuli taken in through the eye<|>Data-driven (stimuli-driven)
• Gibson's Theory of Direct Perception


  • All we need is information from sensory receptors/context
  • Ecological perception - environment supplies us with all information we need for perception; do not need higher cognitive process to mediate between our sensory experiences & perceptions
  • Perception is based on our analysis of the stable relationships among features of objects & settings in the real world, we directly perceive our environment: Ecological Model
  • Focuses on perception as it occurs in the everyday world (needs context) rather that labs where less context is needed
• Template Theories


  • We have stored in our minds myriads sets of templates
  • Templates - highly detailed models for patterns we might recognize by comparing it to our set of templates
  • Then choose the exact template that perfectly matches what we observe
  • Chunk-based theory - expertise is attained by acquiring chunks off knowledge in long-term memory that can later be assessed for fast recognition
  • Template matching in our everyday lives - barcode/QR
  • Problem - only one exact match will do
• Feature-Matching Theories


  • We attempt to match features of a pattern to those stored in memory, rather than matching a whole pattern to a template
  • The Pandemonium Model (Oliver Selfridge) - "Pandemonium" (very noisy, chaotic place in hell) metaphorical "demons" with specific duties receive & analyze the features of a stimulus
  • Four Kinds of Demons: Image demons, Feature demons, Cognitive demons, Decision demons
• Global Features


  Give form to the overall shape of a given pattern
• Local Features


  Small-scale/detailed aspects of a given pattern
• Global Precedence Effect


  • Required to identify stimuli at the global level, whether local feature match or not
  • Response is quicker if global features agreed with local ones
• Local Precedence Effect


  • If widely spaced, local features are easier to identify than global ones, and it interferes with identifying the global ones
  • If close together, it's harder to identify local stimuli inconsistent with the global stimuli
• Recognition-by-Components (RBC) Theory / Structural Depiction Theory (Irving Biederman)


  • Explains ability to perceive 3-D objects with the help of simple geometric shapes called geons (geometrical ions)
  • Can be used to build basic shapes & myriad basic objects
  • Simple & viewpoint-invariant
  • Easily recognized despite visual noise
  • Recognize objects by observing edges & decomposing them into geons; which can also be recomposed into alternative arrangement
  • Limitations - does not explain how we recognize particular objects/faces
• Top-down theories


  Perception is driven by high-level cognitive process, existing knowledge, & prior expectation that influence it<|>Perceiver builds (constructs) a cognitive understanding (perception) of a stimulus; uses sensory information as foundation for structure but also uses other sources of information
• Intelligent Perception


  Higher-order thinking plays an important role in perception<|>During perception, we quickly form and test many hypothesis regarding percepts: What we sense (sensory data), What we know (knowledge stored in memory), What we can infer (using high-level cognitive processes)
• Concepts supported by top-down processing

  • Context Effects - influences of the surrounding environment on perception; context makes recognition better
  • Configural-superiority effect (Bar & Pomerantz) - objects presented in certain configurations are easier to recognize than the those presented in isolation
  • Object Superiority Effect - target line that forms a part of a drawing of a 3-D object is identified more accurately than a target that forms a part of a disconnected 2-D pattern
  • Word Superiority Effect - it is easier to identify a single letter if the string makes sense & forms a word instead on being just a nonsense sequel of letters
• Perception and Intelligence


  We perceive in terms of the expectations & other cognitions we bring to our interaction with the world<|>Both processes interact in the formation of our beliefs
• • Downside of the two approaches: Extreme top-down position would underestimate the importance of sensory data
  • We frequently form hypothesis & expectancies that inadequately evaluated the sensory data available
  • An extreme bottom-up position would not allow for any influence of past experience/knowledge
• Perception of objects & forms

  • Viewer-centered representation - individual stores the way the object looks to him or her: what matters is the object's appearance to the viewer
  • Object-centered representation - individual stores a representation of the object, independent of its appearance to the viewer
  • Landmark-centered representation - information is characterized by its relation to a well-known/prominent item
• Pattern Recognition Systems (Martha Farah)


  • Feature analysis system - recognize parts of objects; assemble them into wholes
  • Configurational system - recognize larger configurations (face recognition)
• Fusiform Gyrus


  Face recognition happens in this area in the temporal lobe; brain area responds intensely when we look at faces but not when we look at objects
• Deficits in perception

  • Agnosia - inability to recognize & identify objects/people
  • Prosopagnosia - inability to recognize faces (even own); ability to recognize objects is intact
  • Simultagnosia - normal visual fields, yet act blindly; perceives only one stimulus at a time
  • Optic ataxia - impairment in the ability to use visual system to guide movement; difficulty reaching for items
• Attention


  Concentration of mental energy used to process incoming information; selective, limited
• Consciousness


  Awareness of one's environment and one's own existence, sensations, and thoughts
• Disruption of "what" pathway

  1. Agnosia - inability to recognize & identify objects/people

  2. Prosopagnosia - inability to recognize faces (even own); ability to recognize objects is in tact

  3. Simultagnosia - normal visual fields, yet act blindly; perceives only one stimulus at a time
• Disruption of the "how" pathway

  Optic ataxia - impairment in the ability to use visual system to guide movement; difficulty reaching for items
• Attention


  Concentration of mental energy used to process incoming info; selective, limited, or both conscious & preconscious; allows us of limited mental resources & paves way for memory processes
• Consciousness


  State of being aware; both feeling of awareness & the content of awareness
• Four Main Functions of Attention

  • Signal detection and vigilance
  • Search
  • Selective attention
  • Divided attention
• Signal Detection Theory


  How people pick out the few important stimuli when they are embedded in a wealth of irrelevant, distracting stimuli
• Vigilance


  Attending to a set of stimuli over a length of time to detect target signal
• Search


  1. Feature Search - scan the environment for the feature; distracters play little role

  2. Conjunctive Search - looking for a particular combination of features; with distracters