The Cognitive Science Approach

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Chapter 2

• The Cognitive Science Approach

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Guiding Principles

• Our metatheory is the information processing
  approach
• Cognition equals the coordinated operation of
  active mental processes within a multi component
  memory system.

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Seven Themes of Cognition

• Attention
• Automatic versus conscious processing
• Data-driven versus conceptually driven processing
• Representation
• Implicit versus explicit memory
• Metacognition
• Brain

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Seven Themes of Cognition
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Time and Accuracy Measures

• Reaction Time
• A measure of the time elapsed between some
  stimulus and the persons response to the
  stimulus (RT).
• Almost always measured in milliseconds.

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Vocal Reaction Times to Multiplication Problems
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Time and Accuracy Measures

• Accuracy
• Often we are interested instead in some measure
  of peoples accuracy.
• The earliest use of accuracy as a measure of
  mental processes was the seminal work by
  Ebbinghaus, published in 1885.

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Serial position curves, showing the decrease in
accuracy at the end of the list when 0, 10, or 30
s of backward counting intervenes between study
and recall.
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Analogies

• The channel capacity analogy
• Like a telephone wire, humans are
  limited-capacity information processors.
• The computer analogy
• Human information processing may be similar to
  the way computers work.

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The Standard Theory

• The Atkinson and Shiffrin Model of Human Memory
• Three memory components sensory memory,
  short-term memory, and long-term memory.

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The Standard Theory of Human Information
Processing

• The Atkinson and Shiffrin Model

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Process Models

• A hypothesis about the specific mental processes
  that take place when a particular task is
  performed.

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The Lexical Decision Task

• Yes or no, do the following letter strings form
  valid English words?
• 1) Robin _____
• 2) Manty _____
• 3) Nurse ______
• 4) Trock ______

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A Process Model of the Lexical Decision Task

• Encode
• Search
• Decide
• Respond

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A Process Model of the Lexical Decision Task
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Assumptions of Strict Information Processing

• Sequential stages of processing
• Independent and non-overlapping stages of
  processing

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Difficulties of Strict Information Processing

• Solid evidence exists for parallel processing,
  e.g. Typing
• Context effects, e.g. Semantic Priming
• Not useful for studying complex cognition (e.g.,
  problem solving tasks) and tasks with slower RTs

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Context Effects

• Count the number of Fs in the following
  sentence (Warning This is harder than it looks)
• Finished files are the result of years of
  scientific study combined with the experience of
  many years.

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Top-Down Processing

• AKA Conceptually-driven processing
• When existing context has an influence on earlier
  or simpler forms of mental processes
• In the finished files example, reading is so
  automatic that youve learned to ignore function
  words like of-- an example of top down
  processing.

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Updating the Standard Theory
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Neurocognition

• Dissociation A disruption in one component of
  memory but no impairment of another.
• Simple versus double dissociations
• Lack of dissociation an association

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Neurons
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Neuron Anatomy

• Soma
• Nucleus
• Dendrite
• Myelin Sheath
• Aborizations
• Terminal Buttons
• Axon
• Axon Hillock

• Receptor cells / sensory neurons
• Effector cells / motor neurons
• Interneuron
• Synapse
• Neurotransmitters

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Brain Anatomy
TOP
FRONT

• BACK

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Brain AnatomyLower Brain Structures
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Brain Anatomy (cont.)

• Three other subcortical (below the neocortext)
  structures are especially important to
  neurocognition
• thalamus the gateway to the cortex almost
  all messages entering the cortex come through
  the thalamus
• corpus callosum the primary bridge across
  which messages pass between the left and right
  halves or hemispheres of the neocortex
• hippocampus an internal brain structure
  strongly implicated in the storing of new
  information into long-term memory

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Four Lobes of the Neocortex
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Brain Anatomy

• Corpus Callosum
• Thalamus
• Hypothalamus
• Pituitary
• Hippocampus
• Amygdala
• Medulla

• Cerebral Cortex
• Frontal Lobe
• Parietal Lobe
• Occipital Lobe
• Temporal Lobe

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Principles of Function

• Contralaterality
• The receptor and control centers for one side of
  the body are in the opposite hemisphere of the
  brain.

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Brain Anatomy
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Principles of Function

• Hemispheric Specialization
• Different brain functions tend to rely more
  heavily on one hemisphere or the other.
• Example The left hemisphere controls language
  for most right-handed people.

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The two hemispheres of the brain are connected by
a band of fibers called the corpus callosum
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Split-Brain Patients

• Severed corpus callosum to stop epileptic
  seizures
• No obvious problems at first
• Laboratory testing revealed some problems
• Remember

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Left visual field projects to right hemisphere R
ight visual field projects to left hemisphere
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(No Transcript)
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Split Brain Research

• Sperry -- severed corpus callosums of people with
  severe epilepsy.
• How does Sperrys research support the idea that
  the left hemisphere processes language?

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Split-Brain Research and Lateralization

• Research on split-brain patients
• Principle of lateralization

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Methods of Investigation

• Lesions Used by Sperry the site and extent of
  the brain lesion are important guides to the kind
  of disruption in behavior that is observed and
  vice versa.
• Direct Stimulation Pioneered by Penfield the
  patient in brain surgery remained conscious
  during surgery and was administered minute
  electrical charges to the exposed brain, thus
  triggering very small regions.

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Exposed cortex of one of Penfields patients
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Methods of Investigation (cont.)

• Imaging Technology
• Magnetic Resonance Imaging (MRI) Gives clear
  pictures of the structure of the brain.
• Functional MRI Image shows regions of the brain
  with heightened neural activity, with different
  colors reflecting high or low levels of blood
  flow, oxygen uptake, and the like.

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Methods of Investigation (cont.)

• Electrocephalograms (EEG) Electrodes are
  attached to the subjects scalp, and the device
  records the patterns of brain waves.
• Event-Related Potentials The momentary changes
  in electrical activity of the brain when a
  particular stimulus is presented to the subject.

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Event Related Potential (ERP)
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Parallel Distributed Processing
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Neural Net Models

• AKA Parallel distributed processing, or
  connectionist models.
• Contain a system of interconnected nodes, with
  knowledge represented by the interconnections
  between units.
• Processing in the model is massively parallel.

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Brain vs. Computer

• 100 billion neurons (1012)
• Clock speed 1KHz
• of processors ???
• Equivalent MIPS 100 million (1014)

• 100 million transistors (109)
• Clock speed 3 GHz (3x1012)
• of processors 2
• Equivlent MIPS 10,000 (1011)

Brain 1000x faster (for now)
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Summary of Major Topics Covered in Chapter 2

• Measuring information processing
• The information processing approach
• The modern cognitive approach
• Neurocognition
• Neural Net Models