Experiment Design 4: Theoretical Operational Defns

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Experiment Design 4Theoretical Operational
Defns

• Martin Ch. 7

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Operational Definitions

• Select an operational definition that is
• Reliable
• Valid
• Likely to produce an effect
• But also representative
• Cost and time effective

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Measure Reliability vs. Validity

• Valid, reliable
• Valid, not reliable

• Not valid, reliable
• Not valid, not reliable

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Reliability

• Test-retest
• Same score again?
• Alternative-form
• Same score on similar test?
• Split-half
• Same score on even and odd items?
• Inter-rater
• Same score assigned by different raters?

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Construct (measure) validity

• Face
• Sounds plausible on the face of it?
• Content
• Content details seem appropriate?
• Predictive
• Predicts things that it should predict?
• Concurrent
• Correlated with things that should be related?
  (but not too highly!)

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Example experiments

• Intelligence age
• Classroom size learning

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Indirect measuresBehavioral measures

• Reaction time
• More time more processing or less automatic
• Need large N to get reliable data
• Choice errors
• Harder more processing or less automatic
• Speed-accuracy tradeoffs

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Even more indirect measures Physiological
measures

• Examples
• GSR, EEG, PET, fMRI, MEG
• Timing
• Timing of activation timing of processing
• Activity
• More activation more processing

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Direct stimulation

• Apply small electrical charge to brain area
• Ask patient what happens
• See lights or hear sounds, etc?

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Imaging

• Computerized tomography (CT scan)
• See brain regions (no timing info)
• Positron Emission Tomography (PET)
• Track heightened brain flow activity using
  radioactive isotope (slow timing info)
• Functional Magnetic Resonance Imaging (fMRI)
• Track magnetic changes due to changes in blood
  oxygen levels (good timing info)
• EEG ERP
• Track brain waves (best timing info)

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PET
Images are taken at many different slices across
the brain
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An example PET study
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An fMRI scanner

• Very loud and produces claustrophobia
• Therefore, also some questions of poor external
  validity

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An example fMRI study

• Subjects viewed a face on a computer monitor for
  3 seconds, held the face in memory (with no
  visual stimuli) for an 8 second pause, and then
  viewed a second face for 3 seconds. They pressed
  a button to indicate whether or not the faces
  matched.

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• Impose fMRI on top of MRI structural
• Use subtractive logic

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EEG ERP
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Data gathered from EEG
ALPHA WAVES, brought on by unfocusing one's
attention, have relatively large amplitude and
moderate frequencies.
BETA WAVES, the result of heightened mental
activity, typically show rapid oscillations with
small amplitudes.
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Event-Related Potentials (ERP)

• Fast changes in EEG in response to a stimulus

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Hot off the presses rTMS

• Repetitive transcranial magnetic stimulation
• Produce a repeating magnetic disruption in one
  area of the brain to temporally disrupt its
  function
• Allows for causal inference
• But can cause epileptic seizures
• Also, dont know if have perfect targeting
  ability yet
• Also, because it is repetitive, dont have timing
  information

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• Pro
• Lesions
• Can establish causality
• Direct stimulation
• Can establish causality
• Excellent localization
• Imaging
• Study normal functions
• Good localization and/or timing info
• rTMS
• Can establish causality
• Damage temporary

• Con
• Lesions
• Normal patients?
• Poor localization
• Direct stimulation
• Damage cells?
• Bigger patterns?
• Imaging
• Causal?
• Subtractive logic?
• rTMS
• Seizures?
• Poor timing information
• Localization not clear