Theoritical & Operational Definitions

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    10-Apr-2018
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    Experiment Design 4:

    Theoretical + 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 a lso representative

    Cost and timeeffective

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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 theface 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 measures:

    Behavioral measures Reaction time

    More time = more processing orless

    automatic

    Need largeN to get reliable data

    Choice & errors

    Harder = more processing orlessautomatic

    Speed-accuracy tradeoffs

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    Even more indirect measures:

    Physiological measures Examples:

    GSR, EEG, PET, fMRI, MEG

    Timing:

    Timing ofactivation = timing ofprocessing

    Activity:

    More activation = more processing

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    Direct stimulation

    Apply smallelectricalcharge to brain

    area

    Ask patient what happens

    Seelights or hear sounds, etc?

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    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 magneticchanges due to changes

    in blood oxygen levels (good timing info)

    EEG & ERP

    Track brain waves (best timing info)

    Imaging

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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

    Veryloud and produces claustrophobia Therefore, also some questions ofpoor

    external validity

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    An example fMRI study

    Subjects viewed a face on a computer

    monitorfor 3 seconds, held theface in

    memory (with no visual stimuli)for an 8second pause, and then viewed a second

    facefor 3 seconds. They pressed a button to

    indicate whether or not thefaces matched.

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    Impose fMRI on top ofMRI structural

    Use subtractive logic

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    EEG & ERP

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    Data gathered from EEG

    ALPHAWAVES, brought on by

    unfocusing one's attention, have

    relatively large amplitude and

    moderate frequencies.

    BETAWAVES, 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 magneticstimulation

    Produce a repeating magnetic disruption in

    one area of the brain to temporally disruptits function

    Allows forcausal inference

    But can causeepileptic seizures

    Also, dont know ifhave perfect targeting

    abilityyet

    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 normalfunctions

    Good localization and/or

    timing info

    rTMS

    Can establish causality

    Damage temporary

    Con

    Lesions Normal patients?

    Poor localization

    Direct stimulation

    Damagecells?

    Bigger patterns?

    Imaging

    Causal?

    Subtractivelogic?

    rTMS

    Seizures?

    Poor timing information

    Localization not clear