Experiment Design 4: Theoretical + Operational Def’ns

1. Experiment Design 4:Theoretical + Operational Def’ns Martin Ch. 7

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

3. Valid, reliable Valid, not reliable Not valid, reliable Not valid, not reliable Measure Reliability vs. Validity

4. 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?

5. 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!)

6. Example experiments • Intelligence & age • Classroom size & learning

7. Indirect measures:Behavioral 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

8. Even more indirect measures: Physiological measures • Examples: • GSR, EEG, PET, fMRI, MEG • Timing: • Timing of activation = timing of processing • Activity: • More activation = more processing

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

10. 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)

11. PET Images are taken at many different slices across the brain

12. An example PET study

13. An fMRI scanner • Very loud and produces claustrophobia • Therefore, also some questions of poor external validity

14. 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.

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

16. EEG & ERP

17. 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.

18. Event-Related Potentials (ERP) • Fast changes in EEG in response to a stimulus

19. 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, don’t know if have perfect targeting ability yet • Also, because it is repetitive, don’t have timing information

20. 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