Review, Urbach lecture

Adrienne Moore

3/4/2008

“Reality Science” – scientists don’t just conduct experiments

• The process actually involves:• Experimental design

• Writing/obtaining grants

• IRB approval (Institutional Review Board)

• Conducting the experiment

• Conference presentations (preliminary findings)

• Writing peer-reviewed journal publications

• Writing review chapters

Intro to Experimental Design

• What is an experiment?• An activity that “fiddles with” (manipulates)

an observable process and then observes what happens

• What is a good experiment?• An activity that manipulates an observable

process in a way that allows you to figure out the cause of the outcome and then observes what happens

Basic Elements of Good Experimental Design

• Independent Variable– Manipulated by the researcher

• Dependent Variable– Unknown, measured by the researcher

***we want to know whether manipulating the independent variable causes the dependent variable to change***

• Control Condition– The independent variable is *not* manipulated here

• Experimental Condition– The independent variable is manipulated here---------------------------------------------------------------------------------------------

• Confounds (bad)– Arise when more than one thing differs between the control and

experimental condition (which one causes the outcome?)

An Example

• I pick up the newspaper and read that a 23 million dollar class action law suit has been settled against the makers of Airborne! Someone claims there’s no good evidence that Airborne actually works. I am shocked, because I used Airborne last week and my cold cleared up, which proved to me that Airborne does help with colds. What do you think I did wrong?

• Did I do an experiment?– Yes, I fiddled with the natural process of developing a cold by

taking “medicine” and then observed what happened.

• Was it a good experiment?– No, though my cold did go away, I couldn’t be sure that Airborne

was the cause.

• What did it lack?– A control condition

• What might be an independent variable, a dependent variable, a control condition, and an experimental condition that could address the question “Does Airborne prevent colds from emerging”?– Independent – did you take Airborne, Yes (experimental

condition) or No (control condition)– Dependent – how many cold symptoms remained with

(experimental) and without (control) the manipulation

• Now I have an independent variable, a dependent variable, an experimental condition, and a control condition – is this a good experiment yet?

• Not really – too many confounds• “First principle of experimentation” (manipulate one

variable at a time, avoid confounds)• “First practical of experimentation” (the first principle is

very hard to achieve)• Good Advice:

– Try to turn confounds into independent variables– Increase sample size and then average your samples

Review, How to Read ERP Data (time, amplitude, electrode)…

…and EEG

Spectral data.(time,

frequency, power,

electrode)

Review Pineda slide

What is EEG?

• Electroencephalography:noninvasive method for measuring the brain at work with very good temporal precision

• EEG Spectral analysis:

• Asks where in the signal (at what frequency band) is there a lot of activity?

Review Viirre slide

EEG analysis

2 options -- Temporal domain :

Evoked Potential, ERP Always averaged

Frequency domain (spectral analysis) : ERSP, power (Pineda’s

approach) Either averaged or “single-

shot” ICA makes single shot

possible

Memory Performance ERP experiment

• 1. show subjects lists of related words and ask them to memorize them

• 2. after a delay, subjects perform old/new recognition task, using a list of related and unrelated new and old words

• 3. subjects will frequently believe a new word is old if it’s closely related to the old words (“memory intrusions”)

• 4. but there’s an ERP component associated with correct recognition memory -- it differs to old vs new words

• 5. and the ERP component differs to a new word even when the subject believes the word is old