This lesson is centered around reading and performing simple processing on a sample experiment data set. This document describes the data format and variables as well as the experiment that generated the data set.
The data set is provided in a CSV file with five columns representing the following variables.
Type Identifier
Description Arbitrarily assigned unique identifier for each subject
Values Positive consecutive integers starting at 1
Type Group/Between-subjects
Description High vs. Low working memory capacity based on OSPAN score
Values
High= at or above median OSPAN score of 55Low= below median OSPAN score of 55
Type Repeated/Within-subjects
Description Operation span score (higher the score, higher the working memory capacity)
Values Positive Integers (number of words recalled)
Type Repeated/Within-subjects
Description Amplitude (microvolts) of electrical brain signal to distracting sounds in EASY condition
Values Decimal numbers (microvolts)
Type Repeated/Within-subjects
Description Amplitude (microvolts) of electrical brain signal to distracting sounds in HARD condition
Values Decimal numbers (microvolts)
There is behavioral evidence that individuals with better short term (working) memory are better able to focus attention and withstand distraction.
We wanted to find out if this behavioral difference is due to differences in how our brains process distracting information.
- Measured all subjects' operation span (index of working memory capacity). Operation Span test presents alternating math problems with letters, and subjects are to recall letters in correct order when prompted
- A median OSPAN score of 55 was used to divide subjects into "High" and "Low" working memory capacity groups
- All subjects completed an auditory attention task in which they listened for a target tone that was played amid other nontarget tones and distracting sounds.
- They each completed this task under two conditions: Easy vs. Hard
- In the easy condition, target and nontarget tone frequencies were far enough apart to be easily distinguishable (see table below)
| Easy Hard
============|=============================
Target | 1000Hz 1000Hz
Nontarget | 500Hz 950Hz
Distracter | White Noise White Noise
We used EEG to measure electrical brain activity (amplitude in microvolts) associated with processing each type of sound (target, nontarget, distracter).
The dataset here shows amplitude (in microvolts) of brain activity associated with processing the distracter sound.
This neural activity occurred ~100ms after the presentation of the distracting sound, and was picked up by electrode placed on the scalp at the middle-top of forehead (index of frontal lobe activity).
In general, this brain response is an index of distraction; the larger the amplitude, the more the person was distracted by the white noise.
Main effect of task condition
larger amplitudes under easy condition → suggests more distraction when task is easy (i.e. does not fully engage attention)
Main effect of subj group
larger amplitudes for low working memory group → suggest low working memory group more easily distracted/less focused
Yurgil K.A. & Golob E.J. (2013). Cortical potentials in an auditory oddball task reflect individual differences in working memory capacity. Psychophysiology, 50(12), 1263-1274. PMID: 24016201