Data and Matlab code for my blog post on ERP differences https://garstats.wordpress.com/2016/04/02/simple-steps-for-more-informative-erp-figures/

The file erp_differences.m generates the main figures, providing you have installed the toolbox limo eeg, available on github. https://github.com/LIMO-EEG-Toolbox/limo_eeg

erp_differences uses two files, both containing data from one electrode only. I used electrode B8 from the Biosemi 128-channel layout. It is a right posterior electrode which tends to record the largest face responses across participants. No bad trial rejection was done.

• erps.mat contains the variable erps, a 20 participants x 2 conditions cell array. Each cell contains a matrix with dimensions 1 electrode x 451 time points x 192 trials. The 451 time points correspond to a 500 Hz sampling from -300 ms to 600 ms post-stimulus onset.

• erpm.mat contains the variable erpm, which is a matrix of 451 time points x 20 participants x 2 conditions of mean averages across trials.

The file fake_erp_differences.m demonstrates a few examples of fake ERPs and their differences. The point is that it is sometimes difficult to form a mental image of the difference from the original conditions alone.