Standard deviation (std): standard deviation of the sample
Standard error, or standard error of the mean (sem), is the standard deviation of the mean. \(sem=std/\sqrt{N}\)
Most errorbars in scientific publications refer to standard error. Quite often a T-test is accompanied to show the effect is significant. This makes sense if they try to compare if the mean is different. Sometimes – quite often in neuroimage – while the mean is significantly different, it is almost impossible to tell the difference on the individual level (or classify individual observation). If the authors used standard deviation, the errorbars would have been huge and figures got ugly.
