Absence of SCRs

Absence of SCRs during events but unrelated SCR in the middle

If we run the SCR analysis on this subject’s data, we get one big massive SCR and otherwise nothing (until after the task ends). Remember to always cross-check other channels if strange events occur. In this case, we are also looking at the EMG signal (channel 11; muscle activity from the right forearm). You can see that there was muscle activity at the onset of the big SCR. We don’t know whether that was a big body movement, a sneeze, a cough, or a yawn or if the person got startled (e.g. unexpected noise, someone knocked on the door or similar → can always check for notes for this subject’s session on confluence). In any case, we need to exclude this subject from the analysis.

How do I know the data have sufficient quality to analyze?

In this example, the range of the signal is small (ca. 1.75-2.25 microsiemens for the visible signal range - compare to subject above peaking above 9 micro siemens). Remember, in the EDA preferences, you selected a baseline, threshold and a rejection percentage of amplitude height that will all determine whether a peak qualifies as an SCR. Therefore, we leave it up to the software to decide whether the fluctuations are large enough to report as an SCR. It is important to apply the same threshold to all subjects and data.

Partly usable with effort

In the following example, the signal is good until the last section of the task. In the focus area labeled “Rest5”, there are several signal artifacts. If you run the SCR analysis, markers for SCRs will show up on the artifacts, THESE NEED TO BE REMOVED. The reason this is ok in this particular case is that SCRs occur within a few seconds after an event, but not minutes after. Since these SCRs are not related to the (in this case) sigh, it is ok to delete them.

Real signal disturbance, do not use

In the following example, there are clear technical artifacts. This signal needs to be discarded, there is no way to rescue this.

This is the same file, just zoomed in around “Sigh2”