There are two main components to the overall complex referred to as EDA. One component is the general tonic-level EDA, which relates to the slower acting components and background characteristics of the signal (the overall level, slow climbing, slow declinations over time). The most common measure of this component is the Skin Conductance Level (SCL), and changes in the SCL are thought to reflect general changes in autonomic arousal.
The other component is the phasic component and this refers to the faster changing elements of the signal - the Skin Conductance Response (SCR). The SCR threshold has historically been set at around 0.05 uS, however, it’s not uncommon to consider a minimum amplitude that varies from 0.01 to 0.05uS, and the choice will be influenced by experimental conditions.
The EDA reading is influenced by:
- the length of the recording: coupling of the electrodes with the skin could take around 10/15 minutes
- the material of the electrodes
- the position of the electrodes on the body
- the environmental conditions during the recording (temperature and humidity of the room).
For further information regarding the EDA signal, please refer to What should I know to use EDA data in my experiment.
Below are some examples of expected EDA values with their graphic representation on the E4 Connect portal.
a) Example of a low tonic phase, with an insignificant phasic activity (45-minute long segment)
b) Example of low tonic phase with a phasic activity (35-minute long segment)
c) Example of a low tonic phase with a significant phasic activity (2.5-hour long segment)
d) Example of a high tonic phase with low phasic activity (4-minute long segment)
e) Example of a high tonic phase with significant phasic activity (1-hour long segment)