Resources: Getting Started
What is Baseline? How do I establish a baseline? For individuals? Multiple people?
Baseline is generally considered to be the average tonic level of an individual during rest conditions and in the absence of any discrete environmental event/external stimulus.
Standard practice – based on years of studies limited to labs, and usually for a lab session of less than an hour to gather data for scientific research papers – is to have the person wear the EDA sensor for 15 minutes of rest prior to any tasks or measurements. During this period the subject should be asked to sit comfortably, hold still and relax. If they succeed in truly relaxing, then ideally the signal drops to be low and smooth, and once it does, then the lowest values are usually averaged to provide a baseline.
Fig.1 Activating task, followed by rest to get a baseline. The task was to count backwards from a 4 digit number by 7s as fast as possible and as accurately as possible.
There are several problems with the traditional baseline approach: Sometimes people cannot relax before or during a lab task – they might have anticipatory arousal, they might have anxiety being in an unfamiliar space not knowing exactly what they are going to be doing, and they might be uneasy being watched. They might have to use the restroom. They might suddenly remember that they promised a friend they would meet at that time. They might need more than 15 minutes to relax. In all these cases, while they may look like they are calm and relaxing on the outside, their levels may be higher than a true baseline.
The Q sensor makes long-term EDA measurement practical, so now you can get a 24/7 baseline and measure what a person’s truly lowest tonic skin conductance levels are over daily life. This solves many of the problems that previously existed with short-term lab-only measurements of EDA baselines. The best way to get a baseline now is to measure long-term, and look for the lowest smooth period of skin conductance where there is no physical movement (where the accelerometer data is smooth), and where the temperature is clearly body temperature.