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When measuring a particular phenomenon or cognitive state, it is interesting to use multiple measures. This allows you to inspect the similarity and differences of these measures, and serves as an indication of the validity of the measures. This is also referred to as triangulation.

In my study, I will measure workload with two systems that measure galvanic skin response (GRS) and two systems that measure heart rate variability (HRV). Not all systems allow for reliable time-stamping, however, making it difficult to synchronize the different systems' recordings. In order to triangulate the data, I must know how the time-lines overlap. Currently, the best approach is to start the System1, and then, with a stopwatch, measure the time it takes to start System2. Then, you can ignore/remove the data of System1 for that period of time and the data is lined up.

As an alternative I though to elicit a clear physiological response that would show in each system (by for example scaring the people or, less favorable, giving people electrical shocks). The goal is to have a physiological response that is distinguishable form any normal HRV or GSR response. Is there a reliable way to elicit and identify such a response in HRV or GSR?

I want thus that the HRV/GSR-response can be used as a "start of the experiment" marker or trigger that is recorded in each system. This way, I do not have to worry about synchronization until the analysis of the data.

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  • $\begingroup$ Just to clarify: are you pursuing the synchronization of different recording hardware systems? Or are you funneling all digitized data into one database? Could you clarify your setup? $\endgroup$ – AliceD♦ Oct 4 '16 at 10:00
  • $\begingroup$ @Christiaan I want to synchronize the systems. The time-marker is thus used as a "start of the experiment" marker. This way, I do not have to worry about synchronization until the analysis of the data. I've rephrased the question a little bit. $\endgroup$ – Robin Kramer Oct 4 '16 at 10:20
  • $\begingroup$ It's still quite hard to answer the question after your edits. The thing is, you want to have a trigger. That trigger can be either a physical trigger signal that triggers the initiation of the recording of all setups, or it can be a voltage signal that is recorded by all of the systems such that it shows up in your data afterwards. Alternatively, you can funnel all the recordings into one file and add a trigger signal and time stamps into that. Using a physiological response as a trigger signal used across different subjects sounds as a perfect gateway to disaster. $\endgroup$ – AliceD♦ Oct 4 '16 at 10:21
  • $\begingroup$ If you have a bag of money - I can recommend Biopac or other companies - they deliver modular physiological recording setups that are triggerable and customizable according to your demands $\endgroup$ – AliceD♦ Oct 4 '16 at 10:25
  • $\begingroup$ Sadly I do not. We will be using the Empatica E4 (HRV and GSR), Movisens EdaMove (GSR), and Suunto Memory Belt (HRV). These all tend to be more usable for in-the-field studies (when used individually) and, most importantly, cheaper. The stopwatch tactic also works, but is just not reliable enough and is very error-prone. Having such a marker/trigger would thus be fantastic. $\endgroup$ – Robin Kramer Oct 4 '16 at 10:43

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