Right in the abstract it explains the use of the placebo in the randomized double-blind placebo-controlled trial. You can get around the paywall by using scihub. If you don't like this study you can find dozens on Google Scholar, and so long as it's pre-2021 you can use scihub to get around the paywall.

If you don't want to zap, that's fine. But don't make big declarations about zaps you'll give for information you haven't even bothered looking at. There's plenty of studies available for both sides of this argument and if you don't know that it's because you haven't looked.