The standard claim in bystander effect research is that an individual bystander's probability of intervening goes down as the number of bystanders increases (see, e.g., Wikipedia). Whereas this study looked at the probability of any intervention from the group of bystanders, which is a different thing.
The abstract of the paper actually begins with this distinction:
Half a century of research on bystander behavior concludes that individuals are less likely to intervene during an emergency when in the presence of others than when alone. By contrast, little is known regarding the aggregated likelihood that at least someone present at an emergency will do something to help.
So: not a debunking. And another example of why it's good practice to check the paper in question (or at least its abstract) and the Wikipedia article(s) on the topic rather than believing news headlines.
It also seems worth noting that this study looked at whether people intervened in aggressive public conflicts, which is a type of situation where the bystander's safety could be at risk and there can be safety in numbers. A lone bystander intervening in a fight is at higher risk of getting hurt, compared to a group of 10 bystanders acting together. This factor doesn't exist (or is much weaker) in situations like "does anyone stop to see if the person lying on the ground needs medical help" or "does anyone notify the authorities about the smoke which might indicate a fire emergency." So I'd be cautious about generalizing to those sorts of situations.
There may be a mild "Schrödinger's bystander" effect casting doubt on this new research as well. Nowadays people believe that their heroic actions are likely to be recorded, by cell phone or security camera, so that they will get their deserved recognition afterwards.
Can someone check this link out and see whether the methodology is actually sound?
One-line summary is that Surveillance Cameras Debunk the Bystander Effect H/T Hacker News.
More broadly I'm interested in anyone's sense of whether the bystander effect replicates, and whether the corresponding concept is misleading (and I should use something else instead).