Here are specific sentences that make the claim:

> It’s one of the most enduring urban myths of all: If you get in trouble, don’t count on anyone nearby to help. Research dating back to the late 1960s documents how the great majority of people who witness crimes or violent behavior refuse to intervene. Psychologists dubbed this non-response as the “bystander effect”

The author said the bystander effect was "this non-response" which he describes in the previous sentence as "if you get in trouble don't count on anyone nearby to help." This is the very first sentence in the article.

> A new study published this year in the American Psychologist finds that this well-established bystander effect may largely be a myth. [...] The study finds that in nine out of 10 incidents, at least one bystander intervened, with an average of 3.8 interveners.

The author claims that the bystander effect is disproved if, in a group of people, "at least one" person intervenes.

> Instead of more bystanders creating an immobilizing “bystander effect,” the study actually found the more bystanders there were, the more likely it was that at least someone would intervene to help.

The author again claims that the bystander effect is disproved if "at least one" person helps.

But does it really debunk that effect?

The article essentially claims that the more people there are the more likely it is that _someone_ will intervene. Which isn't the same as no one feeling less inclined to help since there are other people around.

The whole point of the "bystander effect" is that this diffusion of responsibility leads to nobody intervening. Nobody cares if the chances of a specific bystander intervening goes down when there's a crowd, all that matters is whether someone intervenes, and the bystander effect claimed that a crowd meant the chances of intervention would go down overall.

I'm understanding that's not the finding, although that's the popularly understood point. You would expect each person to be individually less likely to help when there are other people around. Somebody else might have already intervened, and you might just be getting in the way. Not everybody can help, at least not at once. I mean, in some situations, people actually fear to intervene, and have a legitimate fear for their own safety, but if they can call the police once they're secure (or if they are clearly secure e.g. viewing from a distance), people do it. A lot of people called about Kitty Genovese as it was happening, watching it from their apartments. That became a newspaper article - which was basically typical right-wing linkbait: it wasn't slow police response, it was the heartless crowd that killed Kitty.

That Slate dot com tier take became a theory, developed experiments, and discovered something that was obviously mathematically true: if not everybody in a group helps someone that they see in distress (only a subset do), but individuals always help when alone, then in groups, the average time before response for each individual is going to go up, and the average likelihood of any response at all from a particular individual is going to go down.

This would be true even if people were always helped faster by groups rather than individuals, and a subset of every group always intervened. The types of people that bystander experiments found to be likely interveners could just adhere to the stereotypes that people think of as physically authoritative and look to when something occurs. People look to them to intervene (large, male, athletic, maybe ethnic or rough looking in criminal/street situations) maybe those people intervene because there no one for them to pass the responsibility off to.

I imagine psychologists care a great deal about that difference.