> So, kids are tattle tales?

No, tattle tales report rule breaking to third-party authorities. This is about direct intervention with the rule-breaker.

> Did we need a study to tell us this?

If we want to quantify and see how it varies across, say, the urban/rural divide (as this does with challenging), then, yes, certainly, but it's not this study.

In my experience kids are tattle tales when they have had their power to intervene directly significantly curtailed. I remember a kid asking me to tell my daughter to stop doing some behavior (she was a few years younger than him). I asked him if he had already asked her to stop and he looked at me like I was from mars.

At least where I live, many kids have been taught in many ways that direct intervention is something that will get them in trouble, and tattle-tales are at least partly a result of that.

This is also IMO why girls are more likely to tattle-tale. Girls, on average, get in way more trouble for instigating physical violence than boys, so they have had one method of direct intervention more strongly curtailed.

Eventually we would see a [citation needed] below the claim.