This result doesn’t mean that the availability heuristic would be a myth, of course. It is, AFAIK, true that e.g. biased reporting in the media will throw off people’s conceptions of what events are the most likely. But one probably wouldn’t be too far from the truth if they said that in that case, the brain is still computing relative frequencies correctly, given the information at hand—it’s just that the media reporting is biased.
It doesn’t seem fair to say that humans are, given the information, arriving at justifiable conclusions, when humans are also the ones giving the information. “Humans believe the right things given the information,” doesn’t seem as persuasive when you attach “Humans skew information when passing it to make it seem more likely than it is.”
It doesn’t seem fair to say that humans are, given the information, arriving at justifiable conclusions, when humans are also the ones giving the information. “Humans believe the right things given the information,” doesn’t seem as persuasive when you attach “Humans skew information when passing it to make it seem more likely than it is.”