Prevalence-induced concept change in human judgment.

https://science.sciencemag.org/content/360/6396/1465

I became aware of this last week while listening to Bret Weinstein’s Dark Horse podcast.
The gist is, through a series of experiments, people respond to decreases in the prevalence of some thing by expanding their ideas about it. Participants were shown a series of pictures with many different colored dots, and asked to spot the blue dots. In subsequent pictures, there were less and less blue dots, until finally there were none. But at that point the participants would begin to see the purple dots as blue dots. This same phenomenon occurred when show threatening faces; as the threatening faces diminished, they would see neutral faces as threatening. Finally, when unethical requests became rare, even innocuous requests were seen as unethical. This phenomenon is called prevalence-induced concept change, and it may explain why certain social problems can seem intractable- even as instances of specific problems diminish, people expand their concept of the problem.

Weinstein felt the study showed there was a built-in neurological relativism at work. The reasons this would develop are easy enough to grasp. If you look for berries in bushes, the biggest, most obvious ones are what you see and pick first. But as the berries are picked clean, your sensitivity to the stimulus heightens so that you can continue to find the food source. At some point though, as the berries are gone, you will find yourself grabbing at dark spots far in the bush because you thought you saw a berry where there were none.

At this point in the example, the physical feedback built in to the system tells you before long- there aren’t any more berries here, either look elsewhere, or find another food source. 
But if the phenomenon were, for a current political example, a socially constructed attitude- I believe that guy is a racist/sexist/whatever because I read his actions as such, then there is NO physical feedback that can act as a defeater. In such a scenario, the feedback is what the person ‘feels’ about another person’s motives.

This seems to have some explanatory scope in understanding the insistence that certain societal problems are no less prevalent now than 60 years ago, when they obviously are. As instances have reduced, there is a shift in concept that expands to let the viewer see it.