[GhostVII]

Once a metric becomes a target, it ceases to be a good metric. I think that people would find ways of targeting their learning towards these brain scans, without actually getting useful experience and learning, so their usefulness would go down. Similar to standardized tests I guess, that are probably a great measure of ability until teachers start targeting them.

[wjn0]

I think it's important to be careful with the vocabulary here (if only because of the site we're on).

There can be metrics that are targets which still remain good metrics. For example, in many machine learning competitions, the submissions optimize a known, given metric; but the test data is not known. Therefore, it is still a good metric.

I agree with the sentiment in this case, though.

[Someguywhatever]

I don't doubt that this would eventually be the case, people always learn to game the system eventually.