Metric, because if people didn't enjoy the experience, they wouldn't come back. but you mentioned frances haugen earlier, and one of the pieces of evidence she published was the study facebook did looking at instagram users in the uk and in the us, particularly teenage girls. it said between about, i think it was about 20% in the us, up to about 30% of the uk, girls in the research group, said that they had heightened levels of anxiety and depression having used the site. but the same research also said they felt they couldn't not use it because they couldn't miss out on what their friends wer...