All of the above is true, but the actual effects are tiny. In the Facebook experiment, users were indeed more likely to post positive messages if they were shielded from negative news. But the difference amounted to less than one-tenth of one percentage point. Likewise, in the targeted adverts example, the makeup sold to introverts was more successful if it took into account the person’s character, but the difference it made was minuscule. A generic advert got 31 people in 1,000 to click on it. The targeted ad managed 35 in 1,000. Even that figure of 50 per cent improvement that I cited here,
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