Market

It sounds like harmless fun, letting users “buy” food, clothes or other products with no real-world cost, since most of these apps are free. But even when an app or website costs you nothing, they help advertisers better target you in real life.

For nearly a century, a strange band of 5,200 holes carved into a hillside has defied explanation. Stretching for nearly a mile along the edge of the Pisco Valley, Monte Serpe – "serpent mountain" – may have finally revealed its secrets to scientists.

Researchers found that when groups of people watch the same health promotion videos, their brain activity syncs up, indicating that the message has gone beyond being seen and heard. This approach could lead to more effective health campaigns.