From the article: Facebook’s promise to advertisers is that its system is smart, effective, and easy to use. You upload your ads, fill out a few details, and Facebook’s algorithm does its magic, wading through millions of people to find the perfect audience.

The inner workings of that algorithm are opaque, even to people who work at Meta, Facebook’s parent company. But outside research sometimes offers a glimpse. A new study published Tuesday in the Association for Computer Machinery’s Digital Library journal finds that Facebook uses image recognition software to classify the race, gender, and age of the people pictured in advertisements, and that determination plays a huge role in who sees the ads. Researchers found that more ads with young women get shown to men over 55; that women see more ads with children; and that Black people see more ads with Black people in them.