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The essential guide to the algorithms that run your life

From shaping what we read and buy to diagnosing illness, algorithms play a key role in every aspect of our lives. Here’s what you need to know about the most important ones

By Leah Crane, Clare Wilson, Chelsea Whyte, Donna Lu, Daniel Cossins, Timothy Revell, Matthew Sparkes, Anna Demming and Alexander McNamara

16 June 2021

New Scientist. Science news and long reads from expert journalists, covering developments in science, technology, health and the environment on the website and the magazine.

Bratislav Milenkovic

IT IS almost impossible to go a day without interacting with an algorithm. They help direct the whole of our online experience, recommending what we should buy, read, watch and listen to. Some 74 per cent of adults in the US use Facebook at least once a day – and what they see is decided entirely by an algorithm. Offline, they are increasingly used to help us make tricky decisions, screening job applications, moderating exam results and even directing which crimes police investigators focus on.

As they have become ubiquitous, algorithms have generated a mixture of hype and concern. On the one hand, we are regularly told that they can be opaque and biased. On the other, we hear that they can be incredibly handy, pulling off tasks that humans can struggle with, from optimising complex trade logistics to spotting the earliest signs of disease in medical scans.

So what’s the truth about algorithms? It helps to understand that the word can mean quite different things (see “What is an algorithm?“). It also helps to get to know some of the algorithms that shape our lives – so that’s what we’ll do over the next few pages.

1 SOCIAL MEDIA

Facebook’s news feed

Few algorithms wield as much power as those under the bonnet of Facebook. The social media giant’s algorithms control which updates its 2.8 billion monthly users see from which friends and what headlines they read on their news feed.

When we speak of the “Facebook algorithm”, we’e actually referring to dozens of pieces of software that are based on a range of technologies and are constantly being tweaked. This software analyses…

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