My job, like many of yours, demands more from my brain than it is biologically capable of.

For all its complexity, the human brain is frustratingly slow, running at about 10 bits per second — less bandwidth than a 1960s dial-up modem. That’s not enough to keep up with the constant firehose of information we’re exposed to every day. “Raw-dogging” cognition while competing in today’s economy is like bodybuilding without steroids: a noble pursuit, but not a way to win.

Inside this story:

• The philosophical argument that phones, the internet, and AI tools are extensions of our minds
• Why humans love to outsource thinking
• How relying on devices changes our brains
• What happens when technological tools both enhance and undermine our ability to think for ourselves

Humans have never relied on sheer brainpower alone, of course. We are tool-using creatures with a long history of offloading mental labor. Cave paintings, for example, allowed our prehistoric relatives to share and preserve stories that would otherwise be trapped in their heads. But paleolithic humans didn’t carry tiny, all-knowing supercomputers in their loincloths.

Using tools — from hand-written texts to sophisticated navigation apps — allows humans to punch above our biological weight. Even basic applications like spellcheck and autofill help me write better and faster than my monastic ancestors could only dream of.

Today’s generative AI models were trained on a volume of text at least five times greater than the sum of all books that existed on Earth 500 years ago. A recent paper by researchers at Microsoft and Carnegie Mellon University found that higher dependence on AI tools at work was linked to reduced critical thinking skills. In their words, outsourcing thoughts to AI leaves people’s minds “atrophied and unprepared,” which can “result in the deterioration of cognitive faculties that ought to be preserved.”

The mind is so deeply attached to the self that it can be unsettling to consider how much thinking we don’t do ourselves. Reports like this may trigger a sense of human defensiveness, a fear that the human brain — you, really — is becoming obsolete. It makes me want to practice mental math, read a book, and throw my phone into the ocean.

But the question isn’t whether we should avoid outsourcing cognition altogether — we can’t, nor should we. Rather, we need to decide what cognitive skills are too precious to give up.

The extended mind, explained

In 1998, philosophers Andy Clark and David Chalmers published their theory of the extended mind, positing that the mind extends beyond the “boundaries of skin and skull,” such that the biological brain couples with the technology, spaces, and people it interacts with. Following this logic, by outsourcing my cognitive faculties to my phone, it becomes part of my mind.

I call my friends without knowing their phone numbers, write articles without memorizing source texts, and set calendar reminders to juggle more tasks than I could remember myself. The intimate coupling between my brain and my devices is both self-evident and extremely normal.

In fact, Clark and Chalmers point out that the brain develops with the assumption that we will use tools and interact with our surroundings. Written language is a prime example. Reading isn’t hard-coded into our genome, like the capacity for speech is, and until recently, only a small minority of humans were literate. But as children learn to read and write, neural pathways that process visual information from the eyes reorganize themselves, creating a specialized visual word form area — which responds to written words more than other images — about an inch above the left ear. The process physically reshapes the brain.

And as the tools we use evolve, for better or for worse, the mind appears to follow. Over the last 40 years, the percentage of 13-year-olds who reported reading for fun almost every day dropped from 35 percent to 14 percent. At the same time, they are doing worse on tests measuring critical thinking skills and the ability to recognize reliable sources. Some cognitive neuroscience research even suggests that shifting from deep reading to shallower forms of media consumption, like short-form videos, can disrupt the development of reading-related brain circuits. While evidence is still limited, several studies have found that short-form video consumption negatively impacts attention, an effect sometimes called “TikTok Brain.”

Ned Block, Chalmers’ colleague at New York University, says that the extended mind thesis was false when it was introduced in the ’90s, but has since become true. For the brain to be truly coupled with an outside resource, the authors argue, the device needs to be as reliably accessible as the brain itself. To critics, the examples Clark and Chalmers came up with at the time (e.g., a Filofax filled with notes and reminders) felt like a bit of a stretch.

But today, my phone is the first thing I touch when I wake up, and the last thing I touch before going to bed. It’s rarely out of arm’s reach, whether I’m at work, a bar, or the beach. A year after the first iPhone was released, a study coined the term “nomophobia,” short for “no-mobile-phone-phobia”: the powerful feeling of anxiety one gets when they’re separated from their devices.

In their paper, Clark and Chalmers introduced a thought experiment: Imagine two people, Inga and Otto, both traveling to the same familiar place. While Inga relies on her memory, Otto — who has Alzheimer’s disease — consults his notebook, which he........

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