The seduction
A growing graph of linked notes *feels* like a growing mind. You can see it. It's beautiful. Every note you add makes the structure more impressive, and the act of deciding how to link a note genuinely does involve thinking.
But look at what you are actually doing for those hours: writing, organising, linking, tagging. Notice what is absent — you are never being tested. There is no point at which the system requires you to produce anything from memory, which means there is no point at which the thing that causes learning occurs.
The externalised memory problem
The explicit premise of a second brain is that you don't need to remember, because the system remembers for you. For a writer or a researcher, that's a reasonable trade. For a student, it's fatal — you sit the exam with your first brain only, and the second one is on a laptop in your bedroom.
And more deeply: you cannot think with facts you have to look up. Reasoning happens in working memory, and an insight requires two things you know to collide. They cannot collide if one of them is in a note.
Where it's genuinely worth it
- A dissertation or thesis. Real research over months, where connections between sources are the actual output. Here it earns its keep.
- A long-term reference you'll actually consult — methods, protocols, code snippets.
- Working out what you think, where writing is genuinely the thinking.
For learning a taught module and passing its exam? Retrieval practice and spacing, which are considerably less fun and considerably more effective.