The debate on whether or not the brain is a computer is "just a semantic disagreement."

The debate on whether or not the brain is a computer is "just a semantic disagreement."

1/ A new paper on the “brain-computer metaphor debate” by myself and Tim Lillicrap is now out in Frontiers in Computer Science:https://t.co/yeNvgv43B6

tl;dr: The debate is useless because it’s actually just a semantic disagreement.

— Blake Richards (@tyrell_turing) February 8, 2022

2/ The perspective in this paper shows how my thoughts on the matter have evolved, in large part because of the conversations that I have had on Twitter. Though we all tire of these debates, it helped me to get clear on the matter at least!

3/ What I learned from all these discussions is that the definition of “computer” that I operate with (and which I argue is the predominant use of the word in computer science) is not the same as the definition most brain scientists use.

4/ Here, Tim and I make that explicit. We argue that, based on their use of the word “computer”, most computer scientists seem to define a computer as “a physical mechanism that can theoretically calculate any computable function”.

5/ That’s why they talk about computers made of quantum bits, analog signals, cells, DNA, gears, etc. The only thing that unites these disparate physical systems is their theoretical ability to calculate any computable function.

6/ If one accepts this definition then brains are *literally* computers, because brains are physical mechanisms that in theory can handle any computable function (ignoring time/memory/space constraints - which also apply to laptops, DNA, etc.).

7/ But not everyone uses this definition, including many brain scientists (and a few computer scientists too). I encountered this often on Twitter, where it became clear that most people I was “debating” with weren’t using the same definition as me.

8/ Indeed, what I now see is that many people (possibly the majority outside of computer science) use the word “computer” to mean “a discrete device that sequentially processes inputs step-by-step to generate outputs”.

9/ If one accepts this second definition, then brains are clearly not computers, and arguably, computers only serve as a weak metaphor for a small slice of what human brains can do.

10/ Thus, the “debate” is really just a semantic disagreement. Brains are either literally computers or definitely not computers, depending on your definition, and the most heated discussions seem to stem from misaligned definitions.

11/ When I first engaged with these debates on Twitter I took what I now realize was an overly prescriptive stance, basically telling others that if they weren’t using the definition I was using then they were wrong.

12/ But, that’s not how science works. We can’t force definitions on each other, though we can and should avoid useless semantic debates. So, it’s important for everyone to be clear about which definition they’re operating with.

13/ I’m happy Tim and I wrote this article, because I think it’s good for the field to get clear that this is a semantic debate, and not a useful one.

14/ On that note, I want this to mark my own departure from this debate. Zany face

I will use this as an opportunity to disengage from these arguments, and when they raise their head, simply clarify the definitions I operate with.

15/ In the end, if you accept the definition Tim and I use, you would agree, brains are literally computers. If you don’t use that definition, then fine, brains aren’t computers and they are likely a poor metaphor.

16/ To summarize: Let’s just get on with the science and leave these debates of little utility to the side. That’s ultimately the message Tim and I provide here.

Fin