This article from Nautilus on common myths about the brain is important enough that it’s worth it to summarize the three myths for those hesitant to read the whole thing. I also add a fourth.
Myth 1: The brain is compartmentalized
“Myth number one is that specific parts of the human brain have specific psychological jobs. According to this myth, the brain is like a collection of puzzle pieces, each with a dedicated mental function. One puzzle piece is for vision, another is for memory, a third is for emotions, and so on.
“…not that every neuron can do everything, but most neurons do more than one thing. For example, a brain region that’s intimately tied to the ability to see, called primary visual cortex, also carries information about hearing, touch, and movement… In addition, the primary visual cortex is not necessary for all aspects of vision.
“Perhaps the most famous example of puzzle-piece thinking is the ‘triune brain’: the idea that the human brain evolved in three layers. The deepest layer, known as the lizard brain and allegedly inherited from reptile ancestors, is said to house our instincts. [But] brains don’t evolve in layers, and all mammal brains (and most likely, all vertebrate brains as well) are built from a single manufacturing plan using the same kinds of neurons.”
[Note: It’s fine to use the “lizard brain” as a metaphor. I’ve done it. But just like when we talk about genes “wanting” things, we have to be careful we don’t start to think that’s actually how it works.]
Myth 2: The brain is a passive observer
“Myth number two is that your brain reacts to events in the world. Supposedly, you go through your day with parts of your brain in the off position. Then something happens around you, and those parts ‘light up’ with activity. Brains, however, don’t work by stimulus and response. All your neurons are firing at various rates all the time. What are they doing? Busily making predictions.
“You’re not a simple stimulus-response organism. The experiences you have today influence the actions that your brain automatically launches tomorrow.”
[Note: Other researchers would say that those neurons are constantly manufacturing a holistic sense of reality by means of an integrated, controlled hallucination.]
Myth 3: Dualism
“The third myth is that there’s a clear dividing line between diseases of the body, such as cardiovascular disease, and diseases of the mind, such as depression. The idea that body and mind are separate was popularized by the philosopher René Descartes in the 17th century (known as Cartesian dualism) and it’s still around today, including in the practice of medicine.
“Your brain creates your mind while it regulates the systems of your body. That means the regulation of your body is itself part of your mind.
“When it comes to illness, the boundary between physical and mental is porous. Depression is usually catalogued as a mental illness, but it’s as much a metabolic illness as cardiovascular disease, which itself has significant mood-related symptoms. These two diseases occur together so often that [it’s possible] one may cause the other.”
Myth 4: The brain is a computer
In every period of history, our image of the brain has changed to reflect the latest fad. In Descartes’ time, when science was divorcing the natural from the supernatural (which had previously existed together), it was dualism. During the industrial revolution, phrenology saw the brain as a physical mechanism made of functionally distinct interchangeable parts.
In the era of computers, the brain is supposed to be hardware to the mind’s software. Thanks in no small part to science fiction, people expect we will soon be able to transplant brains from one body to another, like swapping a hard drive, or even to transplant minds from one brain to another.
But the brain is not a computer. It’s an organ. Like the liver, it has many overlapping functions, one of which is to cause a mind. Your brain causes your mind.
That doesn’t mean your mind is immutable. People with certain brain lesions can develop different personalities, for example. But it’s almost certainly not possible to instantiate your spouse’s mind on your brain, or vice versa.
The brain is so wholly integrated into the body that I’m not sure we’ll ever transplant brains either, but I’m sure someone will try. I suspect it will be easier to develop a substrate that replicates a mind and to transplant that instead.
I also expect the brain is doing a lot more than we think or even expect. One of the early lessons of biology for me was that many of the behaviors we associate with intelligence do not require it. An organism can exhibit complex behaviors with the simplest of “programming.”
There’s a species of wasp, for example, that checks its hole for predators every time it comes home with a bee. It sets the corpse a specific distance from the opening and then goes inside. If the bee gets moved, the behavior is reset. The wasp will return it to the appropriate spot and go in to check again, on and on forever, illustrating the difference between intelligence and memory.
Indeed, the wasp will theoretically repeat this loop an infinite number of times, although the sadistic scientists who kept moving the bee only did it thousands of times (or something like that).
As the article notes, slime molds also exhibit complex behaviors, despite that they are basically a single giant cell. A wasp at least has a nervous system, however primitive. Slime molds are just multinucleated bags of protoplasm.
But they are, in a sense, “smarter” than the wasp. For example, they get around the memory problem by leaving chemical tags everywhere they go. If they encounter such a tag, they “know” they’ve already looked there for food and go somewhere else, avoiding the infinite loop.
They can even remember things without leaving a chemical trail. More than that, they can teach others. Slime molds that are cut will form two new organisms, but the reverse is also true. Slime molds next to each other will merge into a new organism, like The Thing. That new organism will “remember” what the other two had learned.
It matters because we are now commercializing robots that seem intelligent. They exhibit complex behaviors, including context-dependent responses, and yet, unlike slime molds, they are not even alive, let alone conscious.
Part of the way we achieve this effect with machines is simply by giving them a REALLY BIG memory. If you gave the slime mold the ability to create new chemical tags and to encode a binary response (attraction/aversion) to each, it would also learn behaviors that seem highly intelligent.
We know this because it already does this to some degree. As the article points out, slime molds don’t like strong light, but they do like good food sources, and they balance the attractive/aversion responses in novel ways. They also adapt to harsh environments and can share that adaptation. (Per the article, they can already approximate the complexity of the Tokyo rail system.)
Of course, as I keep pointing out, intelligence is not consciousness. It is also not memory, although people with big memories often seem intelligent.
A machine can be intelligent but not conscious. It can also be intelligent and have no memory, just as a person with a certain brain disorder can be alive and conscious but have no memory (and may or may not be very intelligent).