I recently attended a panel discussion titled Being Human in the Age of Intelligent Machines. At one point during the evening, a philosophy professor from Yale said that if a machine ever became conscious, then we would probably be morally obligated to not turn it off. The implication was that if something is conscious, even a machine, then it has moral rights, so turning it off is equivalent to murder. Wow! Imagine being sent to prison for unplugging a computer. Should we be concerned about this?
Most neuroscientists don’t talk much about consciousness. They assume that the brain can be understood like every other physical system, and consciousness, whatever it is, will be explained in the same way. Since there isn’t even an agreement on what the word consciousness means, it is best to not worry about it. Philosophers, on the other hand, love to talk (and write books) about consciousness. Some believe that consciousness is beyond physical description. That is, even if you had a full understanding of how the brain works, it would not explain consciousness. Philosopher David Chalmers famously claimed that consciousness is “the hard problem,” whereas understanding how the brain works is “the easy problem.” This phrase caught on, and now many people just assume that consciousness is an inherently unsolvable problem.
Personally, I see no reason to believe that consciousness is beyond explanation. I don’t want to get into debates with philosophers, nor do I want to try to define consciousness. However, the Thousand Brains Theory suggests physical explanations for several aspects of consciousness. For example, the way the brain learns models of the world is intimately tied to our sense of self and how we form beliefs.
Imagine if I could reset your brain to the exact state it was in when you woke up this morning. Before I reset you, you would get up and go about your day, doing the things you normally do. Perhaps on this day you washed your car. At dinnertime, I would reset your brain to the time you got up, undoing any changes—including any changes to the synapses—that occurred during the day. Therefore, all memories of what you did would be erased. After I reset your brain, you would believe that you just woke up. If I then told you that you had washed your car today, you would at first protest, claiming it wasn’t true.
Upon showing you a video of you washing your car, you might admit that it indeed looks like you had, but you could not have been conscious at the time. You might also claim that you shouldn’t be held responsible for anything you did during the day because you were not conscious when you did it. Of course, you were conscious when you washed your car. It is only after deleting your memories of the day that you would believe and claim you were not. This thought experiment shows that our sense of awareness, what many people would call being conscious, requires that we form moment-to-moment memories of our actions.
Consciousness also requires that we form moment-to-moment memories of our thoughts. Thinking is just a sequential activation of neurons in the brain. We can remember a sequence of thoughts just as we can remember the sequence of notes in a melody. If we didn’t remember our thoughts, we would be unaware of why we were doing anything. For example, we have all experienced going to a room in our house to do something but, upon entering the room, forgetting what we went there for. When this happens, we often ask ourselves, “where was I just before I got here and what was I thinking?” We try to recall the memory of our recent thoughts so we know why we are now standing in the kitchen. When our brains are working properly, the neurons form a continuous memory of both our thoughts and actions. Therefore, when we get to the kitchen, we can recall the thoughts we had earlier. We retrieve the recently stored memory of thinking about eating the last piece of cake in the refrigerator and we know why we went to the kitchen.
The active neurons in the brain at some moments represent our present experience, and at other moments represent a previous experience or a previous thought. It is this accessibility of the past—the ability to jump back in time and slide forward again to the present—that gives us our sense of presence and awareness. If we couldn’t replay our recent thoughts and experiences, then we would be unaware that we are alive.
Our moment-to-moment memories are not permanent. We typically forget them within hours or days. I remember what I had for breakfast today, but I will lose this memory in a day or two. It is common that our ability to form short-term memories declines with age. That is why we have more and more of the “why did I come here?” experiences as we get older.
These thought experiments prove that our awareness, our sense of presence—which is the central part of consciousness—is dependent on continuously forming memories of our recent thoughts and experiences and playing them back as we go about our day.
Now let’s say we create an intelligent machine. The machine learns a model of the world using the same principles as a brain. The internal states of the machine’s model of the world are equivalent to the states of neurons in the brain. If our machine remembers these states as they occur and can replay these memories, then would it be aware and conscious of its existence, in the same way that you and I are? I believe so.
If you believe that consciousness cannot be explained by scientific investigation and the known laws of physics, then you might argue that I have shown that storing and recalling the states of a brain is necessary, but I have not proven that it is sufficient. If you take this view, then the burden is on you to show why it is not sufficient. For me, the sense of awareness—the sense of presence, the feeling that I am an acting agent in the world—is the core of what it means to be conscious. It is easily explained by the activity of neurons, and I see no mystery in it.
Excerpted from A Thousand Brains: A New Theory of Intelligence by Jeff Hawkins. Copyright © 2021. Available from Basic Books, an imprint of Hachette Book Group.
Jeff Hawkins is the cofounder of Numenta, a neuroscience research company; founder of the Redwood Neuroscience Institute; and one of the founders of the field of handheld computing. He is a member of the National Academy of Engineering and author of On Intelligence.
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