Appreciating that humans are two minds in one

Take this syllogism with a false premise:

  1. All monkeys climb trees
  2. The porcupine is a monkey
  3. The porcupine climbs trees

Now, does it?

If you are like most people where the part of your brain (corpus callosum) that allows communication between the left and right hemispheres is intact, you likely think that a porcupine does not climb trees, it runs on the ground and it’s prickly. You know that a porcupine is most certainly not a monkey. [Actually there are porcupines that climb trees but the experimenters and their subjects did not know this fact.]

But in experiments performed on subjects who had their left and right hemispheres separated and were then asked the same question, the answers reveal that the different hemispheres of our brains have their own way of approaching the question.

A subject who starts out with both hemispheres responds to the question as you likely did. A porcupine is not a monkey so it doesn’t climb trees. When, however, her right hemisphere is inactivated (so only her left hemisphere is processing the information) she replies, “the porcupine climbs trees since it is a monkey.”

But her answer to the follow-up question: “But is the porcupine a monkey?” is “no.” She knows it is not.

Finally the whole syllogism is presented again. This time, she responds that, yes, it is a monkey because that is what is written on the card.

When the right hemisphere of the same individual is presented with this same logic task, she replies, “How can it climb trees, it’s not a monkey, it’s wrong here!” If the experimenter then points out that because this is a logic problem, the conclusion must follow from the premises, therefore a porcupine climbs trees, she is indignant. “But the porcupine is not a monkey!”

This scenario has been repeated in multiple situations with varying syllogisms with false premises and the results are consistent. The intact individual gives a commonsense answer. “I agree it seems to suggest so, but I know in fact it’s wrong.” The right hemisphere sees through the false premise and thinks the conclusions are absurd. The left hemisphere sticks to its (false) guns. “This is what it says,” says the left brain.

Let’s pause to consider this discovery and its implications. It reveals something about our brains that is quite unintuitive. Each hemisphere literally thinks differently. Iain McGilchrist in The Master and His Emissary, explains that truth, for the left hemisphere, is inside the mind. Truth is coherence with what it already knows. In contrast, the right hemisphere prioritizes the outside world. Truth, for it, relies on correspondence with something other than itself and being true to something apart from ourselves.

In a sense we already have two minds. The left and right hemispheres of our brains serve different purposes, are concerned with different things, and operate in distinctly different ways, yet both are involved in everything. The left and right hemispheres are in opposition, our brains containing an essential asymmetry. Our brains are not just tools that help us make sense of the world, they are what brings the world into being.

Brains have to grapple with a broad conflict, namely differences in context between which world we are inhabiting at any moment. Are we in the world of me or the world of we? In the world of me, it’s just you and what you need. You are in competition with other individuals. You need your attention to be wilfully directed and narrowly focused. On the other hand, in the world of we, you need to account for yourself as part of a social group. You need to feel as though you are something bigger than yourself, perhaps even to exist “through” others. In this context, your attention needs to be wide open, diffuse, alert to whatever exists outside of your individual context, with attention to external allegiances.

The evolutionary pressure to do both of these things—control the individual whilst caring for group relations—sets brains up as asymmetrical entities. These two opposing perspectives on the world need to be neurologically separated in order to function. Attention has intention. The left hemisphere specializes in purpose. “It always has an end in view, and downgrades whatever has no instrumental purpose in sight,” writes McGilchrist. The right hemisphere has no specific plans or ideas. “It is vigilant for whatever is, without preconceptions, without a predefined purpose.”

The left hemisphere works within a closed system. It has the advantage of perfection but this comes at the expense of being mediated by the right hemisphere. Its knowledge is composed of its own models and representations. It cannot break out on its own. It sees grains of sand and builds them up to a heap in an analytical process.

The right hemisphere, by contrast, sees the heap of sand and stays wide open while it uses various strategies (including analytics and language provided by the left) to break it down into grains while relating it to the broader context (why sand, what’s it for, how can I move it?). It is the right hemisphere that knows how to deal with imperfect knowledge and how to keep things open. It is comfortable with ambiguity because it knows that is all there is.

While the left hemisphere gets stuck on determining when the heap is complete (how many grains make a heap?), the right hemisphere keeps track of the process of a growing heap. For the right brain, the heap comes into being, in a sudden shift of perception, it just is.

Evolution has dealt with asymmetries in the world by building brains that represent the same asymmetry. We have to be able to do two things at the same time. We have to focus on what we know and not be distracted by new information in order to be productive and maintain consistent performance, yet we can’t afford to be blind to what’s changing in the world. We appreciate accuracy and precision yet we reject it when it constrains our freedom to adapt. Let’s say that again: we reject accuracy when it interferes with our agency because agency is adaptive.  

Rather than define human achievement as “perfected utility through banding together to form groups,” he offers instead that great human achievement is to have learned through intersubjective experience and to ultimately “transcend utility altogether.” Humans have broken out of the blind choices of chance and pressures of natural selection, speeding up our evolution because we choose our own values, forms of thinking, and modes of behavior.

Great Human Strength: It is uniquely human to value agency as adaptive and to use our agency to work together based on a set of common values.

Great Human Weakness: If we over-value left-brained thinking, we risk overlooking the vitality that right-brained thinking brings to us.

Machine Opportunity: Designs that help us use our right brain. Designs that are right-brained.

Machine Threat: Designs that overuse one aspect of our (and an AI’s) cognition.