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20200628 – Physical Intelligence



The main idea of this book per author is this: ” A rich and complex connection to the physical world demanding abilities that blur distinctions among mind, brain, and body; proactive decision-making regarding physiological events and action execution; physically challenging do-it-yourself projects in complicated situations that require ingenuity, strength, and a willingness to stray off the beaten path: these desiderata, in their variety and complexity of physical action, allow for the sustenance of enviable personhood. The challenge for our future, particularly as we more and more partake of a cocooned urban lifestyle, will be to find settings analogous to nature that will require sufficient complexity of physical intelligence and ensure the physical experiences we need to sustain our health and provide us with a sense of integrated well-being.”


Here author defines the notion of “physical intelligence”: the components of the mind that allow anyone to engage with and change the world. Inside the brain there is no single module or bit of tissue that makes this possible. Instead, the action-prone mind draws on a multiplicity of capabilities”. He links it to his experience as hiker, stating that it becomes evident only when one is within natural environment – wilderness. Then author points out that human evolution occurred in wilderness, rather than at home or in the office, and it is demonstrated by our physical intelligence. Finally, author discusses iceman Ötzi and how the physical intelligence kept him alive in very challenging environment.

1: The Space We Create
Author starts this chapter with describing beginning of his hiking trip into mountains and then moves to discuss how mind creates concept of space and orient body within this space:” The brain routinely combines vision, touch, and positions of the joints to make a volume around the body. There is good evidence that some neurons code for particular parts of space, such as the space within reach. Other kinds of neurons are active when an object or the hand approaches a particular spot on the face, like one cheek or the other”. The author describes several neuropathological conditions that illustrate what happens when parts of these multiple systems within the brain go out of commission or out of balance. After that author presents result of several relevant experiments using fMRI and other methods of direct scanning of the brain. He also discusses high performance sportsmen and their superior situational awareness, which allow some impressive physical feats.  

2: Surfaces
Here author movers to discuss surfaces. He starts with physical challenge of working in mountains, pointing out that it requires concentration of attention in the process of just walking to such extent that it consumes more than 80% of brain activity at the moment. He then discusses brain areas heavily involved in this process and what happens when these areas are damaged. The next topic is discussion of formation of this functionality in human brain starting with infants learning to move. The complexity of movement, especially walking, well demonstrated by inability to implement this functionality in robots. The final part of this discussion is about ground-level falls that quite surprisingly is a big problem and not only for elderly.

3: Shaping the Self
This chapter is about mental representation of body shape and ways to adjust it to environmental space in such way as it is required to achieve some objective. It is also reviewed in relation to some areas of body, which were damaged. It is not limited to the brain, but also includes “different sensory organs within the joints, ligaments, tendons, and muscles that provide information about body position had been identified through the microscope. The computations these sensors enable are complex.”  Author discusses how it all works, experiments and observations of situations when various parts of the system are broken, and then returns back to the story of his hiking for illustration.

4: The Hidden Hand
In this chapter author moves to feedback control. He starts with analysis of use of spear that requires precise control of hand movement. He compares it with process of missile control. Then author discusses what happens when due to brain damage feedback signal stop coming and person even loses notion of possession of hand for example. The details of this process author describe as “hidden hand”: representation of body and surrounding environment within the brain as internal copy of movement-producing signal (efference).

5: Pulling Strings
Here author uses the story about difficulties of repairing a stove in the field because this action required specific positioning of his hands that he initially could not do. It brings discussion to motor controlling system and here is how author describes results of research:” nearly every one of these command neurons with the strongest influence over the muscles drives only one muscle. Each cortical motor neuron will influence only one muscle. This is good news in that it simplifies the wiring diagram. It also provides enormous freedom for the motor cortex to create any sort of movement it wants (provided the bones and joints will allow it!) and to individuate, to isolate the contractions of particular muscles in new ways.” Author then points out that each cortical neuron could participate in many kinds of actions and discusses in details how it all happens.

6: Perspectives
In this chapter author moves to the problem of orientation: how people know where they are and which way to go. He starts with experiments that show that without some direction processing people tend to walk in circles. He then discusses how animal and people find way, usually by utilizing some direction clues that go into developing mental representation of the map. Then author looks at it from another angle: mapping a brain using fixed box on the head to create referential frame.    

7: Learning to Solve Problems
This is very interesting and even funny chapter about problem solving. It retells the story of struggle between bears and tourists supported by park service. The latter trying to prevent bears getting to the food by using boxes, hiding food in cars and so on, while bears often succeed in getting to this food. Then author discusses how it is done: “hierarchical reinforcement learning and model-based learning work well when there are just a few actions to plan as a sequence. But what of problems whose solution requires many steps? As steps are added, the number of potential solutions grows exponentially. Here is the curse of dimensionality in problem-solving in all its glory.”

8: Purpose
In this chapter author moves to use of tools. He points out that it used to be common believe that use of tools differentiates humans from other animals, but with better knowledge and research it is obviously not correct. The interesting part of discussion is mental mechanism that turns tools into part of a body by including it in the body schema. There is also a quite interesting discussion of related neuronal activity. Moreover, tools and actions are united in the mind and author discusses how it was discovered by observing individuals with damaged brains.

9: Costs
This chapter starts with author’s health emergency in the middle of nowhere in mountains when getting to other people become question of life and death. Author describes how he was walking all day overcoming various difficulties and exhaustion. In process author discuss in detail how process of walking is the best and most effective exercise for which human body was naturally evolved. The final and most important part of the chapter is discussion of tradeoff between cost and reward. In this case cost was loss of energy and stress on author body that author had to overcome to achieve his objective. Here is how it was achieved:” The calculus underlying all my trade-offs of speed, stability, efficiency, and grace was performed without my giving it a single thought. All I had to do was sustain the tempo”.

10: Of One Mind

The last chapter starts with discussion of fatigue. Author discusses various explanations of this phenomenon and note that continuing training allows conditioning of the body to diminish and somewhat control it. His example – top level athletes capable to control their body to such extent that they time energy complete expenditure exactly to the moment of achieving finish line. This demonstrates integrity of a person and author discusses how specifically it works by using quick stress responses:” There are two lines of evidence that will eventually need to be reconciled. The standard view, based on extensive studies of patients who have suffered strokes and brain imaging of healthy people, is that the regulation of the heart is mediated through the insula: a hidden island of cortex located underneath the temporal lobe. In healthy subjects, changes in heart rate can be correlated with insula brain activity measured by functional MRI scans. And in patients with stroke, damage here can lead to catastrophic heart failure, presumably because of brief overstimulation of the heart. Recent anatomic studies by my colleague Peter Strick suggest that the insula serves as a control center to the parasympathetic nerves. These are the nerves that actually brake the heart and allow us to rest and digest. There is also good evidence that this area senses feelings from the viscera of the body. It is monitoring heart rate, respiration, and activity of the gut, making sense of what is going on. Damaging this sensing might also eliminate feedback control and lead to runaway stimulation of the heart.

The alternative model, which we know less about, maintains that the cingulate cortex and other areas of the frontal lobe are key for connecting the mind to the body by proactively controlling fast-acting stress responses via the sympathetic nerves. This is the system that drives the heart harder and enhances blood flow to the muscles. The evidence supporting this conclusion is quickly mounting. In recent studies of patients with epilepsy, when electrodes are placed in the deep portion of the anterior cingulate and a jamming signal is introduced, there is an obvious and dramatic decline in systolic blood pressure that is sustained until the stimulator is turned off. Such fast changes could be sparked only by nerves, not circulating hormones. No other area of the human brain has ever been shown to manipulate blood pressure this reliably.”

At the end author strongly affirms his believe:” that the integrity of a person can be revealed through the intelligence of physical action. Intense physical experience, particularly in complex natural settings, places demands on the brain to learn and to be proactive, even as it refines action to allow for best performance.”


I also believe that human mind and body is one integrated entity, so any approach that concentrates only on one part of this entity is necessarily very limited and could not possibly inform effective actions of any consequence beyond direct and simple impact. Among multitude of data, research, and experiments I was very impressed with one case: person with multiple personality of which one personality was healthy and another diabetic. How switch in mind of this person from one personality to another impacted level of sugar in blood is very difficult to say, but demonstrative power of body/mind integrity of this case is unquestionable. I think that in very near future application of AI technology that would allow analysis of millions of parameters of a person simultaneously with status evaluation and valid prediction of result of any externally directed action would allow removal of the very notion of being sick or even unwell if not completely, then close to it.

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