Physical Intelligence:The Science of How the Body and the Mind Guide Each Other Through Life

Date Reviewed
April 24th 2023

“Physical Intelligence:The Science of How the Body and the Mind Guide Each Other Through Life” by Scott Grafton, a neuroscientist; for me, brings attention to another idea of “intelligence”. One that I hadn't considered.

Most people may view human intelligence as exercised abstract cogitation. This varies from almost none to somewhat more depending on person and circumstances. But the brain is “running things”, most fairly complicated, at an unconscious level 24-7.

When I saw the title it occurred to me the book might be about the kind of team-sport athletes who excel significantly beyond what their pure athletic aptitudes might suggest. I was thinking of Wayne Gretzky in hockey and Larry Bird in basketball.

But I was immediately disabused of that idea....or so I thought. The 'physical' idea in “physical intelligence” refers to action or anticipated action. And the intelligence is how well the brain learns the patterns for actions and recognizes situations for action.

However, in the first chapter, 'The Space We Create' on page 20 here comes 100 words or so about Gretzky. The chapter is about knowing what is around you, “situational awareness”. Originally it may have been primarily to be alert for predators. And danger is still a factor, but not for so many so much of the time.

But for Gretzky in hockey, with many players larger and heavier, there was a constant potential for danger. So, explains Grafton, over years of practice, Gretzky learned to keep track of where other players, teammates and opponents, were all of the time. But not only was he protecting himself, but he was seeing advantages as they developed and how they could be exploited. The need increases for star players under more constant attention.

Through the book, Grafton has a technique of using an ongoing story that both illustrates physical intelligence and draws people in before giving them the heavier technical material. It is like a teacher going off topic with an anecdote before continuing with the work portion of the class.

The author is a serious lifelong hiker, not just the kind that trudges along hiking trails, but one who challenges rugged terrain off the trails. He uses the first two or three pages of each chapter to advance the story of one particular mountain hike before tieing it into the relevant aspect of physical intelligence. Hand-on or feet-on activities like hiking, driving a vehicle and climbing a ladder are all examples and they are improved with practice and experience. And the activities require the co-ordination of several areas of the brain. And learning and direct physical experience are needed to develop it and it leads to a sense of control and knowing one's limits.

Physical intelligence also includes using and even imagining and designing 'tools' for a situation from the materials at hand. This kind of intelligence is almost always operating at some level where you may not be “thinking of anything”. This may relate to the connection between physical activity and brain health.

The author regards adventures in wilderness, representative of the primordial development and, as such, a refined example of challenge to physical intelligence. It offers obscurity with no lifelines. Solitude, with no social connections with increased risk and stakes, is another requirement that alters the nature of the trip along with roughness and little trace of human influence. He or she is relying as exclusively on oneself as possible. As nearly as possible, the circumstances would be those of human evolution, involving lots of wandering where behaviour has to adapt to changing circumstances.

Physical intelligence is regarded as a lower form below that related to verbal and introspection. The physical is more hidden and not subject to much conscious introspection, says Grafton. The “higher” forms of intelligence are freed up for mulling because the physical takes care of the other needs.

Surprisingly, below the internal verbal chatter most of the mind is dealing with the “physicality of being alive”. How important it is may become more apparent when aging persons are used to driving then loses their licences as their faculties decline. It has been a way they have been “projecting themselves” into the world.

In one chapter, he never seems to get into the science and the wilderness story continues. The chapter is basically all the ways to foil bear attempts to get your food when camping. It is a pleasant and informative respite from heavy reading.

The material in this book is complicated and seems more dense with no subheads in the ten 20-30-page chapters.

Not infrequently paragraphs will take more than a page. And only occasionally are there gaps in the text.

Readability would be made easier with subheads to remind the reader of the subject of the moment and allow stopping points other than chapter end.

A minor, but persistent thing I noticed was that the author uses the female gender for all anonymous references. Maybe it is his way of countering the opposite which has gone on for generations.



Vigilance, he says, is “at the heart of any animal's physical intelligence to stay ahead of danger, to predict and to respond.” It becomes automatic combining vision, touch and positions of the joints.

Strokes, impairing parts of the brain, can underline how important physical intelligence is.

A sense and awareness of space around one is more developed in human brains than those of other primates and we have a wider sense of space within the environment as such we have a “larger operational theatre”. And this is one place where artificial intelligence is seriously lagging human ability. And sense of space can vary from visual with light to sound when no light.

Experience allows one to filter out the relevant from the irrelevant in the circumstances and note changes and anomalies. He cites examples of issues and dangers that can loom in the wild environment he is traversing.

Contrasting with what is normally categorized as intelligence ”as a species we did not evolve to meditate or to be mindful. These are recent cultural inventions.”

In physical activity, people may get “tired” more quickly when less physical intelligence is demanded, such as walking on a uniform surface.

The brain is constantly looking for “affordances”, opportunities learned through direct physical experience, to respond to in activity and they vary with what appears and the capability of the actor. It is a bonding of perception and action and knowing what is possible. These judgements are also an impediment for AI.

As their faculties decline, old people become more vulnerable to falls. At the same time, they shy away from situations that could lead to falls and hence, with more loss of skill, become more vulnerable. Reducing this may be cataract surgery, balance and strength training. While still falling, the question is have they adjusted expectations to declining abilities. Regularly walking in complex terrains, he says, keeps people mindful of their skills as well as practicing them. This is not just a function of gym fitness.

The brain needs to keep track of the entire body all at once. People are quite aware of their size and shape so can often accurately estimate what they can and can't reach. The knowledge is based on the body schema, which allows movement, is developed by experience through life.

“It is the sixth sense that ultimately allows us to move quickly, naturally, and without thought.” Much of this is learned, if not unconsciously, at least as normal course. More complex movements may have required concerted effort.

Too much of the same movement can cause dysfunction (focal dystonia), which can be ameliorated by varying activities.

And in conclusion “riding a bull requires as much body awareness and dynamic strength as any sport out there.” If training “body awareness” was a goal then yoga is part of the solution.

Feedback control is the sensing and responding such that the performance of any action can be improved.

The second great problem of movement is how to make a speedy correction and it is called “efference copy” or “hidden hand” and it seems faster than thought itself, says the author. All athletes, he says, are on it in order to catch or hit a moving target, and that is learned. This originates in the parietal lobe of the brain.

Many of our wiring diagrams go back evolutionarily to the beginning of locomotion in vertebrates, he says, and despite being hidden by new controllers, they remain.

To give some perspective, about 350,000 axons (“wires” that carry information”) go into the arm. All but 35,000 are to feel position, touch, temperature and pain. Only 35,000 axons are carrying motor signals and most go into the shoulder and forearm and a surprisingly small 1,700 provide all the dexterity in the hand. Learning new skills has come from the brain through the spinal cord. The number of neurons passing from the spinal cord to the muscles depends most on the size of the muscles.

Over thousands of years of evolution the number of grips and movements has distilled from infinity to a relatively small number, reducing the challenge for the brain. Movement of certain kinds may originate in several areas in the brain.

If the synergies or skills that have developed over years are not regularly used, as in aging, they decline. This change can lead to falls ( you don't “catch” yourself walking) as well as declining facilities.

Along with synergies are individuation, the refined control of individual muscles providing dexterity. And this dexterity, greater than other species, probably since the beginning of hominids, has been evolving and improving since then. Even now entirely new actions are created with novel combinations in the motor cortex. And also movements can be modified to transfer from one skill to another as neuron firing patterns are changed.

On following directions in journeys “grid people give instructions by drawing a map and landmark people will describe a series of turns.” A loss in reduced grid map way of thinking in middle age may be a harbinger of mild cognitive impairment.

A mental grid map with many details takes cognitive effort and is a practiced skill. GPS or texted phone instructions will not necessarily do the job.

The human brain can generalize and move on to a different, but related, problem and work on a solution where artificial intelligence, without the flexibility, must start over.

The author points out that sequential problem solving requiring contiguous actions is much more difficult than single actions. This is pointed out in the chapter showing how bears have learned to defeat food containers, not just jumping on a Volkswagen to pop the trunk.

Trial and error over many attempts can lead to a solution that once learned can be used with minimum mental effort. This experience, in many situations, is one of the reasons that seniors may be good at problem solving.

Problem solving isn't just reliant on intelligence, but also motivation.

His chapter entitled “Purpose” discusses tools; what they are, how variously they can be envisioned and what species uses them. It seems that many, if not most species of animals, including earthworms use tools, depending on how wide you define “tools”. A stick is one of the most readily used and recognized tools. In humans, tools start to be seen to a degree by the human body as a part of it. However, distinguishing between self and the tool can expand the ways a tool can be used. A stick may be used to reach and extract something and as such become an extension of arm or finger. But it could also become a spear which is thrown some distance from the body, illustrating the difference between the tool and the body. A tool essentially focuses, increases and extends energy.

He uses the term “causal properties of movement”, an idea employed in using tools. “Being able to lift a rock with one hand requires an enormous amount of visual and motor coordination.” Grasping an object is both mundane and complex. And preceding it is perception (size, weight, shape) and experience to decide what can be picked up.

“From scans, it is clear that brain areas which represent ideas about actions and tools are in places different from those for faces, cars, houses, environments, and so on. Actions and the use of tools constitute their own special category of knowledge.”

“We usually don't think of walking as an act requiring much in the way of intelligence. But, in fact, walking more than any other action a person does, demonstrates a beautiful calculus that the brain endlessly performs to inform movement with grace, stability, and, above all, efficiency.”

For the average sized person it takes 55 calories to walk a mile. The brain figures out the most efficient way to walk in different conditions. And the brain continues to modify and fine tune optimal stride length and cadence for optimal efficiency. It is constantly learning and trying to find efficiencies as it is presented with different circumstances such as carrying a rucksack, bag of groceries or heavy coat.

Much of this is done in the cerebellum of the brain. “The cerebellum learns and remembers things about action that are fundamentally different from what the rest of the brain remembers.” It is responsible for maintaining finesse of movement with aging.

Walking is most efficient when slow and it declines with speed.

Muscle fatigue may be triggered by the brain to protect the body from injury, proactively before muscle fatigue can occur. Music can reduce the sense of fatigue and one often finds music playing in gyms. A slow moving clock may also trick the brain. “Fatigue” is now determined to be an “emotion”.

The brain may limit exertion early in an activity in order to have energy at the end. This scenario may be over cautious.

To optimize performance requires practice. “Physical intelligence learns how much fatigue to ignore.”

The idea that perseverance is a result of a personality trait “grit” (or some other heroic explanation) is giving way to experience, need for problem solutions and chemistry in the brain, altering chemistry in the body. Highly trained and experienced athletes can manage the pain of fatigue longer. It is often punctuated by the collapse over the finish line in an endurance sport.

Positivity, over pessimism, can determine how one responds to challenges against fatigue.

Some can collapse from fatigue without actually feeling fatigued. Head down may be the brain's response to impending fatigue by helping circulation to the brain, which is busy tuning cardiological and other responses to the increasing stress.

Brain interconnectedness of all functions is hardwired into all people. “Insofar as physical intelligence is concerned, the distinctions between mind and body are illusory.”

After the trek, that plays out through this book, he declares he is “healthier and stronger, both cognitively and physically”.

“For me the divide between the physical and the cognitive, as well as the emphasis on training rather than engagement, describes a condition of modern society that saddens me, as it does not allow for the holistic recognition of the unity of a person's feelings, thinking and physicality.”

“Intense physical experience, particularly in complex natural settings, places a demand on the brain to learn and to be proactive, even as it refines action to allow for best performance.”

“There is growing evidence that engagement tasks (physical adventures or learning experiences) are just as powerful, if not more powerful, than any other training strategy for improving the aging mind.”

Near the top of activities available to most is walking outdoors on challenging contours and on a challenging surface.

“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” to provide a sense of integrated well-being.