How do we move through our world? How do skills work? (And therefore, how should we best learn or coach skills and movements?)
The movement of animals — like our hitting a tennis ball or a rattlesnake striking prey — is Gibsonian not Cartesian.
From the abstract to “Rattlesnake Strike Behavior: Kinematics” by Kenneth V. Kardong and Vincent L. Bels:
Four major results were obtained. (1) Neurosensory control of the strike is based primarily upon sensory inputs via the eyes and facial pits to launch the strike, and upon tactile stimuli after contact. Correction for errors in targeting occurs not by a change in strike trajectory, but by fang repositioning after the jaws have made contact with the prey. (2) The rattlesnake strike is based upon great versatility and variation in recruitment of body segments and body postures.
Success in movement comes in adapting variations in a skill to variations in a goal,;it does not come from following some Platonic “perfect form.“
An animal initiates a causal sequence toward some object in an ecological context, and varies its body positioning in the skill and in the world as it obtains perceptual input and feedback from the world. The process is like a Boydian OODA Loop.
Regarding averages and variation, and a Platonic view of things, it’s as the great evolutionary biologist Stephen J Golud said, in a different context, in his article “The Median is Not the Message:”
We still carry the historical baggage of a Platonic heritage that seeks sharp essences and definite boundaries. … This Platonic heritage, with its emphasis in clear distinctions and separated immutable entities, leads us to view statistical measures of central tendency wrongly, indeed opposite to the appropriate interpretation in our actual world of variation, shadings, and continua. In short, we view means and medians as the hard ‘realities,’ and the variation that permits their calculation as a set of transient and imperfect measurements of this hidden essence. If the median is the reality and variation around the median just a device for its calculation, the ‘I will probably be dead in eight months’ may pass as a reasonable interpretation.
But all evolutionary biologists know that variation itself is nature’s only irreducible essence. Variation is the hard reality, not a set of imperfect measures for a central tendency. Means and medians are the abstractions. Therefore, I looked at the mesothelioma statistics quite differently – and not only because I am an optimist who tends to see the doughnut instead of the hole, but primarily because I know that variation itself is the reality. I had to place myself amidst the variation.
Also relevant regarding learning, memory, experience, and acquiring, and using a skill;
“All men by nature desire to know – – this is indicated by the pleasure we take in our senses. This pleasure is independent of their utility: we delight in them for their own sake and particularly in the case of sight…. Sense represents the first stage. Next comes memory in the case of the animals which have it. In man memory leads up to experience; many memories of the same thing occurring come in the end to have the force of a single experience.” —Aristotle, first chapter of Book A of the Metaphysics, as quoted by Thomas Heath in his book Mathematics in Aristotle.
The whole abstract to “Rattlesnake Strike Behavior: Kinematics:”
The predatory behavior of rattlesnakes includes many distinctive preparatory phases leading to an extremely rapid strike, during which venom is injected. The rodent prey is then rapidly released, removing the snake’s head from retaliation by the prey. The quick action of the venom makes possible the recovery of the dispatched prey during the ensuing poststrike period. The strike is usually completed in less than 0.5 s, placing a premium on an accurate strike that produces no significant errors in fang placement that could result in poor envenomation and subsequent loss of the prey. To clarify the basis for effective strike performance, we examined the basic kinematics of the rapid strike using high-speed film analysis. We scored numerous strike variables. Four major results were obtained. (1) Neurosensory control of the strike is based primarily upon sensory inputs via the eyes and facial pits to launch the strike, and upon tactile stimuli after contact. Correction for errors in targeting occurs not by a change in strike trajectory, but by fang repositioning after the jaws have made contact with the prey. (2) The rattlesnake strike is based upon great versatility and variation in recruitment of body segments and body postures. (3) Forces generated during acceleration of the head are transferred to posterior body sections to decelerate the head before contact with the prey, thereby reducing impact forces upon the snake’s jaws. (4) Body acceleration is based on two patterns of body displacement, one in which acute sections of the body open like a gate, the other in which body segments flow around postural curves similar to movements seen during locomotion. There is one major implication of these results: recruitment of body segments, launch postures and kinematic features of the strike may be quite varied from strike to strike, but the overall predatory success of each strike by a rattlesnake is very consistent.
In “Rattlesnakes are extremely fast and variable when striking at kangaroo rats in nature: Three-dimensional high-speed kinematics at night” by Timothy E. Higham, Rulon W. Clark, Clint E. Collins, Malachi D. Whitford, and Grace A. Freymiller, they have a similar observation:
Predation plays a central role in the lives of most organisms. Predators must find and subdue prey to survive and reproduce, whereas prey must avoid predators to do the same. The resultant antagonistic coevolution often leads to extreme adaptations in both parties. Few examples capture the imagination like a rapid strike from a venomous snake. However, almost nothing is known about strike performance of viperid snakes under natural conditions. We obtained high-speed (500 fps) three-dimensional video in the field (at night using infrared lights) of Mohave rattlesnakes (Crotalus scutulatus) attempting to capture Merriam’s kangaroo rats (Dipodomys merriami). Strikes occurred from a range of distances (4.6 to 20.6 cm), and rattlesnake performance was highly variable. Missed capture attempts resulted from both rapid escape maneuvers and poor strike accuracy. Maximum velocity and acceleration of some rattlesnake strikes fell within the range of reported laboratory values, but some far exceeded most observations. Thus, quantifying rapid predator-prey interactions in the wild will propel our understanding of animal performance.
A few resources on JJ Gibson.
Dr. Rob Gray’s ( Associate Professor of Human Systems Engineering at Arizona State University) podcast episode “123 – The Legacy of James J Gibson I: Invariants & Direct Perception.”
Dr. Rob Gray’s ( Associate Professor of Human Systems Engineering at Arizona State University) podcast episode “124 – The Legacy of James J Gibson II: The Theory of Affordances & Its Application to Sports.”