Evolution and reaction speed

What is limiting the reaction time? Is it the length of neural paths, the efficiency of glial cells, the structure of the brain, or something else? Maybe all of the above? Let us check the animals we know and see what they can tell us. More cool facts here, here, here, and here.

Only elephants cannot jump

Of all mammals, I think only elephants do not jump. There is too much stress on their feet. A whale may pounce supported by the sea, but elephants do not want broken legs.

As young scientists, we were told a cruel and not very funny joke. “You teach flyes to fly, give the command and they fly. Then you cut their wings. Give the command, but they do not fly. Hence they do not hear the command. We conclude that flyes hear with their wings”.

A fair warning: it is easy to make stupid conclusions when discussing animals. I suggest taking every relevant finding with a healthy doze of skepticism.

Reflex vs reaction time

We can measure reflex time and we can measure reaction time. These are not the same. Occasionally we do not know what we measure. The reaction time usually assumes some conscious processing, and hence longer neural path and slower neural connections. Reflexes are usually unconscious. Most of the reflexes are processed in the cerebellum with an extremely fast myaline neuron connection to the body, at least in humans.

Myeline is an isolator that covers neural cells. It is secreted by glial cells. The signal may travel up to 100 (!) times faster if the neural connections are properly covered by myelin. Without myeline, the current along the axion is wasted in the surrounding tissues. Not all animals have myelinated neurons.

The evolution of myeline

In most animals, myeline is a double spiral covering the axion fibers. Most of the animals that have red hemoglobin blood also have myelinated neurons. It remains a fact that there are more myelinated invertebrates on this planet than myelinated vertebrates. However, some creatures have blue blood rich in hematocrit. Like the horseshoe crabs, whose blood is harvested for pharmacological use.

In fact, myeline is not the only factor in neural transmission. Mammals have axion fibers thoroughly myelinated but small in diameter, usually between 2 and 20 um. The fibers of giant squids are huge. Possibly between 200 and 800 um. A wider electrical wire will allow more current, but less voltage as the isolation is poor.

The better isolation and larger fiber allow faster reaction time. Penaeus and macrobrachium shrimps have red blood and a large fiber diameter. They are small creatures with very exceptionally fast reflexes. Their neural signals travel at around 200 meters per second. Our own signals will measure around 50 meters per second.

Size vs technique

Small animals will have faster reflexes. Their neural paths are shorter.

At the same time, the larger animals will have more massive body parts with huge inertia. So in general, the larger the animal the slower it will react.

We can measure the speed of the signal in axions directly. It is much harder to understand what is going on in the cerebellum.  Also, some reflexes happen directly in the spinal cord, and some reactions require high-level processing.

A competitive shooter gets a signal, draws his revolver, and shoots a target from three meters in less than 300msec for the entire sequence. It involves the processing of sensory signals, complex coordination, and sequence of operations.

Clearly a common flee detects a threat and reacts much faster, maybe x10 faster. And this is a complex reaction, not a reflex! Reflexes are significantly faster than that!

Speed, acceleration, and energy

While bigger animals are massive and do not accelerate that well, they can reach better velocities. Cheetah, swordfish, falcon, are not small. Large bones and large muscles provide excellent momentum.

Yet, to accelerate to greater speeds animals need a lot of energy. They heat up. Above certain size that stops being efficient. Land animals above 100kg weight slow down. They run out of energy and overheat before they can develop top speed. Cheetahs definitely overheat very fast.

Underwater speed

The limits are different in air and water, but they probably exist.

I quote:

When not at risk or hunting, dolphins travel at a leisurely speed of 10 kilometers per hour (kmh), which they can easily maintain for long distances. Orcas are slightly slower, traveling at only 6 or 7 kmh.  Bottlenose dolphins hunting speed have been recorded at 54 kmh, with orcas coming in slightly behind at 50 kmh. 

This is about as fast as a good submarine, but torpedoes travel faster. A submarine can travel around the world submerged. Swordfish the animal can travel at 100 kilometers per hour. Heavy swordfish torpedo can travel 54km at 130 km per hour. German press reports of an underwater super-cavitating anti-torpedo missile named Barracuda that allegedly reaches 400 km/h, but these cannot “fly” more than 7 km.

Who is the fastest land animal?

While a cheetah runs faster than any land animal, the sensomotoric delay of a shrew is very small. A shrew weighs several grams, and its reaction speed is around 10 msec. An average dog will weigh 10kg and have 80 msec reaction time. An elephant weighs several tons and will reach within 300 msec or more. At larger animals to offset slower neural conductivity, muscles will often generate force faster. For a large animal, it is easier to preserve speed and endurance is less important.

When we consider speed over large time periods, the equations change. Some muscles are very fast to release energy, but they will get tired very fast too. Others are not as explosively fast, but faster over long time periods.

Consider horses. In a short quarter-mile sprints quartes will probably win by a landslide. For a 3km race, thoroughbreds are nearly perfect. And for a 40km endurance race, Arabian horses are better. Each kind of horse has a slightly different physique to balance acceleration vs endurance.

What do we train when we train reaction time?

I do not really know what people train when they train reaction time. There are several factors.

Often the muscle mass of fast-twitch muscle increases. The calcium in the relevant bones also increases. The glial cells produce more myeline. The coordination is very fast and subconscious, e.g. in the cerebellum.  There is a faster secretion of adrenaline and a rise of the heartbeat. Probably there are additional reactions that I forgot to mention.

Another aspect is sensory. We learn to recognize patterns faster and react to them faster, possibly allocating dedicated neurons for that processing.

All of these aspects work together. When we speak about faster reflexes, we usually address neural conductivity. But when we discuss faster reaction, all factors contribute.

Perception time

When we train speedreading we do not really improve reaction time. We change the way we process patterns and analyze the stuff we read more visually. It is a sort of reprogramming the brain to use a different processor and then modifying the algorithm.

At the same time, training associative memory probably results in more myeline on associative fibers in the neocortex. Memory champions often have better connectivity between brain hemispheres and other small changes visible in fMRI. It is not clear if these variations contributed to success in memory sports, or the practice of memory changed the brain morphology.

Top chess players also have variations in their brain in the areas dealing with pattern recognition. Chess masters deal with certain positions as we deal with familiar faces.

When agents practice situational awareness they learn to recognize patterns most of us miss. I watch my son playing computer games. He snipes some point-size figure while I do not see any motion. After months of playing, he trained himself to recognize certain patterns and react appropriately.

Automated response

Clearly, all of the responses described here are automatic. A chess player balances into a better position, but from that position, most steps are almost intuitive. I think martial arts specialists act similarly. Their amazing speed comes from the well-trained automatic response.

If we need to weigh all pros and cons we tend to be indecisive. Our reaction time drops significantly. Most interestingly, our accuracy on average does not improve. Fast automatic responses quite often are the best responses. When we train AI, we usually do not train it to think, we train it to react to certain stimuli.

Ecological niches

Each kind of animal evolved for a certain ecological niche. Some animals are very agile and can react quickly. Other, different, animals are very fast and can maintain high maximal speed. Yet, totally different kinds of animals have great stamina and can keep high speed for long pursuit. There are those who are good at energy conservation or using special foods, and their metabolism is slow.

Each of us has his own niche in life. To be good in our niche we acquired certain adaptations. These adaptations are specific. Science, sports, arts, moneymaking, spirituality – these are very different areas of activity. Some skills may be transferred, but most skills are deeply specific.

Do not think about what you do not have, but be grateful for your competitive advantage.

Elephant shrew is FAST…

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