Biological Basics: Reaction Time

   Reaction time is a critical factor in a combat situation. A tiny fraction of a second in who moves first, whether or not someone can react quickly enough to parry a blow, an instant of indecision, or a fractionally swifter strike can easily make the difference between life and death. Ways to improve that time are widely sought.

   So lets take a look at the various steps.

   The first item is sensory information – mostly visual and kinesthetic. It’s mildly hard to beat the natural systems here: the eyes are too close to the brain for much transmission delay, and – while the visual cortex does a fair amount of processing – it also does it through a series of very well-established rules. While there is some flexibility there, and some provision for rule-changes (1), the fact that this stage is essentially hardwired and relatively short means that there is relatively little room for improvement.

   Kinesthesia would normally have a minor timelag thanks to the transmission delay of information through the peripheral nervous system, up the spinal cord, and it’s basic processing through the hindbrain – but the system compensates by projecting the data. That’s why, if you unexpectedly stub your toe, there may be a momentary feeling of your leg being ahead of where it actually is: the projected data does not match the actual data (2). Information from the ears is normally less vital in combat than that from the eyes – but the discussion is otherwise almost identical. Touch is of relatively little importance – many people will not even register a wound until after combat is over – and is subject to many of the same conditions as kinesthesia anyway. Balance comes into play as well, but is primarily a function of kinesthesia and the middle ear – and the information from the middle ear requires very little analysis. There isn’t much of any contribution to the delays there.

   Now that the brain has some information, it has to make a decision as to what to do. This is where the biggest delays occur, including “freezing up” – the shocked inaction that occurs under stress when the brain cannot reach a conclusion. There are a couple of ways to speed things up here though. The biggest, and most classic, is practice: learn to stay focused on the fight, and a lot of other considerations – your car keys, what’s to eat, if you’re being cheated on, how much your elbow hurts – will be effectively blocked out. That’s a lot of neurons you don’t have to wait for a consensus from.

   Well-established neural patterns are the quickest to trigger and the fastest to act: that’s a big part of the point behind kata, drills, and target practice. If the brain has only a few, well-established, patterns of action to choose between, the process may never get bogged down in conscious considerations at all, and those actions will go off more quickly and smoothly into the bargain. That can occasionally lead to you doing things that you didn’t mean too, but that’s the tradeoff you get for well-honed combat reflexes.

   Now that a decision has been made, it has to be converted into action. The motor centers convert the demands of the conscious mind – or its trained reflexes – into a series of motor-control impulses. That’s another tolerably-fast process, since – once again – most of those neural patterns are well established. Still, there’s probably room for improvement there. Of course, this is also one of the oldest, most well-adapted, and vital parts of the brain. Meddling here is very risky.

   The spine – while responsible for a number of simple reflexes (most of them related to damage-avoidance, where speed is most critical) and hosting portions of the sympathetic and parasympathetic systems – primarily acts as the pathway for signals to and from the brain to the rest of the body. Since muscle-control signals must be sent in sequence, and proper control demands that at least the start of return feedback be received before the next sequence is initiated, transmission delays in the spinal cord are a notable part of reaction time.

   The peripheral nervous system carries signals from the spine to the muscles and vice versa, as well as regulating a wide variety of autonomic processes through the sympathetic and parasympathetic systems. In general, it’s preferable to avoid meddling too much with the nerves regulating digestion, heartbeat, pupil diameter, artery constriction, bronchial responses, and all the other processes that keep the body functioning. Excessive meddling here is usually contraindicated. It’s also fairly difficult: the peripheral nervous system is made up of a network of fibers distributed throughout the tissues of the body. Still, nerve transmission delays in the peripheral nervous system make up a significant component of reaction time – in many cases, as large a component as the spinal delay.

   Finally, we have muscle-response/inertial delays: muscle fibers can only contract with so much force, and so quickly. The energy output is limited, thus the force that can be exerted is limited – and every bit of bone and flesh has inertia to overcome. Enhancing the contraction speed will accelerate the response (and result in quicker exhaustion, although – in a fight with modern weapons – that’s not a major worry), but there are severe limits to this process: the faster you try to move the anchoring bones and the flesh around them, the more power is required – and the greater the stress on the muscle, ligaments, tendons, and attachment points involved. Still, a good training regimen may realize substantial gains in this area.

   Now, Shadowrun assumes that the characters are – at the least – competent in a fight, and have probably been in a fair number of them. It also defines “Intelligence” more or less as a measurement of how quickly an individual processes information, and “Quickness” as a composite measurement of motor reaction speed and fine control. Ergo, the “Reaction” attribute – equal to (Intelligence + Quickness)/2, rounded down. Neither reaction, nor Initiative (normally equal to Reaction + 1d6 unless other modifiers apply) translate readily into any actual measurement of time, and they don’t really need to, since it only really matters who goes first and how often – which is a fair statement both in the game and in reality.

   There are, of course, a fair number of ways to get an edge in combat – augmentations, spells, and treatments, that are described in a number of ways. Notably, the practice effect is not one of them. While I have no way of knowing why the original authors didn’t include it, I wouldn’t either – simply because implementing the down side of trained reflexes (limiting your options to the ones you’ve trained) is pretty much impossible to simulate when you’ve got a bunch of players sitting around a table talking about what their characters ought to do.

   So, what can be done – past basic cmobat training – to increase a character’s “Reaction” and “Initiative”?

   Not too much in reality, at least as yet. Fortunately, we’re talking about Shadowrun – a setting which has another fifty years worth of technological advancements, functioning neural interfaces, magic, the ability to augment the brain, advanced chemical supplements, and various forms of genetically-modified biotechnological systems. That opens up a lot of options, which I’ll be going over in the next post on this topic.

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3 Responses

  1. […] Since cyberware for reflex enhancement has been covered pretty extensively this week ( Biological Basics: Reaction Time, Shadowrun Penumbra: Reflex Enhancement, Shadowrun Penumbra: Enhanced Reflexes III), I now have a […]

  2. sir / madam
    can give the reference or any other emprical finding of above artical. I am a student of psychology and i am working in the area of vigilance where reaction time use as a most common measure.

    • Hm. I almost forgot about this comment, but here is the belated answer:

      Unfortunately for research projects, this particular article is discussing the elements of a game setting. Now, I do like to keep things realistic, and I expect the players to be well informed. Thus this article is firmly based on the general mechanics of the brain and a variety of experiments, but most of the conclusions are simply based on logic and the application of some basic principles of neurology and computation. I did, however, forget the two footnotes I’d meant to add, so here they are.

      (1) Is based on experiments involving volunteers who wore goggles that inverted what they saw. After a few days, their brains compensated, again inverting the image. When they took the goggles off, this persisted briefly and then reverted. If they tried again, it took far less time to adapt. A related experiment on visual processing involved raising kittens in an environment that lacked vertical lines. As adults, they failed to perceive such lines in their environments and apparently could not learn to do so, demonstrating that the proper neural pre-processing circuitry had not developed.

      (2) Is based on experiments and calculations involving baseball; given nerve-conduction speeds, it is necessary to project the motion of the ball, start the swing, and to continue sending signals based on projected motions – of both the ball and the body of the batter – in advance of neural feedback.

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