The brain takes in and processes information fast. Well, pretty fast. But like everything else in life, ‘fast’ is relative. By the time you are finished reading this, you will be able to do an easy experiment that will show you how your brain struggles to process information that arrives too fast.
The speed with which the brain needs to process incoming sensory information, and make decisions about what to do with that information, has to match the timescales that impact the consequences of those decisions.
For example, if a baseball is coming at your head, your brain needs to interpret that an object is on a crash course, and be able to send motor commands to your muscles to coordinate a response that will move you out of the path of the ball fast enough so that it does not hit you. On the other hand, mountains will continue to increase in height and are actively moving if the geological forces that push them up are active. Yet we cannot perceive that. But frankly, who cares. It is of no consequence to climbing the mountain today, or next week, or in ten years.
In reality, your brain’s ability to react fast and make split second decisions is a combination of learned responses and actual decision making. Professional baseball players need to decide if the ball coming at them at 90 plus miles an hour is a hittable ball in a few tens of milliseconds. But the more they have to think about it, the poorer they do. Rather, learned experience is a key factor in picking up on small cues that allow decisions to be made faster, because you can act (or react) by anticipating a known outcome based on experienced past events. As Yogi Berra once put it, “How can a guy hit and think at the same time?”.
An issue of much broader significance are driver reaction times behind the wheel of a car. Car accidents where human error is the only cause accounted for 57% of all accidents in one study. Human error compounded by other factors accounted for over 90% of accidents. The measured reaction times of drivers across driving tasks that incorporated different expected and unexpected distractions ranges from 0.7 to 1.5 seconds. Here, again, learned experiences come into play when mitigating the bombardment of incoming cues the brain has to deal with to make potentially life or death decisions in very short periods of time. These neurobiological considerations are also critical to traffic engineers tasked with designing and building roads and other transportation infrastructure.
Tic Toc: Why Does the Brain Take so Long?
When your brain makes a decision, a number of things need to happen. First, sensory information needs to be taken in, which involves the need to transduce (i.e. change) and encode energy from the environment into neurochemical and electrical signals that the brain can interpret.
For example, in the case of vision, the energy is electromagnetic radiation, in other words, light. The photoreceptor neurons in the retinas of your eyes are responsible for the process of phototransduction, which takes incoming light and converts it into a neural signal. For hearing, compression waves made up of air molecules mechanically vibrating back and forth due to energy delivered from the object or process that created the sound undergo a process of mechanical to neural signal transduction in your middle and inner ears.
This sensory information then needs to travel to your brain to be processed. Often, there is the integration of multiple sensory modalities in the deeper parts of the brain before it reaches the cortex. The cortex is where higher cognitive processing and active thinking take place. Different parts of the cortex specialize in processing different kinds of sensory information. For example, visual information goes from your retinas to a part of the brain called the lateral geniculate nucleus before it goes to primary visual cortex. Through a series of processing stages in successive parts of the visual cortex, much which neuroscientists still do not fully understand, sensory visual information is then transformed into an internal mental model, in other words, an internal picture, of what the outside world looks like.
Your perception of the visual world, how you experience and feel what you see, is the result of the internal model your brain builds from the raw visual information it has access to. This is why different people ‘see’ or perceive different things even if they are looking at the same object. Think about optical illusions, or an image hidden in a work of art, for example. All of this has to happen before the brain acts on that information. That takes even more time. It could involve pulling up past experiences or memories the brain has been exposed to in the past in order to influence a decision. Or it could require computing different scenarios that calculate the probability of possible events in order to assess risk.
The bottom line: Your brain is not as fast as you think when you have to, well, think. It takes time for all these processes to take place.
Reflexes React. No Thinking Required.
In contrast, reflexes are faster. Perceptively faster. When you accidentally touch a hot stove, the reason you pull your hand away immediately without thinking about what you just did is precisely because the action does not require any thinking at all, literally. The signals that command your hand and arm to pull away never go to the brain. It is a short one hop (single synapse) connection loop between the neuron doing the sensing, through your spinal cord, to the motor neurons that control your muscles. The sensation of pain however, does require signals to go to your brain to be processed and interpreted, which is why you experience the perception of pain caused by the hot stove a fraction of a second after you have already pulled your hand away.
The Vestibular Ocular Reflex
Another reflex, meaning again that there is no active thinking or decision making involved, is a visual reflex called the vestibular ocular reflex (VOR). You will be taking advantage of the VOR to do an experiment in a minute that will prove to yourself how slow your brain can be. The VOR is a more complicated reflex, but a reflex nonetheless. The VOR acts to stabilize images on your retinas while you move your head around. It is what allows you to fixate on a point and maintain your fixation even though your head might be moving. Try it out. Pick a letter in this article and hold your gaze on it. You can move your head in any direction — up or down or side to side — while keeping your fixation locked on your chosen letter. That is the VOR in action. It generates compensatory eye movements equal in magnitude but in the opposite directional angle of your head movement, thereby allowing you to maintain fixation.
Instead of being a spinal cord reflex though, the VOR involves a three neuron loop in the brainstem — the evolutionarily older part of the brain that integrates incoming information and sends it to the cortex. But it does not involve processing neural information in the cortex. In other words, there is no thinking involved.
Try This at Home …
The VOR can be used to directly experience how visual information that requires processing by the visual cortex takes physically quite a long time. How long? Long enough that the rate at which the information is arriving is faster than your brain can processes, in essence overwhelming it.
Here’s how: Take one of your arms and extend it straight out in front of your face, palm up, and your fingers slightly curled so that with your palm flat your fingers are pointing up. Keep your arm extended in front of you with your fingers at eye level. Keeping your arm and head still. Shake your hand back and forth vigorously. You will notice that if you shake your hand fast enough, your fingers will look blurred.
Now stop and reset. Start the same way again with your arm extended, palm up and fingers curled up in front of your face. But this time, keep your arm and hand completely still and shake your head back and forth at roughly the same frequency that you were originally shaking your hand. This time, you’ll notice that your fingers do not look blurry. Why? Because when you shake your hand while you keeping your head still the visual information of your hand moving has to go through all the visual pathways to the cortex, where it is processed and interpreted. And this takes time. In fact, it takes so long that your brain cannot keep up. And so your hand looks blurry.
But when you keep your hand still and shake your head, as far as your cortex is concerned nothing is moving at all. The visual information is static. Your VOR compensates for your head movements by moving your eyes in an equal but opposite direction, which being a reflex, is much faster.
So the next time you go to catch that baseball, don’t think too much.