The brain does nothing to naturally suggest the idea that it is the cause of human thinking, human learning or human recall. When you recall something, your body does nothing to suggest that you are using your brain to retrieve the memory. If I retrieve an apple on my table, my body gives me two different signals that my hand is being used to retrieve the apple. The first is the sight of my hand grasping the apple, and the second is the feeling of the apple in my hand. But if I retrieve a memory of my childhood, my body does absolutely nothing to hint to me that my brain is being used to perform this retrieval. The memory could be stored locally in my soul, or non-locally in some mysterious external consciousness infrastructure unknown to us.
Even when we scan brains with medical devices such as MRI machines, when a person recalls something there is no convincing evidence that information is being loaded from a brain location. A typical MRI scan of someone retrieving a memory will show something like a half of 1% variation from region to region in the brain, something that tells us basically nothing.
When you run very fast, your body does something to tell you that your heart helped to enable such fast running. You can feel your pulse and see that your heart is beating faster than normal. But when you engage in demanding mental activity, the brain does nothing at all to suggest to you that it is the source of such mental activity. You are not able to detect any sign of a brain working harder, such as pulsations coming from your head. If you attempt to read your pulse by touching your head after demanding mental activity, you will not feel such a pulse.
If you connect a human to an EEG device that reads brain waves, the readings from such a device will not show any greater brain activity during demanding mental activity. If you do an fMRI scan of a brain while someone is doing demanding mental activity, the scan will show no evidence that brains are working faster when you think harder. What such a scan mainly shows is blood flow. There is no increase in blood flow when people think harder.
So what can someone do if he is a believer in the "brains make minds" dogma, and he wants to make it seem like brains are worker harder when you are doing more difficult work? Lacking any real evidence to support such an idea, what a person may do is just make things up, shoveling baloney and BS. That is what went on in a recent article in Psychology Today.
The article by T. Alexander Puutio had the misleading title "Great Thinking Is Supposed to Make Your Brain Hurt" followed by the doubly misleading bunk title "Thinking hard hurts, and that’s exactly how you get smarter." No, thinking hard does not hurt, and thinking hard does not make you smarter. Exercising physically (such as running every day) actually improves the ability of the body to perform at a task such as running. But there is no evidence that thinking hard improves your intelligence.
Puutio makes this claim:
"Those who’ve tried may have found that good thinking—the insightful, heavy-lifting kind—is not just hard. It can bring about sensations startlingly close to physical fatigue, even pain."
You may feel your body feel a little tired after spending hours working on a problem, but it is not at all true that you feel any sensation at all from your brain after such activity. Brains do not at all hurt after heavy thinking.
Puutio makes these unfounded claims, which are certainly not established by a low-quality scientific paper he cites:
"In effect, sustained mental effort generates a kind of 'metabolic residue,' not unlike the lactic acid that accumulates in overworked muscles. The brain, sensing this, sends fatigue signals to encourage you to stop before damage sets in."
The scientific paper he cites provides no robust evidence for any such claim. The paper's claims that there were slightly higher levels of glutamate in the brains of subjects who engaged in more strenuous mental tasks. The study was one of those fishing-expedition affairs in which there is no pre-registered hypothesis to be tested, and checks may be made for dozens or hundreds of different things, looking for some difference. The sample size was too small for a robust result study of this type -- only about 20 subjects. Anyone checking in dozens or hundreds of places in two small sets of about 20 subjects will always be able to find some little difference somewhere. The technique used (something called diffusion-weighted H-MRS) is not a reliable technique for measuring the chemical contents of brains. It's a technique depending on spectroscopic analysis, in which all kind of weak, hard-to-interpret noisy signals are received.
In experiments like this, spectroscopic analysis is like being in a noisy high school cafeteria trying to pick up what someone on a distant cafeteria table is is saying. To give another analogy for what it is like trying to analyze spectroscopic data coming from the brain, consider the visual below:
This text consists of many different sentences, overlaid on top of each other. Imagine trying to extract a particular word from such a mess. That's pretty much impossible. It's a similar deal for a neuroscientist analyzing spectroscopic data from a brain, because what such a person gets is signals from many different chemicals, arriving all at once. Unless you are very lucky, there is almost no way to reliably extract which part is a signal from which chemical, compound or element. But with a mess like a scientist gets in such a situation (or a mess like the one shown above), there are unlimited opportunities to see what you are fervently hoping to see. All that can be truthfully said about such a mess is something like this: "The data is too noisy for me to say much of anything reliable about it."
Providing no evidence that heavy mental activity causes brains to hurt, Puutio gives us this lame BS claim: "In a sense, good thinking should make your brain hurt." Later he makes this baloney claim: "When your brain tells you it’s tired, it’s not being lazy. It’s protecting itself." Brains don't tell you they are tired, and no one has ever hurt their brain by thinking too much.
The main idea in the article of Puutio is that your brain hurts when you think too hard. That is a fictional notion contrary to human experience. People don't experience head pain or brain pain from thinking too long or too hard. Someone may sometimes get a headache when doing heavy cognitive work, but there is no evidence that headaches occur more commonly during heavy cognitive activity.
Below is Figure 3 from the paper "Perceived triggers of primary headache disorders: A meta-analysis." We see a report on what previous studies listed as triggers for a headache, largely based on the reports of those who had headaches. We have no mention of cognitive activity as a headache trigger.
Over the past 12 years I have spent endless hours working on the posts of my blogs, many of which involved topics requiring the most subtle reasoning. Not once did such activity ever cause me to feel the slightest bit of head pain. In my life I have noticed only one possible headache trigger: that extreme disruptions in sleep schedules can cause a headache.
The term "I'm tired" or "I'm tired of" means quite a few different things in English. A person may say that his arm is tired, and may mean he has an aching sensation in his arm. Or when a person says he is tired of something, he may merely mean he is looking for some change in his activity. For example, a person may say, "I'm tired of reading this book," or "I'm tired of playing this game," meaning he wishes to engage in some different activity, without actually feeling physically tired. Asked to work on some hard math problems, you may say, "I'm tired of doing this." But there is no actual ache of weariness in your body or your brain. Brains do not have muscle tissue, and cannot get tired.
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