Feb 02 2017

What Is Normal?

normal-spider-flyOne of the main themes of this blog is metacognition – thinking about thinking. This is a critically important topic because much of our thinking is subconscious, or it is not explicit. This means we are not aware of exactly how our brains process information and come to certain conclusions or decisions. In fact, we may have false beliefs about how we arrive at our decisions.

Cognitive psychologists study how people think, and knowledge of this field can help us become more aware of the otherwise unrecognized assumptions or processes in our decision-making.

Take an apparently simple concept such as “normal.” What does it actually mean and how do we use this concept to think about the world? (“Normal” has a specific mathematical definition, as in “normal distribution,” but I am not talking about that here.) A dictionary definition might be, “conforming to a standard; usual, typical, or expected.” This doesn’t quite tell us how we decide what is “normal.”

In medicine use of the term “normal” has fallen out of favor, because it is imprecise, and also because it may contain a moral judgment. We still use it when referring to numbers, such as normal blood pressure, but even then it is not conceptually precise. Normal may be different for different people in different situations. When we are making an effort to be clear in our language we will use terms such as “healthy” or “physiological” (which is distinguished from pathological).

In psychiatry especially use of the term normal has fallen out of favor in an attempt to disentangle moral judgments from clinical judgments.

Recently cognition researchers Bear and Knobe published a paper called: Normality: Part Descriptive, Part Prescriptive. They also discuss their paper in this New York Times article. Essentially they found that what people consider to be normal is a combination of what they think is typical and what they think is ideal. They give a simple example of what they mean. People think that the average number of hours people watch tv per day is 4. They also think that the ideal numbers of hours to watch tv per day is 2.5. When asked what is the “normal” number of hours people watch tv, the average answer was 3 – part way between typical and ideal.

They found the same result for many different examples. They even made up a fake example:

We even made up a story about a fictitious type of tool — a “stagnar” — and provided information about what it was used for and what it typically looked like. Pretty soon, our participants had developed a conception of the normal stagnar that was intermediate between the average stagnar and the ideal stagnar.

This findings, if confirmed, has several implications. First, it is just good to know how our brains typically work. “Normal” is a combined judgment about what is actually happening and what “should” be happening. This confirms what was observed in health care, especially psychiatry, that there is a moral judgment in deciding what is normal.

This can also mean, however, that when something becomes common it also becomes somewhat normal. Social psychologists have observed this for a long time – different cultures have different concepts of what is “normal.” In some cultures it is more normal to, for example, cheat on your taxes, or inflate prices. The question is – is it normal because people do it, or do people do it because it is considered normal? The answer is probably both – behavior and judgment play off each other.

The authors give as an example the apparent recent trend of “fake news” or politicians boldly lying. The more this happens, the more it will seem normal, and therefore the more acceptable it will become.

I think an excellent example of the implications of understanding how we think about “normal” is homosexuality. In this case, however, ideology seems to influence how we balance typical and moral in the calculation of normal. There are those who think, on moral grounds, that homosexuality is abnormal. They are taking an extreme moral definition of normal.

On the other side are those who think that homosexuality is normal because it is common. About 3.4% of the population self-identify as other than straight. (I won’t get into the debate here about how accurate this number is.) Similar numbers are found in the animal kingdom. For those who feel that there is nothing morally wrong about homosexuality (and for the record, I count myself in this group), they emphasize that it is a common variant of human, and in fact animal, behavior.

What’s interesting here is how people can apparently shift their definition of “normal” to suit their ideological needs on a specific topic. They can do this easily because they are not explicitly aware of how we typically decide what is normal.

This example also shows how problematic the concept of normal is, because it is a blend of two factors that are disconnected. Something can be common but morally wrong, or rare but morally neutral. We tend to see rare behavior as “deviant” in some way. In fact, the word “deviant” is interesting because it implies deviation from what is typical or average, and also conveys a connotation of morally repugnant.

We really need to separate this things in our minds, which we can do with effort and discipline. That is metacognition – recognizing that, for whatever reason, we tend to blend two concepts into a messy amalgam, when in fact it is more precise and useful to keep them separate.

This is where language plays a huge role, because words reflect how we think, and many argue they constrain how we think. “Normal” is a messy and imprecise word, and if you use it your thinking is likely also messy and imprecise. In most situations it is probably best just to avoid the word, and to think about what you really mean.

15 responses so far

15 Responses to “What Is Normal?”

  1. daedalus2uon 02 Feb 2017 at 11:24 am

    I have spent a lot of time thinking about what is “normal” in the context of physiology.

    My conclusion is that there are no “normal outcomes”, and their can’t be any “normal outcomes” because “normal” can only be “normal as process”.

    There is no teleology, so outcomes can’t be “normal”, because “normal outcome” implies teleology.

    An example I like to use is the example of Brittany and Abigail Hensel.


    From my perspective, these MZ twins are the outcome of normal development. During the early proliferation and differentiation of the embryo they grew from, there was a certain level of adhesion between different cells. If there had been more adhesion, those cells would have grown into a single individual. If there had been less adhesion, those cells would have grown into two “normal” MZ twins. If the adhesion between cells was in the “normal range” (a range that produces otherwise normal outcomes”, what basis is there for calling this outcome not normal?

    If the processes going on inside cells are “normal”, then the outcome must also be “normal”. A better term to use is “typical”. Brittany and Abigail Hensel are not “typical”. They are “normal” but “atypical”.

    As an aside, as far as is know, these twins appear to be neurotypical. What that means is that neurodevelopment appeared to occur via typical pathways and achieve a typical result. The two individuals are different, demonstrating that development is chaotic (in a mathematical sense) where differential early differences accumulate into macroscopic differences; as in the Butterfly Effect.

    It is extremely likely that all systems regulated by development (that is essentially all physiological systems) also experience extreme sensitivity to initial conditions; a developmental Butterfly Effect.

    Differential fluctuations at the level of “noise” in levels of adhesion between cells can result in atypical phenotypes like this. Presumably there are other differences in “normal” phenotypes that are below the level that is considered atypical. Those differences are real, and are in the “normal” range.

    The human genome only has something like 3×10^9 bases. There isn’t enough information to specify differentiated cell phenotype and location for 10^11 brain cells and the 10^15 connections between them. The “information” that specifies those connections must come from somewhere. It pretty much has to come from noise-level fluctuations during development. That “noise” affects development and then gets “filtered” to remove non-functional cells and connections.

    You need a human genome to generate a human phenotype, but you also need the process of development, and that process of development determines what the adult phenotype is like, not the genome. Virtually all control of physiology is “local”. Individual cells regulate their own DNA expression, ATP production, cell cycle, proliferation, and so on. The only “signals” that cells can use to do that, are either internal, or signals on the cell surface.

    Development of tissue compartments like the brain have to be “bottom-up”. That is they are assembled by individual cells “doing their thing” and interacting or not with their neighbors. Neurodevelopment (in the early stages) can’t be “top-down”, because before neurodevelopment happens, there is no “top”. The brain develops from a state where it has zero cells. There is no brain to direct neurodevelopment while there are zero brain cells.

  2. Rogue Medicon 02 Feb 2017 at 11:38 am

    One of the things I try to explain to people describing an ECG (ElectroCardioGram) showing a regular, or slightly irregular, sinus rhythm is that the normal term normal sinus rhythm is misleading.

    The term normal suggests that there is nothing wrong with the rhythm, or with the heart, when it is not unusual for a patient to have a heart attack with a normal sinus rhythm being accurately displayed on the ECG.

    We are subconsciously telling ourselves, Nothing to see here. Move along.

    We are fooling ourselves and discouraging investigation of what may be causing problems by unnecessarily adding the term normal.

    In this setting, normal does not add any information, but suggests that we know more than we actually know.

    Why lie to ourselves?

    Because we trust ourselves and don’t bother to check our assumptions to see if they are valid.


  3. SteveAon 03 Feb 2017 at 4:22 am

    Rogue Medic: “One of the things I try to explain to people describing an ECG (ElectroCardioGram) showing a regular, or slightly irregular, sinus rhythm is that the normal term normal sinus rhythm is misleading.”

    Does this boil down to: normal is what’s usual, but what’s usual is not always good?

    Or is that too simplistic?

  4. MFDHon 03 Feb 2017 at 9:11 am

    This goes a way toward explaining why some people in my acquaintance are constantly using “normal” as a synonym for “good.”

    …Or as a synonym for “natural” which is also, in their usage, a synonym for “good.” Normal and natural things, like water, are good. Unfamiliar and weird things, like oxidane, are bad.

  5. Newcoasteron 03 Feb 2017 at 1:37 pm

    @Rogue Medic, SteveA

    Well, the “normal” in normal sinus rhythm (NSR) does just refer to the rhythm itself, the regularity of the electrical activity in the heart that stimulates muscular contraction, but nothing else. So that one aspect..the rythm…may be “normal”, but it is only a snapshot of one aspect of what else may be going on in the heart.

    There is also “sinus arrhythmia”, which can be a variant of “normal”

    One can have ST elevation (which is one of the criteria for giving someone a thrombolytic in acute myocardial infarction) but the rhythm itself may still be “normal”. However, the most common type of MI these days is actually the NSTEMI (non ST elevation myocardial infarction) where the ECG may be entirely normal (NSR), as RM pointed out.

  6. Pete Aon 03 Feb 2017 at 2:40 pm


    Each parameter (of anything) that has been sufficiently analysed to establish its mean value, its probability mass function, its standard deviation, its risk-benefit ratio, and its cost-benefit, has a value that can be initially categorized as being:
    “normal” — nothing to be unduly concerned about;
    “borderline” — requires monitoring for changes;
    “abnormal” — requires immediate investigation.

    The “abnormal” category must be properly sub-categorized into: below/hypo/sub normal, and above/hyper normal. E.g. the treatment required for hypothermia is very different from the treatment required for hyperthermia.

    In cases where multiple parameters are involved, the normality or abnormality of each of the parameters cannot be summed using intuition (cognitive heuristics plus cognitive biases plus experience) because the phase angle between the various parameters is not precisely ±90 degrees: the parameters are not orthogonal / statistically independent!

  7. hardnoseon 04 Feb 2017 at 4:49 pm

    Obviously, deviations from normal can be good or bad. If it’s good, we say things like “extraordinary,” “exceptional,” “unusual.” If it’s bad, we say things like “abnormal,” “weird,” “strange.”

    The word “normal,” like most words, has different meanings depending on the context. How these researchers could not know this seems highly abnormal — but since we know they are cognitive psychologists, it is really not that surprising.

  8. Rogue Medicon 05 Feb 2017 at 3:15 pm

    Steve A,

    Does this boil down to: normal is what’s usual, but what’s usual is not always good?

    Or is that too simplistic?

    I think it is more of a criticism of people leaping to the conclusion that something being normal without a good understanding of what normal means and very little understanding of what abnormal means.

    Newcoaster mentions sinus arrhythmia, which is actually healthy (normal) among young healthy people. The inspiration and expiration of air produces changes in the pressure in the chest. The changes in pressure stimulate the vagus nerve (and probably by other mechanisms) and causes the heart rate to increase and decrease with the changes in pressure. It is as we get older, and become less healthy, that this effect decreases.

    Rather than arrhythmia, some people claim that we should use the term dysrhythmia, because dysrhythmia means bad rhythm, while arrhythmia means no rhythm. Except that this insistence that we describe the healthiest heart rhythm as bad makes a mockery of their point. We can use arrhythmia (lack of a regular rhythm) to describe the irregularity of the rhythm, without applying the judgment of good or bad, which is determined by further assessment of the rhythm and the whole patient.

    As with other uses of normal, it appears to indicate a desire for an overly simplistic dichotomy.

    Is it good or bad?

    If it is good, then it would be wrong to interfere, since it is the best it can be.

    If it is the best it can be, how is it possible to have a heart attack while still having a normal sinus rhythm?

    If it is bad, then we need to do something to make the bad go away.

    The best rhythm is actually a bad rhythm. One of the ways used to measure the condition of the heart is to measure R to R variability. The apps you can use to measure stress on your phone are often using heart rate variability, with less variability (normal) indicating increased stress. This is far from a perfect measure.

    Medicine provides many examples of using normal to make moral judgments by people who don’t understand medicine. King Richard III was understood to be immoral because of his physical deformities. It was believed that the gods placed these signs there as warnings of the immoral essence of the person. Remember that the history of Richard III was written by the people who killed him, since he was the last King from the House of York to rule England.

    Con men (and women) take advantage of the way we assume the opposite – that physically attractive people are somehow more honest, more trustworthy, more moral than someone like John Merrick (The Elephant Man).

    This is just another example of the perfect being the enemy of the good and the need for critical judgment to be able to understand the gradations of good, bad, and that which is much more normal – a combination of good and bad.

    Medicine is full of examples of the impossibility of pure good, although it is difficult to consider pure bad, since the main reason to not use something is that there is something better available for any possible use of a bad medicine. And then we sometimes find that there actually is a good use for a bad medicine, such as thalidomide (which is now used to treat some cancers).

    I prefer to be at least two standard deviations from the mean in many things. Life is, not easier, but much more interesting that way.


  9. Rogue Medicon 05 Feb 2017 at 3:21 pm


    Obviously, deviations from normal can be good or bad. If it’s good, we say things like “extraordinary,” “exceptional,” “unusual.” If it’s bad, we say things like “abnormal,” “weird,” “strange.”

    The abnormal, strange, and weird are often the best.

    In business, do we want to sell something abnormal enough that people will seek out the brand name or do we want them to choose the insignificant (normal)?

    Leadership is deviance.

    Following is normal.


  10. SteveAon 06 Feb 2017 at 4:30 am

    RogueMedic/Pete A,

    Thanks for your responses.

    “Newcoaster mentions sinus arrhythmia, which is actually healthy (normal) among young healthy people.”

    Only last week my eldest daughter (a young teen) was taken to A&E complaining of mild dizziness and heart palpations.

    She was found to have an arrhythmia which we were told was not a concern, though they didn’t go into details as to why not.

  11. BillyJoe7on 06 Feb 2017 at 6:11 am


    They must have meant that the arrhythmia itself was not going to kill her. In other words, it was not of concern to them. They could safely send her home, confident that she was not going to die. On the other hand, it was obviously a concern to her because it made her feel dizzy. Conceivably this could cause her to fall and injure herself. In fact, there was probably a slight chance that she could fall from a height with grave consequences but that this risk was not worth worrying about because of its rarity.

    My daughter had an ectopic focus in her heart which produced every alternate heart beat. We discovered this when she put her finger on an attachment to her sister’s iphone that sounds out your heart beats. There were paired beats separated by a larger time interval. Yet she was completely unaware of it. She had her ectopic focus cauterised, restoring a “normal” sinus rhythm. She was then found to have a bradycardia of 50 beats per minute – just like her dad’s unfit resting pusle rate (now about 40 because he IS fit). She was also completely unaware of that.

    Decades ago when I was really fit running marathons, my pulse rate dropped to below 35 causing an ventricular escape rhythm. Every night when I went to bed, my heart dropped into this ventricular escape rhythm. It was a bit annoying, because I could feel it. I soon learnt to train just that little bit harder. I found that my pulse rate at night was always that little bit faster if I’d run a little bit faster that morning, just enough to prevent the palptitations associated with the escape rhythm.

    Yeah, so nomal is hard to define and we best avoid that word.

  12. BillyJoe7on 06 Feb 2017 at 6:15 am

    SteveA: “they didn’t go into details”

    Never let them get away with this. She’s your daughter and you deserve the details. At the very least they should have given you the name of the “abnormal” heart rhythm so you could read up about it yourself and satisfy yourself that it is okay.

  13. SteveAon 06 Feb 2017 at 7:09 am


    In fairness to the medical professionals concerned, I should have said ‘my wife didn’t go into details’ since it was she who took the sprog in. She was satisfied that everything was okay, and has fairly stringent standards…

  14. Rogue Medicon 06 Feb 2017 at 7:55 am

    Steve A,

    There are many different kinds of arrhythmia.

    Syncope (or near-syncope) can be one sign of an arrhythmia, but there are other causes/contributors to consider. Onset of menstruation can be very problematic to adapt to. Blood loss and hormone surges do not make it easy.

    I don’t know what the arrhythmia was, but you can ask for a referral to a pediatric cardiologist for a second opinion.


  15. BillyJoe7on 08 Feb 2017 at 5:37 am

    …or he could see his GP and have him name and explain the “abnormal” rhythm. And he could then improve his understanding by reading reliable references. If he was still concerned after that, maybe the cardiologist. He maybe could tell you no more than you could have found out yourself for free.

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