The final point to make is obvious, but is often of critical importance in science. Unconscious assumptions or mindsets can, of course, be wrong, and can greatly impede progress. And by the way, another thing we know about the two brain hemispheres is that the hemisphere that specializes in finely-dissected, finely focused, analytic styles of perception, including detailed symbolic manipulation——usually the left hemisphere——is the hemisphere most prone to mindsets. That is the downside of its analytical power, its special ability to zoom in and grasp precise details. It is sometimes called the steel-trap mind. All this should further motivate us to cultivate taking more than one view of a problem. "There's no point in being quantitatively right if you're qualitatively wrong."
I want to finish by recalling three examples of wrong unconscious assumptions that I came across during my research career. The first two are central to atmospheric and climate science. I am sure Professor YE would have recognized them. They are from past history and not, as far as I know, problematic today. But I think they are instructive. The third is from biology. Professor YE might have recognized this third example as well, if only because it has greatly impeded progress in understanding our own human nature——for one thing misinterpreting and distorting what Charles DARWIN said on that topic——and it still impedes progress today, sometimes quite severely. Of these three assumptions at least the first two must, I feel sure, have been unconscious, because their wrongness becomes so obvious as soon as they are made conscious. As for the third, I must leave it to my biological colleagues to assess it.
Assumption 1: correlation implies causality. This also comes in a harder mathematical version, which I sometimes call the "A=B assumption" and which is actually the form of it that I myself have encountered most closely. It says that when you have an equation A=B, implying of course that a variable A is perfectly correlated with another variable B, it also implies that B causes A, or that B drives A. That assumption can be seen as obviously wrong, indeed silly, once it is made conscious, because one can equally well write the equation as B=A. I suspect that there might be an unconscious tendency to confuse the equation A=B with a line of computer code A=B, which looks the same but means something quite different.
One counterexample would be slowly pushing a dinner plate along a table. To a good approximation one has a balance between the applied force A and the friction force B. But it makes no sense to say that B causes A. You may laugh, but when working on the ozone problem I encountered a closely similar assumption, again and again, about what causes global-scale circulations like that in Fig. 2. They are thermally driven, it was argued, because to a good approximation we have an equation A=B in which B is a mean diabatic heating rate, and A is the static stability times the transformed Eulerian-mean vertical velocity. The trouble with the argument is that, because of the way infrared radiative cooling works, the stratosphere is a thermally-relaxing system. This means that B has a role rather like the friction on the dinner plate. So it is best regarded as part of the response to whatever is driving the circulation, which turns out to be more aptly described as a mechanical pumping action due to wave-induced angular momentum transport. That pumping action has been thoroughly studied using a hierarchy of conceptual, analytical, numerical, and fluid-laboratory models. It can usefully be called "gyroscopic pumping" as a reminder that Coriolis effects are crucial. "Ekman pumping" is a special case of it.
Assumption 2: small implies unimportant. That too is obviously wrong once you make it conscious because, again, it is so easy to find counterexamples. One of these is the ordinary audio amplifier. The small input signal is important. Yet, especially during the first half of my career, I repeatedly encountered a mindset that seemed to be a version of Assumption 2. It was the idea that energy budgets are the Answer to Everything, "the" way to understand how the atmosphere works. For an audio amplifier, the implication would be that only the output stage and the large currents from the power supply are important, the input signal being so tiny that its effects must quite obviously be negligible.
Again, you may laugh, but think again about the ozone hole, and the well-funded disinformation campaign that tried to discredit the science we did. Some of the campaigners had impressive-looking scientific qualifications. Yet one of the arguments they used was that the amounts of chlorofluorocarbons in the atmosphere are so tiny by comparison with the amount of ozone that the chlorofluorocarbons couldn't possibly be important, and therefore need not be regulated. Of course most of us can clearly say why that argument is wrong. An amplifier mechanism is involved. It is called chemical catalysis.
I think most of us also recognize that the climate system is an amplifier, albeit slowly-responding, very noisy, very nonlinear, and fearsomely complex. The input signals include small injections of CO2, and small changes in the Earth's orbit. The response, over long time scales, is huge. It is well known and thoroughly cross-checked that sea levels have gone up and down by as much as 120 m or so, in the late Pleistocene. (And it bothers me that people often talk about "the" climate sensitivity to CO2, with no mention of the many nonlinearities that are suppressed in model experiments but not in the real climate system——producing many different sensitivities over different time scales, some of which are so long, relative to human societal time scales, that the changes due to human activities are effectively permanent and irreversible.) In my e-book I try to promote an "amplifier metaphor for climate," and to point out that the human-induced CO2 input signal should be measured not against total atmospheric CO2, as is usually done, but more appropriately against the natural range of variation of atmospheric CO2, ∼100 ppmv, which shows up so clearly and unequivocally in late Pleistocene ice-core records.
Assumption 3: dynamical mechanisms having disparate timescales cannot interact strongly. I call this the multi-timescale fallacy. Its wrongness should be obvious because, again, counter-examples are so easy to find, and so plentiful. The ozone-hole and climate problems are very clear counter-examples, as well as all the wave-mean interaction problems I have worked on. And there are others far simpler. Perhaps the simplest is gas pressure and temperature. When you pump up your car or bicycle tyres, the changes in pressure and temperature are exceedingly slow by comparison with the fast molecular collisions involved. The slow-fast interaction is all-important.
So it was strange for me to discover, in my studies of the biological research literature, discussed at greater length in my e-book, and in my conversations with leading biological researchers, that Assumption 3 is very commonly made. It shows up, for instance, in the literature on evolution, including that on the evolution of our own ancestors. And yet there is, for instance, a powerful case (starting with linguistic studies in Nicaragua) that human evolution, including the development of our language ability, must have depended on strong interactions between very slow and very fast processes, violating Assumption 3——in particular slow genomic evolution and fast cultural evolution.
The possibility that there could be strong slow-fast interactions of this kind seems to have gone almost unrecognized in the literature on biological evolution, with a few exceptions such as the writings of the great paleoanthropologist Phillip TOBIAS. Indeed, one often reads heavy warnings against confusing the slow with the fast, as if it were self-evident that the two could not possibly interact. This is sometimes designated as confusing "ultimate causation" (slow) with "proximate causation" (fast). It is like saying that just because gas pressure changes are so slow, and molecular collisions so fast, they must be considered as completely separate processes with no significant interaction. The related assumption that genes govern everything——motivating the choice of the word "ultimate"——is even worse, if anything, like saying that slow pressure changes govern fast molecular collisions, with no back-reaction the other way.