I’ve been interested in this book by Hugo Mercier and Dan Sperber for a while and with the library doing business again, I got my chance.

The book concerns the human faculty of reason. What is it? How does it work? What evolutionary context produced it? Etc.

It turns out that these are tricky questions. Most people tend to think of reason as the goal of thinking or something like that. It’s necessarily vague. There is a linguistic quirk in that reasoning (in English and some other languages) seems to produce reasons, justifications for causes. Normally people have the impression that they think about something using reason and then from that cogitation, produce reasons (to do or not do something, to support something or to withhold support, etc.) But this book is covering the interesting hypothesis that: reasons appear in your mind first, and reason is a faculty marshaled post hoc only to justify the reasons.

There are many good, uh, reasons to believe this is in fact what is going on. It turns out that there are many glaring problems with the idea that "reason cleverly computes answers", which the book calls the "intellectualist" model. As a poignant example, I thought that the following quote was an interesting way to frame the problem: (p21) "This very lack of agreement among specialists [on reason!] who, one hopes, are all good reasoners, is particularly ironic: sophisticated reasoning on reasoning does not come near providing a consensual understanding of reasoning itself."

Why would our minds do this weird thing? The hypothesis is that reason is a communication strategy to help secure cooperation in social situations. Reasoning is a way to get other people in your clan to feel the same way as you do.

The title of the section starting on p123 is a good micro summary of the book’s entire premise Reasons Are For Social Consumption.

And that’s mostly it. You can stop here and just ponder that for the rest of your life. If you really find the topic fascinating, I’ve pulled out excerpts that I found particularly interesting. If you’re still intrigued by the notion after reading them all, I do recommend the book!

I thought of computer programming when I read this: "As they become more complex, reasoning tasks rapidly become forbiddingly difficult and performance collapses." (p26)

I also thought about programming reading this: "It takes patience and training for a painter to see a color on the canvas as it is rather than as how it will be perceived by others in the context of the whole picture. Similarly, it takes patience and training for a student of logic to consider only the logical terms in a premise and to ignore contextual information and background knowledge that might at first blush be relevant. … Should those of us who do not aspire to become painters or logicians feel we are missing something important for not sharing their cognitive skills? Actually, no." (p33) This also reminds me of the minds of lawyers.

I’m a David Hume fanboy and he doesn’t disappoint on this topic which the book quotes him on. Disagreeing with Descartes who believed that "animals don’t think", Hume says (p51), "Animals, therefore, are not guided in these inferences by reasoning: Neither are children: Neither are the generality of mankind, in their ordinary actions and conclusions: Neither are philosophers themselves, who in all the active parts of life, are, in the main, the same with the vulgar… Nature must have provided some other principle, of more ready, and more general use and application; nor can an operation of such immense consequence in life, as that of inferring effects from causes, be trusted to the uncertain process of reasoning and argumentation." If you cant take his word for it on that topic, well, you’ll be hard to convince. The book really is a massive exploration of this idea elaborated by Hume and others.

The book seems to try to push one of my long time assertions into the mainstream: that our minds are composed of multiple cognitive actors. On page 74, "In psychology, the mind had long been viewed as a unitary general intelligence with an integrated memory, and connected to the world through various sensory and motor organs. Today, evidence and arguments from neuroscience, developmental psychology, and evolutionary psychology has favored a view of the mind as an articulation of a much greater variety of autonomous mechanisms."

An interesting discussion of how humans have a special need to "mind read". "We attribute mental representations to one another all the time. We are often aware of what people around us think, and even what they think we think. Such thoughts about the thoughts of others come to us quite naturally." (p94) Indeed. As I read this I found it to be a glaring deficiency in all AI research I’m familiar with. Only the crudest recommendation engines exist and they can only seem impressive because the task is so amazingly complex, not because they come close to human levels of competence. The book notes that human infants can correctly assess what people are thinking even when the subject whom they are thinking about has been deceived and thinking something clearly incorrect. Another very interesting cognitive challenge that I thought would be extremely difficult for extant AI agents was (p112) to ask it to justify its beliefs — even if it was wrong. It turns out humans are extremely good at this — being wrong hardly seems to impair us!

This made me think of medical doctors. And certain "news" channels. "Our intuitions about good and bad explanations are not the same as our intuitions about the things explained. … Our intuitions about explanations exploit properties such as cogency, generality, or coherence that are properties of the explanations themselves and not of the things explained." (p103)

This very sensible point defending the thesis caught my attention. "When you argue, you do not stop using language in the normal way, nor does you audience refrain from interpreting your statements using the same pragmatic capacities they use all the time. In argumentation, ordinary forms of expression and interpretation are not overridden by alleged rules of reasoning that might be compared to rules of arithmetic. Rules of arithmetic are taught and are not contested. There is no agreement, on the other hand, on the content and very existence of rules of reasoning. What is sometimes taught as rules of reasoning is either elementary logic or questionable advice for would-be good thinking or good argumentation (such as lists of fallacies to avoid, which are themselves fallacious)." (p164) I immediately thought of programming where this is sometimes not true — there are correct rules of doing it right and doing it wrong. There may be an objective right answer. But where the goal is less constrained, even programming can be quite intuitive and artistic. Engineering in general also shares this; its unnatural but necessary communication style seems unpleasant for some people while reassuring and comfortable to others. On p220 engineers are cited specifically as the kind of people for whom argumentation — which becomes practically synonymous with reasoning — can produce effective results. In the example given, Engineer A argues for a suspension bridge and Engineer B argues for a cantilever bridge; by both trying to show the advantages of their strategy, the optimal strategy can plausibly be highlighted. Among engineers, this does happen. Less so for normal people. Engineers must be less sensitive to others boldly contradicting the validity of their thinking. Unlike, say, a lawyer who expects arguments from well defined adversaries, an engineer must be constantly ready for this from within their own team.

On p206 the book brings up the weird case of Nobel laureate Linus Pauling who was clearly a genius and clearly good at "reasoning". However, he also went a bit mad using his prodigious capacity to argue effectively to make a strong case that vitamin C is some kind of weird panacea that could do things it probably can’t such as cure cancer. It’s a reminder that the smartest people are not above the all too human risk of being wrong; they differ by being especially good at convincing everybody else to be wrong too.

A book that cites Hume is on the right track in my opinion but when Karl Popper is brought in to illuminate things, I am already on board. Here’s the book reminding us what proper "science" is according to Popper, who, in my opinion, is correct: "Scientists produce theories that are at risk of being falsified. They improve their theories by looking for falsifying evidence, by rejecting falsified theories, and by holding only to theories that have withstood repeated attempts at falsifying them." (p211) It always amazed me how many "scientists" I encountered at university research institutions who did not have a clue about this assertion.

The book’s main premise is nicely encapsulated on p235, "The fact that people are good at evaluating others' reasons is the nail in the coffin of the intellectualist approach. It means that people have the ability to reason objectively, rejecting weak arguments and accepting strong ones, but that they do not use these skills on the reasons they produce." When people produce reasons, they are biased towards their own objectives; they have a relatively poor ability to conceive of proper criticism of their own reasons. The reasons people can reliably produce proper unbiased criticism of, are those of other people. It’s a good sign for that theory that I’m having a hard time coming up with much a criticism of that idea!

Reasoning is traditionally thought of as what the book calls an "intellectualist" process where clever rational logical thinking produces correct answers that guide your actions and feelings. However, "Not only does reasoning fail to fix mistaken intuitions, as [the intellectualist] approach claims it should, but it makes people sure that they are right, whether they are right or wrong, and stick to their beliefs for no good reason. Historical examples attest that these are no minor quirks magnified by clever experiments, but real phenomena with tragic consequences." (p244)

Page 250 has some interesting thoughts on how our natural faculty for reason may now be bent into strange contortions well beyond the evolutionary service it provided. The analogy is how our ability to look at and quickly discern small shapes was always there for a variety of good effects, but today we have this crazy thing called literacy that to other animals (like your dog) must seem bonkers. Our reasoning faculty is really being stretched with things like STEM.

The book is full of interesting psychology studies. One described on p252 demonstrates what I call the "Mitch McConnel Effect". They gave people a questionnaire and then through some clever sleight of hand immediately changed the people’s answers to be the opposite of what the subjects had actually selected. "Fewer than half the participants noticed that something was wrong with the new answers. The majority went on justifying positions contrary to those they had professed a few minutes earlier, especially if their opinions weren’t too strong to start with."

This important summary elaborates on these studies (p255): "Here’s the common thread in all these results: in each case, reason drives participants toward the decision that is easier to justify." Note that easier to justify is not at all correct. The critical point here is that with two competing theories with no other distinguishing merit, a person is more likely to believe in the theory that they feel will be easier to convince other people is true. That’s a subtle but important insight.

"Our reasons for acting the way we do shouldn’t just be good reasons; they should be reasons that are easily recognized as good. … Trying to look rational, even at the price of some practical irrationality, may be the most rational thing to do." (p257) Reminds me of enterprise thinking, e.g. "no one ever got fired for buying [the ordinary brand]".

"Children’s reasoning shares two basic features of adult reasoning: myside bias and low evaluation criteria for one’s own reasons." I read that and mentally recast it as, "Adult reasoning is frighteningly similar to the reasoning of children." (p292)

Page 301 mentions a 2001 article by Jonathan Haidt called "The Emotional Dog And Its Rational Tail"; it is paywalled, but here is a readable version. However the title is enough to perfectly capture the entire essence of the book. This book could be reasonably described as a thorough vindication of the article’s premise — a surprising hypothesis not at all falsified!

Page 318 notes a study that showed scientists to be as biased (in this experimental context, perhaps not generally) as a group of ministers. "His observations showed that scientists reason to write off inconvenient results. When an experiment has a disappointing outcome, researchers do not reason impartially, questioning their initial hypothesis and trying to come up with a new one. Instead, they are satisfied with weak arguments rescuing the initial hypothesis…"

Discussing where reasoning is good and not so good, "We are as good at recognizing biases in others as we are bad at acknowledging our own. Perhaps this explains why many people can both hold onto an intellectualist position (for themselves and some kindred spirits) and firmly believe that reason is biased and lazy (particularly in individuals who disagree with them)." (p330)

There it is. Once you hear this simple idea, if you’re like me, it makes immediate sense and you start to see the world in a new way. When you’re alone, you pretty much do what you feel like you should do; it’s only around other people that you put together a "logical" case for why you’re behaving that way. By understanding that reasoning is a communication and coordination strategy I think effort applied towards it can be organized to better satisfy the real goal. But if you disagree, well, I guess I need more work on my communication strategy!