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What Intelligence Tests Miss: The Psychology of Rational Thought

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This is an interesting book that expands the debate regarding IQ tests. The supporters of IQ tests such as Charles Murray in Bell Curve: Intelligence and Class Structure in American Life (A Free Press Paperbacks Book) and Arthur Jensen in The g Factor: The Science of Mental Ability (Human Evolution, Behavior, and Intelligence) state they fully capture cognitive capabilities and predict social outcome. But, the detractors such as Howard Gardner in Multiple Intelligences: New Horizons in Theory and Practice and David Coleman in Emotional Intelligence: 10th Anniversary Edition; Why It Can Matter More Than IQ state IQ is too narrow a concept and IQ tests are inaccurate. Stanovich agrees with the supporters that IQ can be measured and it captures specific cognitive skills. And, that it has causal social outcome implications. He disagrees with detractors that we need to expand the concept of intelligence and that IQ tests are irrelevant. However, he advances that IQ tests do not measure rational decision making ability.

Stanovich refers to IQ as the Algorithmic Mind and rationality as the Reflective Mind. He indicates that the correlation between the two is low. Many people have the equivalent of a powerful computer inside their brain. But, they are surprisingly poor "computer user" of that brain power. He mentions Georges Bush, Jr. who was very intelligent as measured by IQ tests. But, he was not a proficient thinker as he was dogmatic, ill informed, impatient, and prone to rash decisions sometimes associated with devastating outcomes. Stanovich describes Bush condition as Dysrationalia or someone who is less rational than his IQ would suggest.

Stanovich advances that our thinking flaws have an evolutionary source. Evolution is concerned with maximizing survival through procreation. This is associated with quick thinking processes instead of the slower cogitating necessary for complex rational decisions.

Stanovich explores the thinking flaws that prevents us from thinking rationally. They include framing, anchoring, biases, extracting erroneous patterns, discounting future benefits excessively. Here, his references include Scott Plous excellent The Psychology of Judgment and Decision Making and Dan Ariely Predictably Irrational: The Hidden Forces That Shape Our Decisions.

Stanovich suggests we make mental mistakes for several different reasons. First, we are mentally lazy looking for the most immediate solution withouth engaging our higher level thinking processes (algorithmic and reflective thinking). Second, we lack the knowledge to interpret the data rationally (mindware gaps). Third, our rationality falls victim to irrational beliefs: creationism, astrology, Ponzi schemes, etc... (contaminated mindware).

Our lack of adequate rational thinking can have devastating results. This is true in personal finance. Overconfidence in one's knowledge and skills, fitting patterns where none exist, and loss aversion cause the majority of investors to loose money in the stock market. This is even true of investors who invest in mutual funds yet whose returns are far worse than the mutual funds they invest in. This is because they invest in and cash out at exactly the wrong time (buy high and sell low). Here, the author does support the Efficient Market Hypothesis and states that most investors are better off buying and holding an index fund than trading. For more on this subject, I recommend Malkiel's A Random Walk Down Wall Street: The Time-Tested Strategy for Successful Investing. Besides personal finance, lack of rational thinking has dire consequences in foreign policy, and medicine (check out "How Doctors Think" to study this issue further).

In chapter 10, he covers the main mindware gaps, or the quantitative knowledge we often lack to make rational decision. These tools include the scientific method, probability theory, and Bayesian statistics (his section on this topic is arduous for an easier explanation read instead Calculated Risks: How to Know When Numbers Deceive You. Within this chapter he also covers the thinking temperaments that make us good rational thinkers. This includes the ability to accept uncertainty, being open-minded, intellectually investigative, and humble. Such a temperament will allow one to practice sound critical thinking.

Contaminated mindware includes Ponzi schemes, recovered memory theory, conspiracy theories, tax-evasion schemes, win-the-lottery scams, fraudulent investment schemes, Holocaust denying, UFO abductions, Intelligent Design and creationism, religious fundamentalism among others. He indicates that believers in such contaminated mindware have often high IQs. He refers to many studies confirming that terrorists are among the best educated individuals within their religious communities. See Alan Krueger's What Makes a Terrorist: Economics and the Roots of Terrorism (New Edition).

In the last chapter, he recommends we teach rational thinking mindware in high school and college. Charles Murray in Real Education: Four Simple Truths for Bringing America's Schools Back to Reality agreed. College curriculum should include mandatory classes in statistics, logic, and philosophy so that we all become better decision makers.

He also recommends that social policies guide us to make the better choice so that society as a whole benefit from rationality despite our being irrational. This entails making the optimal choice the default selection when we are to choose to be an organ donor or participate in our company's 401K. By doing so, our society would save hundred of thousands of lives (more available organs) and improve the financial welfare of millions of retirees. This is called libertarian paternalism by Richard Thaler who wrote an entire book on the subject: Nudge: Improving Decisions About Health, Wealth, and Happiness.

This book will make you a better decision maker by making you aware of your own blind spots whether they are due to mindware gaps or contaminated mindware.

We are all familiar with the phenomenon of those who have high IQ's doing things that seem stupid. This leads to the distinction between "book smarts" and "street smarts," but strangely enough, we call BOTH of these things intelligence. We recognize both the absent-minded professor and the low IQed entrepreneur as "intelligent." How, though, can the term "intelligence" apply to two seemingly non-correlated things (being book-smart and street-smart)?

Psychologist Keith Stanovich has an interesting idea: maybe "intelligence tests" measure intelligence (as traditionally defined) but not a wholly different faculty of rationality. To Stanovich, the difference between intelligence and rationality is the difference between the "algorithmic mind" and the "reflective mind," or, the difference between the ability to employ algorithms and the ability to think about and CRITICALLY employ algorithms. (I might say that intelligence may be the ability to map or write a sentence and rationality is the ability to formulate arguments and write a persuasive essay.)

The first half of Stanovich's book is dedicated to showing that while IQ tests are a valid measure of a faculty of general intelligence (he does not deny that IQ tests measure a very real thing), it simply does not measure all that we understand to be good thinking.

Stanovich, though, is also a critic of those like Gardner and Sternberg who want to add to the number of "intelligences" (musical intelligence, naturalistic intelligence, creative intelligence). These things, he says, inadvertently beatify the term "intelligence" to be a be-all-end-all that it is not (by implying that any good mental work must be called an "intelligence" rather than a "talent," "skill" or "proclivity.") Instead, Stanovich makes the point that intelligence is simply one component of good thinking. The other, often overlooked, ingredient is rationality (and he alludes to several studies which show these two faculties are not very positively correlated. One can have high amounts of one and low amounts of the other.)

What I thought and hoped Stanovich would do next - what he did not do - is offer a sense of how we can test for RQ (rationality quotient). While the first half makes the case very well that rationality should be valued and tested every bit as much as intelligence, he does not follow it up by showing how such a thing might be done.

Instead, Stanovich devotes the second half of this book largely to cataloguing and demonstrating "thinking errors" that distinguish rational from irrational thought. For example, humans are "cognitive misers" by nature, who like to make decisions based often on first judgments and quick (rather than thorough) analysis (a likely evolutionary strategy, as ancestors that were quick and somewhat accurate probably did better than those who were slow and very accurate). Also, humans often put more emphasis on verification than falsification, and fail to consider alternative hypotheses in problems, preferring often to go with the most obvious answer.

All of these, while interesting, have been better and more thoroughly documented in other books by decision theorists and psychologists. All Stanovich needed to do was refer us to these, at most, devoting a chapter or two to examples. There is more important work for Stanovich to do then rehash what we can just as soon read elsewhere. Instead, I think he sh old have begun outlining ideas on how to test for rationality. What would such tests look like? How would such tests affect our educational system (focused, as it is, on IQ)? What would test questions even look like and how can they be adjusted for by age/grade level? Are there pitfalls?

None of these questions were answered, and Stanovich's argument is the worse for it. Stanovich himself notes that one big reason for IQ's predominance in the psychometric world is that it is measurable (which is a big strike against many of Gardner's "multiple intelligences"). Ironically, Stanovich's failure to suggest ways to measure RQ will likely have the same effect for his idea as it had for Gardner's.

It is a shame, though. As an educator concerned both with the undeserved predominance of IQ and also the failure of concepts such as Gardner's "multiple intelligence" to offer a serious challenge, I quite like Stanovich's germinal idea. As we all know that rationality is a key component to good thinking, and it is hard to think that it is positively correlated to IQ, it would be interesting to find a way to measure RQ as a valid supplement to IQ. It is simply too bad this book did not explore the practical questions involved with his tantalizing suggestion.

I agree on the points made already, including, good start by separating rational thinking from raw intelligence in the sense of processing power, then a propensity to present too many examples of faulty reasoning already made in the literature. I will focus on additional points not mentioned by other reviewers.

What this book gets right:
- stressing a clear distinction between IQ and rationality
- presenting a taxonomy of thinking processes and associated thinking errors according to current cognitive science

Where this book does not so well:
- examples for irrationality often strangely unconvincing or muddled with issues of preference over raw rationality
- repetition of arguments instead of fleshing them out (the endnotes are better written than the main text because here the authors does not try to pander to the 'average' reader by diluting his argument and finding examples from sports etc)
- creation of unnecessary neologisms ("contaminated mindware" instead of "questionable beliefs")

Where this book fails:
- failure to clearly define elements of rationality beyond the labels "instrumental" and "epistemic" and an arbitrary collection of good thinking habits
- failure to come to terms with, or even mention, the problem of volition - who is the controller, what would propel him to override/control his instincts, in which situations is rational thought it the 'right' choice, are there situations where it is not helpful, can such a choice even be determined a priori etc.
- complete failure to assess the issue of the normative in the discussion of rationality. Every so often, examples slip in where the author seems unaware that what he labels irrational beliefs or thinking habits, may actually be legitimate choices, differences in opinion, differences in the assessment of long term effect, probabilistic trade offs in energy spent etc.
- the author seems to assume that 'correct' meaning - semantics - can be created by the 'correct' algorithmic processing of data. I find this worldview a bit simplistic to say the least.

As a result, the book clearly establishes what I also hold as somehow self evident, that the means to achieve an end (intelligence) are different from their owner's propensity to use them properly (lazy or faulty reasoning habits leading to faulty thinking or faulty conclusions from existing data). But the book fails to distinguish rationality from issues that are fundamentally semantic or normative, from personal choices, from probabilistic, evolutionary heuristics that may not be rational but justified because on average they work. There is little philosophical or epistemological depth, little awareness that maybe even a better algorithmic application may not be the final solution yet to cognition. The author simply assumes that proper application of algorithmic reasoning somehow would solve most "problems" - and falls into a rather Hayekian "scientism", or "pretense of knowledge" kind of trap in his assumptions about what even science can really know about the world.

That being said, as another reviewer has pointed out - it is a rare book that goes all the way to try and dethrone IQ with very good, hard arguments, for this I commend the author, it is worthwhile to read, and it may still be a good book to use in teaching. Too bad it is incomplete and itself somehow biased towards viewing as rationality as all one would ever need to live the good life.

I urge you to read this book. I especially strongly encourage you if you have a relatively high measured IQ and are in a position of power. It might start to show you how to be able to exercise this power more effectively. Specifically, it would highlight to you many of the cognitive errors you are undoubtedly prone to, despite your IQ and past education. It might provide the start of a necessary re-education. I would hope that this book soon becomes part of the mandatory curriculum at West Point, Harvard Business School, Yale (see below), Oxford, Cambridge, Sorbonne and other places where intelligence ('smarts') and knowledge has sometimes been emphasised at the expense of rationality and intellectual curiosity.

The book continues to answer the question that has always intrigued me. Why do many of the high IQ fast processing 'smart' people that I have known, actually often have quite stupid beliefs (like astrology) or perform so poorly in their chosen jobs: 'the brightest and the best' that for example gave us the Vietnam War or collateralized debt obligations. Explanations of lack of emotional intelligence or moral failings have seemed partial to say the least. The virtue of Stanovich's book is that he locates a wonderful lode of explanation for this variance in the emerging research on rationality arising out of Kahnemann and Tversky's work on decision making. Indeed he uses a great topical example to get started: George Bush, who it appears probably has a higher than might be thought IQ of around 120 but lacks a whole array of qualities for rational thought: such as willingness to question and test his own beliefs, overconfidence, lack of intellectual curiosity etc. that go a long way to explain the disaster of his presidency. We should be very cautious about the idea that an Obama team of the brightest and best high IQ elite school folk is the answer. There needs to be major cognitive reform across the whole of government, business and military in line with Stanovich's prescription. The greatest danger to the incoming administration is not lack of IQ but lack of rationality as Stanovich so ably defines it.

So use this book to unfreeze your thinking about your own thinking abilities. Use it to develop a check list of the likely shortfalls you are subject to. Use it if you teach to re-shape what you teach. Use it to make better decisions in your personal, financial and business life. And I really mean use it: you will not overcome your natural mental short cuts that Stanovich so mercilessly dissects unless his approach becomes a conscious, overt, disciplined part of how you make the few key decisions each year that determine the future course of your life.

This book is an excellent data driven antidote what I see as the major shortcomings of Malcolm Gladwell's 'Blink' and other books that suggest we follow our gut.

My one worry about this book is how it will reach those it most needs to reach: the overconfident, highly intelligent, highly educated but deeply dysrational? I hope there is a paperback publisher wise enough to speed this book into the mass market and I think the titling should be reversed: what is most profound about this book is not what is missing from IQ tests but the fundamental project of cognitive reform around improved rationality and driving out dysrationalia from public life.

This book is by the way a perfect complement to Richard Nisbett's book Intelligence and How to Get It. Together they reshape the concept of intelligence: its heritability, its malleability and its limitations and the need to stretch far beyond it into true rationality

Stanovich presents extensive evidence that rationality is very different from what IQ tests measure, and the two are only weakly related. He describes good reasons why society would be better if people became more rational.

He is too optimistic that becoming more rational will help most people who accomplish it. Overconfidence provides widespread benefits to people who use it in job interviews, political discussions, etc.

He gives some advice on how to be more rational, such as thinking the opposite of each new hypothesis you are about to start believing. But will training yourself to do that on test problems cause you to do it when it matters? I don't see signs that Stanovich practiced it much while writing the book. The most important implication he wants us to draw from the book is that we should develop and use Rationality Quotient (RQ) tests for at least as many purposes as IQ tests are used. But he doesn't mention any doubts that I'd expect him to have if he thought about how rewarding high RQ scores might affect the validity of those scores.

He reports that high IQ people can avoid some framing effects and overconfidence, but do so only when told to do so. Also, the sunk cost bias test looks easy to learn how to score well on, even when it's hard to practice the right behavior - the Bruine de Bruin, Parker and Fischhoff paper than Stanovich implies is the best attempt so far to produce an RQ test lists a sample question for the sunk costs bias that involves abandoning food when you're too full at a restaurant. It's obvious what answer produces a higher RQ score, but that doesn't say much about how I'd behave when the food is in front of me.

He sometimes writes as if rationality were as close to being a single mental ability as IQ is, but at other times he implies it isn't. I needed to read the Bruine de Bruin, Parker and Fischhoff paper to get real evidence. Their path independence component looks unrelated to the others. The remaining components have enough correlation with each other that there may be connections between them, but those correlations are lower than the correlations between the overall rationality score and IQ tests. So it's far from clear whether a single RQ score is better than using the components as independent tests.

Given the importance he attaches to testing for and rewarding rationality, it's disappointing that he devotes so little attention to how to do that.

He has some good explanations of why evolution would have produced minds with the irrational features we observe. He's much less impressive when he describes how we should classify various biases.

I was occasionally annoyed that he treats disrespect for scientific authority as if it were equivalent to irrationality. The evidence for Big Foot or extraterrestrial visitors may be too flimsy to belong in scientific papers, but when he says there's "not a shred of evidence" for them, he's either using a meaning of "evidence" that's inappropriate when discussing the rationality of people who may be sensibly lazy about gathering relevant data, or he's simply wrong.

Fundamentally, this book does something I have been consistently looking for; Although I have found and read a number of books on biases in the human brain, this book goes the extra step of prescribing a treatment for those biases. On that basis alone, this book this book is worth the money paid.

I would have loved to get even further value for my money. Make no mistake, it gives a great deal of information on biases in ones own thought patterns and more easily accessible treatment on cognitive rules for detecting when your own biases are going to mislead you - I think the chapter on Bayes Theorem (Which I had the good luck to encounter, sans title, at a very young age) would be particularly useful to those that have not encountered it. A host of other simple 'rule of thumb' algorithms to catch yourself before your instincts lead you to a seemingly logical, but wrong conclusion are equally useful.

That said, probably a third of the book is devoted to defending it's underlying premise - Intelligence Tests measure important things, but but these are overvalued in large part because they are easily quantifiable; Habits of rationality far more important that we could (today) measure and indeed teach them are being ignored in favor of items we have gotten 'used to' measuring, and these habits are costing us. In chapter One, and possibly Two, I happily waded through this argument, a validation of a conclusion I had long ago come to. By Chapter 8, 9, and even into 10 it was a well rehearsed argument the author had already made and I was only reading to see if some new important nugget was added into the mixture. It was not.

Ripping that out could easily have added another 50 pages of more information about cognitive biases and coping strategies for dealing with them that would have increased the practical usefulness by another quarter. Or at least made the book thinner and a better read; either would be an improvement.

Still - Despite looking I have not come across a volume that does quite what this book does. While I would happily pay for a volume two tasked specifically to assisting the reader in spotting their own cognitive biases and developing as a habit the tools to overcome same, even as it stands it is a primer unmatched in my experience.

In a world where certain groups resent logic, confuse science with dogma, and refuse to accept separation of church and state as a founding principle, even in it's present form this book is an asset; I would happily assign 'Of Panda's and People' as reading material to a high school class so long as this book were assigned first.

The book is about the fact that IQ tests are incomplete measures of cognitive functioning. There is, as studies have show, in fact only a low to medium correlation between rational thinking skills and IQ test performance. And because rational thinking skills and IQ are largely independent it is not surprising that intelligent people can easily behave irrationally and hold false and unsupported beliefs. Several things are really interesting about this book. One is the authors insight that we do not need to stretch to non-cognitive domains (to notions as emotional intelligence or social intelligence) to see the lacunae in IQ tests. Another is the very specific and research based analysis of the topic matter. The author presents an elegant and rather comprehensive model of cognitive functioning in which three types of major thinking processes and their interrelations are described: the autonomous mind, the algorithmic mind and the reflective mind.

The autonomous mind refers to rapidly executed, non-consciousness requiring mental processes which are often quick and dirty. The algorithmic mind refers to conscious efficient information processing and is linked to what is usually referred to as fluid intelligence. The reflective mind is linked to rational thinking dispositions and deals with questions such as which goals to choose and why, and what action to take given those goals. Conscious thinking can override unconscious thinking, which is a good thing given the quick and dirtiness of the autonomous mind. The algorithmic mind is required for executing this override and thus very important. But the reflective mind is the process which initiates such an override. People with high IQ may be quite capable of overriding false beliefs and erroneous judgments but it takes the rationality of the reflective mind to initiate such an override.

Although many laymen and psychologists seem to think IQ tests do measure rationality, they actually don't. In fact, intelligence, as measure by IQ tests correlates only low to moderately with rational thinking skills. According to Stanovich, this explains why it is not strange to see intelligent people behave irrationally and hold false and unsupported beliefs. Some real world examples are: intelligent people who fall prey to Ponzi scheme swindlers like Bernie Madoff, a highly educated person who denies the evidence for evolution, a United States president who consults an astrologist, and so forth. Below, I will try to summarize how Stanovich explains rationality and lack of rationality.
What is rationality? Cognitive scientists distinguish two basic forms: 1) instrumental rationality, behaving in such a way that you achieve what you want, and 2) epistemic rationality, taking care that your beliefs correspond with the actual structure of the world. Irrational thinking and behaving is associated with three things.

The first is an overreliance on the autonomous mind which subconsciously and automatically uses all kinds of heuristic to come to conclusions and solve problems. The autonomous mind is fast and very valuable but also very imprecise. It is prone to all kinds ofbiases. Thinking deliberately instead of letting the autonomous mind make judgments cost much more time and energy which is why it is temping no resist.

The second thing which is associated with irrationality is what is called a mindware gap. The term `mindware ` refers to the rules, knowledge, procedures, and strategies that a person has available for making judgments, decisions and solving problems. Lack of such knowledge, etc hinders rationality.

The third thing which is associated with irrationality is something called contaminated mindware, beliefs, rules, strategies, etc that are not grounded in evidence and that are not good for the one who holds them (the host) but which can still spread easily throughout a population. There are several reasons why they can spread easily: 1) they are often packaged in an appealing narrative which promises some kind of benefit to the host, 2) they sometimes ride on the back of other popular mindware which may be more valid by copying superficial characteristics from that mindware, 3) they contain self-replicating instructions (`send this mail on to 10 different people'), 4) they may have evaluation-disabling properties (for instance by claiming that evidence is not relevant or possible, by making belief which is unsupported by evidence into a virtue, by encouraging adherents to attack non-believers, etc). You might think that intelligence would guarantee a good protection against contaminated mindware but this turns out to be wrong. By making narratives complex, highly intelligent people can even become extra attracted to them. Further, studies have demonstrated that intelligent people may be more capable of creating `islands of false beliefs' or 'webs of falsity' by using their considerable computational power to rationalize their beliefs and to ward off the arguments of skeptics.
The last part of the book is devoted to a first attempt by the author to a taxonomy of rationality. Also he makes a plea for shifting the focus in society from intelligence alone to a more balanced attention for intelligence and rationality. He makes it clear that, while discussions about the mutability of intelligence are still going on, there is no doubt at all that rationality is something which can be learned. Also he points at the possibility to design rationality tests and to have institutions take structural measures in order to limit the damaging effects of irrationality.

A very interesting book which deserves to be read by many psychologists and educators.

The subject of "why smart people do dumb things" is becoming pretty hot, with a new book in this genre now seemingly coming out every other day. I think this is actually a healthy trend, since the insights from this literature are genuinely useful and represent perhaps the best that psychology and other human sciences have to offer. This torrent of books may eventually reach the point where separating the wheat from the chaff becomes a challenge, but of course we have these Amazon reviews to help us do that!

Within this crowd of books, I would say that Stanovich's book is among the better ones, and its distinction is that he focuses on the difference between intelligence (as measured by IQ tests) versus rationality ("adopting appropriate goals, taking appropriate action given one's goals and beliefs, and holding beliefs that are commensurate with available evidence"). Coming from Stanovich's cognitive science background, one could roughly say that intelligence is like having good hardware and rudimentary core software (and thus processing power and speed), whereas rationality is like having good application software (and thus ability to effectively perform real-world functions, even if having lesser processing power means that this happens more slowly).

Stanovich spends a lot of time elaborating on the difference between intelligence and rationality, why IQ tests don't measure rationality and in fact divert our attention away from rationality, the various ways in which our software ("mindware") falls short and causes us to act dysrationally (do "dumb things"), how we can become more rational, and why rationality is ultimately important for both individuals and society.

Stanovich covers all of this clearly enough, and I had no difficulty following his arguments and evidence and being convinced by them. But my one main issue with the book is that, while the book topic and content seem aimed at the general reader, the writing style is somewhat stiff and formal, making it seem like Stanovich also felt obligated to cater to the expectations of his academic colleagues. What I mean is that Stanovich tends to spend too much time explaining, justifying, and repeating rather obvious points, and also getting into details which are really only of academic interest, so reading the book can become tedious (the bibliography runs almost 60 pages, with nearly 1000 references which are mostly papers rather than books). Instead, I think the book could and should have been written with a simpler and breezier style, which would have made it just as convincing, but easier to understand and remember and go back to as a reference (not to mention selling way more copies).

Overall, I do think this is a worthy book which I can recommend, but it's best suited for readers who aren't deterred by a somewhat academic writing style.

Professor Stanovich was asking himself the question why smart, i.e. intelligent, people act foolishly, for example, why they make financial decisions that cause them to lose a lot of money. He sees the reason for this in the fact that classical IQ tests just measure one aspect of cognitive functioning, but leave other important aspects out. One of these aspects is, according to Professor Stanovich, rationality, which comprises acting in a way that you get what you most want and holding beliefs reflect the actual structure of the world. Rationality is crucial in decision making and assessing probabilities, but largely independent of intelligence.

He sees one reason for what he calls "dysrationalia" in the fact that humans are cognitive misers, meaning that they unconsciously try to avoid elaborate cognitive processing whenever possible. For example, when making judgments or decisions, humans rely on heuristics rather than thorough analytical processing. This leads to humans losing a lot of money on the financial markets, being easily influenced by advertisements and being outsmarted when buying products. But not only financial decisions are affected by dysrationalia. Irrational thought also influences decisions in other domains like medicine, state affairs, even personnel selection! Other reasons are, according to Professor Stanovich, the lack of probability knowledge and alternative thinking as well as faulty knowledge and beliefs about the world.

So Professor Stanovich identifies three sources of what he calls dysrationalia: mindware gaps, contaminated mindware, and the fact that humans are cognitive misers.

Being a cognitive miser means unconsciously preferring "quick and dirty" to thorough and accurate processing of information because the latter is a lot more effortful, and human brains are lazy. Therefore, humans are very prone to making thinking errors.

Humans are very sensitive to vivid presentations of information. For example, many people consider flying a lot more dangerous than driving a car because of the presentation in the media. However, it is far more likely to die in a car accident than in an airplane crash. This misconception affects, for example, decisions on which means of transportation is used when travelling somewhere.

When humans make estimates on numbers or bargain prices, they use previously learned numbers as anchors. For example, if people want to purchase something, like a car, the first price mentioned (either by the sales person or by the customer) influences the further offers made. But anchoring even happens when the numbers involved are completely unrelated. In an experiment, the number shown by a wheel of fortune in the beginning of the experiment influenced test persons' estimates of the number of African states that are members of the United Nations.

Humans' decisions depend on the way an issue is framed - they make different decisions on the same issue when the issue is presented in different frames. For example, experiments show that if a tax model suggests a bonus for having children, people want the bonus to be the same for high and low income families. But if the same amount of money is labeled as punishment for having NO children, people want high income families to pay more than low income families. This is the case although the numbers are exactly the same, just the frames are different.

These are all heuristics humans use because they are cognitive misers. But, as mentioned before, judgments on the basis of heuristics are not the only reason for dysrationalia. The other reasons are mindware gaps and contaminated mindware.

Mindware comprises rules, knowledge, procedures, and strategies that can be derived from one's memory when making decisions or solving problems. Sometimes people do not have the mindware necessary for making a rational decision or solving a problem appropriately, and this is what Professor Stanovich calls "mindware gap". However, sometimes people have enough or even more than enough knowledge, but it leads to maladaptive actions and resists evaluation. This is what he calls "contaminated mindware". Both concepts, mindware gaps and contaminated mindware, will be explained below.

One example of a mindware gap is the lack of understanding for conditional probabilities. The relationship between them is described by Bayes' theorem. The key idea is that the probability of an event A given an event B (e.g., the probability that one has breast cancer given that one has tested positive in a mammogram) depends not only on the relationship between events A and B (i.e., the accuracy of mammograms) but on the marginal probability (or "simple probability") of occurrence of each event. The likelihood of a woman having breast cancer when her mammogram is positive has therefore to be calculated using both the prevalence rate of the disease and the accuracy of the mammogram. The conditional probabilities can be dramatically different from the unconditional ones, but because most people are not familiar with Bayes' theorem, wrong decisions are likely.

The theorem is of far more practical relevance than one might think. Imagine a company that would like to hire a physicist. Before starting the selection process, they might want to know how likely it is to find a person that does the job well. In order to calculate this probability, they have to take the prevalence of physicists in the population and the accuracy of the selection process they will use into account. Or they might jus exchange the variables in the equation: How accurate does our selection process have to be in order to have a high probability of hiring the right person? The prevalence of the profession in search plays a critical role here, which is often neglected when making decisions on selection processes.

So mindware gaps result from a lack of knowledge. Contaminated mindware, in contrast, results from too much knowledge and complexity. Consider all the literature on "beating" the stock markets, procedures for winning lotteries, or even conspiracy theories. They are stuffed with facts and figures, mathematical formulas, and so on. Therefore, according to Professor Stanovich, people of modest to high intelligence are predisposed to studying them. However, most of these tricks don't work, and in the end, people do not profit from the ideas that appear so smart and scientific at first glance. Irrational beliefs like superstition, but also all beliefs that cannot be proven, are contaminated mindware as well. So contaminated mindware does not reflect the actual world and usually serves someone's purpose, but mostly not it owner's.

So far, this is pretty bad news. However, Professor Stanovich also has a positive message: Rationality can be learned! This means that everyone can take courses that teach them the knowledge necessary for avoiding thinking errors and for closing mindware gaps. Furthermore, there are a number of strategies how to deal with contaminated mindware. Employers can offer further training to their employees in order to improve their rationality. And at this point, intelligence tests might be relevant again: They are good measures for a person's potential to learn new things. Therefore, intelligence test results are likely to predict to a certain amount how easily someone will learn rationality. Humans are not rational by nature, but they can learn it - and isn't this good news?

Ever wonder why your neighbor with the PhD consults the daily horoscope? Keith Stanovich has a pretty persuasive answer. He believes that intelligence tests do not adequately measure rationality, which is more important. Using an exensive list of experiments, Stanovich shows just how irrational people often are, even those with a high I.Q. (he mentions that high percentages of Mensa members believe in astrology and extraterrestrial sightings, for instance). A number of concepts that may not be familiar to the general psychology reader are introduced in this book, but Stanovich never comes off as an arrogant academic. This is a fascinating book that should be read by anyone concerned with the dangers of an irrational world.