"What scientific concept would improve everyone's cognitive toolkit?"

[ZeaLitY]

MAHZARIN R. BANAJI
Richard Clarke Cabot Professor of Social Ethics, Department of Psychology, Harvard University

A Solution for Collapsed Thinking: Signal Detection Theory

We perceive the world through our senses. The brain-mediated data we receive in this way form the basis of our understanding of the world. From this become possible the ordinary and exceptional mental activities of attending, perceiving, remembering, feeling, and reasoning. Via these mental processes we understand and act on the material and social world.

In the town of Pondicherry in South India, where I sit as I write this, many do not share this assessment. There are those, including some close to me, who believe there are extrasensory paths to knowing the world that transcend the five senses, that untested "natural" foods and methods of acquiring information are superior to those based in evidence. On this trip, for example, I learned that they believe that a man has been able to stay alive without and caloric intake for months (although his weight falls, but only when he is under scientific observation).

Pondicherry is an Indian Union Territory that was controlled by the French for 300 years (staving off the British in many a battle right outside my window) and held on to until a few years after Indian independence. It has, in addition to numerous other points of attraction, become a center for those who yearn for spiritual experience, attracting many (both whites and natives) to give up their worldly lives to pursue the advancement of the spirit, to undertake bodily healing, and to invest in good works on behalf of a larger community.

Yesterday, I met a brilliant young man who had worked as a lawyer for eight years who now lives in the ashram and works in their book sales division. Sure, you retort, the profession of the law would turn any good person toward spirituality but I assure you that that the folks here have given up wealth and professional life of a wide variety of sorts to pursue this manner of life. The point is that seemingly intelligent people seem to crave non-rational modes of thinking and the Edge question this years forced me to think not only about the toolkit of the scientist but every person.

I do not mean to pick on any one city, and certainly not this unusual one in which so much good effort is put towards the arts and culture and on social upliftment of the sort we would admire. But this is a town that also attracts a particular type of European, American, and Indian — those whose minds seem more naturally prepared to believe that unprocessed "natural" herbs do cure cancer and that standard medical care is to be avoided (until one desperately needs chemo), that Tuesdays are inauspicious for starting new projects, that particular points in the big toe control the digestive system, that the position of the stars at the time of their birth led them to Pondicherry through an inexplicable process emanating from a higher authority and through a vision from "the mother", a deceased French woman, who dominates the ashram and surrounding area in death more than many successful politicians ever do in their entire lives.

These types of beliefs may seem extreme but they are not considered as such in most of the world. Change the content and the underlying false manner of thinking is readily observed just about anywhere — the new 22 inches of snow that has fallen where I live in the United States while I'm away will no doubt bring forth beliefs of a god angered by crazy scientists toting global warming.

As I contemplate the single most powerful tool that could be put into the heads of every growing child and every adult seeking a rational path, scientists included, it is the simple and powerful concept of "signal detection". In fact, the Edge question this year happens to be one I've contemplated for a while — should anybody ever ask such a question, the answer I've known would be an easy one: I use Green & Swets Signal detection theory and Psychophysics as the prototype, although the idea has its origins in earlier work among scientists concerned with the fluctuations of photons and their influence on visual detection and sound waves and their influence on audition.

The idea underlying the power of signal detection theory is simple: The world gives noisy data, never pure. Auditory data, for instance, are degraded for a variety of reasons having to do with the physical properties of the communication of sound. The observing organism has properties that further affect how those data will be experienced and interpreted, such as ability (e.g., a person's auditory acuity), the circumstances under which the information is being processed (e.g., during a thunderstorm), and motivation (e.g., disinterest). Signal detection theory allows us to put both aspects of the stimulus and the respondent together to understand the quality of the decision that will result given the uncertain conditions under which data are transmitted, both physically and psychologically.

To understand the crux of signal detection theory, each event of any data impinging on the receiver (human or other) is coded into four categories, providing a language to describe the decision:
          Did the event occur?    
          Yes    No
     Yes    Hit    False Alarm
Did the received detect it?              
     No    Miss    Correct Rejection

Hit: A signal is present and the signal is detected (correct response)

False Alarm: No signal is presented but a signal is detected (incorrect response)

Miss: A signal is present but no signal is detected (incorrect response)

Correct Rejection: No signal is present and no signal is detected (correct response)

If the signal is clear, like a bright light against a dark background, the decision maker has good visual acuity and is motivated to watch for the signal, we should see a large number of Hits and Correct Rejections and very few False Alarms and Misses. As these properties change, so does the quality of the decision. Whether the stimulus is a physical one like a light or sound, or a piece of information requiring an assessment about its truth, information is almost always deviates from goodness.

It is under such ordinary conditions of uncertainty that signal detection theory yields a powerful way to assess the stimulus and respondent qualities including the respondent's idiosyncratic criterion (or cutting score, "c") for decision-making. The criterion is the place along the distribution at which point the respondent switches from the saying "no" to a "yes".

The applications of signal detection theory have been in areas as diverse as locating objects by sonar, the quality of remembering, the comprehension of language, visual perception, consumer marketing, jury decisions, price predictions in financial markets, and medical diagnoses.

The reason signal detection theory should be in the toolkit of every scientist is because it provides a mathematically rigorous framework to understand the nature of decision processes. The reason its logic should be in the toolkit of every thinking person is because it forces a completion of the four cells when analyzing the quality of any statement such as "Good management positions await Saggitarius this week".

[ZeaLitY]

NIGEL GOLDENFELD
Professor of Physics, University of Illinois at Urbana-Champaign

Because

When you are facing in the wrong direction, progress means walking backwards. History suggests that our world view undergoes disruptive change not so much when science adds new concepts to our cognitive toolkit, but when it takes away old ones. The sets of intuitions that have been with us since birth define our scientific prejudices, and not only are poorly-suited to the realms of the very large and very small, but also fail to describe everyday phenomena. If we are to identify where the next transformation of our world view will come from, we need to take a fresh look at our deep intuitions. In the two minutes that it takes you to read this essay, I am going to try and rewire your basic thinking about causality.

Causality is usually understood as meaning that there is a single, preceding cause for an event. For example in classical physics, a ball may be flying through the air, because of having been hit by a tennis racket. My 16 year-old car always revs much too fast, because the temperature sensor wrongly indicates that the engine temperature is cold, as if the car was in start-up mode. We are so familiar with causality as an underlying feature of reality that we hard-wire it into the laws of physics. It might seem that this would be unnecessary, but it turns out that the laws of physics do not distinguish between time going backwards and time going forwards. And so we make a choice about which sort of physical law we would like to have.

However, complex systems, such as financial markets or the Earth's biosphere, do not seem to obey causality. For every event that occurs, there are a multitude of possible causes, and the extent to which each contributes to the event is not clear, not even after the fact! One might say that there is a web of causation. For example, on a typical day, the stock market might go up or down by some fraction of a percentage point. The Wall Street Journal might blithely report that the stock market move was due to "traders taking profits" or perhaps "bargain-hunting by investors". The following day, the move might be in the opposite direction, and a different, perhaps contradictory, cause will be invoked. However, for each transaction, there is both a buyer and a seller, and their world views must be opposite for the transaction to occur. Markets work only because there is a plurality of views. To assign single or dominant cause to most market moves is to ignore the multitude of market outlooks and to fail to recognize the nature and dynamics of the temporary imbalances between the numbers of traders who hold these differing views.

Similar misconceptions abound elsewhere in public debate and the sciences. For example, are there single causes for diseases? In some cases, such as Huntingdon's disease, the cause can be traced to a unique factor, in this case extra repetitions of a particular nucleotide sequence at a particular location in an individual's DNA, coding for the amino acid glutamine. However, even in this case, the age of onset and the severity of the condition are also known to be controlled by environmental factors and interactions with other genes. The web of causation has been for many decades a well-worked metaphor in epidemiology, but there is still little quantitative understanding of how the web functions or forms. As Krieger poignantly asked in a celebrated 1994 essay, "Has anyone seen the spider?"

The search for causal structure is nowhere more futile than in the debate over the origin of organismal complexity: intelligent design vs. evolution. Fueling the debate is a fundamental notion of causality, that there is a beginning to life, and that such a beginning must have had a single cause. On the other hand, if there is instead a web of causation driving the origin and evolution of life, a skeptic might ask: has anyone seen the spider?

It turns out that there is no spider. Webs of causation can form spontaneously through the concatenation of associations between the agents or active elements in the system. For example, consider the Internet. Although a unified protocol for communication (TCP/IP etc) exists, the topology and structure of the Internet emerged during a frenzied build-out, as Internet service providers staked out territory in a gold-rush of unprecedented scale. Remarkably, once the dust began to settle, it became apparent that the statistical properties of the resulting Internet were quite special: the time delays for packet transmission, the network topology, and even the information transmitted exhibit fractal properties.

However, you look at the Internet, locally or globally, on short time scales or long, it looks exactly the same. Although the discovery of this fractal structure around 1995 was an unwelcome surprise, because standard traffic control algorithms as used by routers were designed assuming that all properties of the network dynamics would be random, the fractality is also broadly characteristic of biological networks. Without a master blueprint, the evolution of an Internet is subject to the same underlying statistical laws that govern biological evolution, and structure emerges spontaneously without the need for a controlling entity. Moreover, the resultant network can come to life in strange and unpredictable ways, obeying new laws whose origin cannot be traced to any one part of the network. The network behaves as a collective, not just the sum of parts, and to talk about causality is meaningless because the behavior is distributed in space and in time.

Between 2.42pm and 2.50pm on May 6 2010, the Dow-Jones Industrial Average experienced a rapid decline and subsequent rebound of nearly 600 points, an event of unprecedented magnitude and brevity. This disruption occurred as part of a tumultuous event on that day now known as the Flash Crash, which affected numerous market indices and individual stocks, even causing some stocks to be priced at unbelievable levels (e.g. Accenture was at one point priced at 1 cent).

With tick-by-tick data available for every trade, we can watch the crash unfold in slow motion, a film of a financial calamity. But the cause of the crash itself remains a mystery. The US Securities and Exchange Commission report on the flash crash was able to identify the trigger event (a $4 billion sale by a mutual fund), but could provide no detailed understanding of why this event caused the crash. The conditions that precipitate the crash were already embedded in the market's web of causation, a self-organized rapidly evolving structure created by the interplay of high frequency trading algorithms. The Flash Crash was the birth cry of a network coming to life, eerily reminiscent of Arthur C. Clarke's science fiction story "Dial F for Frankenstein", which begins "At 0150 GMT on December 1, 1975, every telephone in the world started to ring." I'm excited by the scientific challenge of understanding all this in detail, because … well, never mind. I guess I don't really know.

[ZeaLitY]

GARY MARCUS
Cognitive Scientist, NYU; Author, Kluge: The Haphazard Evolution of the Human Mind

Cognitive Humility

Hamlet may have said that human beings are noble in reason and infinite in faculty, but in reality — as four decades of experiments in cognitive psychology have shown — our minds are very finite, and far from noble. Knowing the limits of our minds can help us to make better reasoners.

Almost all of those limits start with a peculiar fact about human memory: although we are pretty good at storing information in our brains, we are pretty poor at retrieving that information. We can recognize photos from our high school yearbooks decades later—yet still find it impossible to remember what we had for breakfast yesterday. Faulty memories have been known to lead to erroneous eyewitness testimony (and false imprisonment), to marital friction (in the form of overlooked anniversaries), and even death (skydivers, for example have been known to forget to pull their ripcords — accounting, by one estimate, for approximately 6% of skydiving fatalities).

Computer memory is much more better than human memory because early computer scientists discovered a trick that evolution never did: organizing information according by assigning every memory to a sort of master map, in which each bit of information that is to be stored is assigned a specific, uniquely identifiable location in the computer's memory vaults. Human beings, in contrast. appear to lack such master memory maps, and instead retrieve information in far more haphazard fashion, by using clues (or cues) to what it's looking for, rather than knowing in advance where in the brain a given memory lies.

In consequence, our memories cannot be searched as systematically or as reliably as those of us a computer (or internet database). Instead, human memories are deeply subject to context. Scuba divers, for example, are better at remembering the words they study underwater when they are tested underwater (relative to when they were a tested on land), even if the words have nothing to do with the sea.

Sometimes this sensitivity to context is useful. We are better able to remember what we know about cooking when we are in the kitchen than when we are skiing, and vice versa.

But it also comes at a cost: when we need to remember something in a situation other than the one in which it was stored, it's often hard to retrieve it. One of the biggest challenges in education, for example, is to get children to take what they learn in school and apply it to real world situations, in part because context-driven memory means that what is learned in school tends to stay in school.

Perhaps the most dire consequence is that human beings tend almost invariably to be better at remembering evidence that is consistent with their beliefs than evidence that might disconfirm them. When two people disagree, it is often because their prior beliefs lead them to remember (or focus on) different bits of evidence. To consider something well, of course, is to evaluate both sides of an argument, but unless we also go the extra mile of deliberately forcing ourselves to consider alternatives—not something that comes naturally—we are more prone to recalling evidence consistent with a proposition than inconsistent with it.

Overcoming this mental weakness, known as confirmation bias, is a lifelong struggle; recognizing that we all suffer from it is a important first step.To the extent that we can beware of this limitation in our brains, we can try to work around it, compensating for our in-born tendencies towards self-serving and biased recollections by disciplining ourselves to consider not just the data that might fit with our own beliefs, but also the data that might lead other people to have beliefs that differ from our own.

[ZeaLitY]

ERIC WEINSTEIN
Mathematician and Economist; Principal, Natron Group

Kayfabe

The sophisticated "scientific concept" with the greatest potential to enhance human understanding may be argued to come not from the halls of academe, but rather from the unlikely research environment of professional wrestling.

Evolutionary biologists Richard Alexander and Robert Trivers have recently emphasized that it is deception rather than information that often plays the decisive role in systems of selective pressures. Yet most of our thinking continues to treat deception as something of a perturbation on the exchange of pure information, leaving us unprepared to contemplate a world in which fakery may reliably crowd out the genuine. In particular, humanity's future selective pressures appear likely to remain tied to economic theory which currently uses as its central construct a market model based on assumptions of perfect information.

If we are to take selection more seriously within humans, we may fairly ask what rigorous system would be capable of tying together an altered reality of layered falsehoods in which absolutely nothing can be assumed to be as it appears. Such a system, in continuous development for more than a century, is known to exist and now supports an intricate multi-billion dollar business empire of pure hokum. It is known to wrestling's insiders as "Kayfabe".

Because professional wrestling is a simulated sport, all competitors who face each other in the ring are actually close collaborators who must form a closed system (called "a promotion") sealed against outsiders. With external competitors generally excluded, antagonists are chosen from within the promotion and their ritualized battles are largely negotiated, choreographed, and rehearsed at a significantly decreased risk of injury or death. With outcomes predetermined under Kayfabe, betrayal in wrestling comes not from engaging in unsportsmanlike conduct, but by the surprise appearance of actual sporting behavior. Such unwelcome sportsmanship which "breaks Kayfabe" is called "shooting" to distinguish it from the expected scripted deception called "working".

Were Kayfabe to become part of our toolkit for the twenty-first century, we would undoubtedly have an easier time understanding a world in which investigative journalism seems to have vanished and bitter corporate rivals cooperate on everything from joint ventures to lobbying efforts. Perhaps confusing battles between "freshwater" Chicago macro economists and Ivy league "Saltwater" theorists could be best understood as happening within a single "orthodox promotion" given that both groups suffered no injury from failing (equally) to predict the recent financial crisis. The decades old battle in theoretical physics over bragging rights between the "string" and "loop" camps would seem to be an even more significant example within the hard sciences of a collaborative intra-promotion rivalry given the apparent failure of both groups to produce a quantum theory of gravity.

What makes Kayfabe remarkable is that it gives us potentially the most complete example of the general process by which a wide class of important endeavors transition from failed reality to successful fakery. While most modern sports enthusiasts are aware of wrestling's status as a pseudo sport, what few alive today remember is that it evolved out of a failed real sport (known as "catch" wrestling) which held its last honest title match early in the 20th century. Typical matches could last hours with no satisfying action, or end suddenly with crippling injuries to a promising athlete in whom much had been invested. This highlighted the close relationship between two paradoxical risks which define the category of activity which wrestling shares with other human spheres:

    • A) Occasional but Extreme Peril for the participants.

    • B) General: Monotony for both audience and participants.

Kayfabrication (the process of transition from reality towards Kayfabe) arises out of attempts to deliver a dependably engaging product for a mass audience while removing the unpredictable upheavals that imperil participants. As such Kayfabrication is a dependable feature of many of our most important systems which share the above two characteristics such as war, finance, love, politics and science.

Importantly, Kayfabe also seems to have discovered the limits of how much disbelief the human mind is capable of successfully suspending before fantasy and reality become fully conflated. Wrestling's system of lies has recently become so intricate that wrestlers have occasionally found themselves engaging in real life adultery following exactly behind the introduction of a fictitious adulterous plot twist in a Kayfabe back-story. Eventually, even Kayfabe itself became a victim of its own success as it grew to a level of deceit that could not be maintained when the wrestling world collided with outside regulators exercising oversight over major sporting events.

At the point Kayfabe was forced to own up to the fact that professional wrestling contained no sport whatsoever, it did more than avoid being regulated and taxed into oblivion. Wrestling discovered the unthinkable: its audience did not seem to require even a thin veneer of realism. Professional wrestling had come full circle to its honest origins by at last moving the responsibility for deception off of the shoulders of the performers and into the willing minds of the audience.

Kayfabe, it appears, is a dish best served client-side.

[Radical_Dreamer]

Fascinating! He nails one of my principle objections to economic theory, namely that it is based on faulty assumptions.

[ZeaLitY]

Stuart Firestein
Neuroscientist, Columbia Universtiy

The Name Game

Too often in science we operate under the principle that "to name it is to tame it", or so we think. One of the easiest mistakes, even among working scientists, is to believe that labeling something has somehow or another added to an explanation or understanding of it. Worse than that we use it all the time when we are teaching, leading students to believe that a phenomenon that is named is a phenomenon that is known, and that to know the name is to know the phenomenon. It's what I, and others, have called the nominal fallacy. In biology especially, we have labels for everything - from molecules to anatomical parts, to physiological functions, to organisms, to ideas or hypotheses. The nominal fallacy is the error of believing that the label carries explanatory information.

An instance of the nominal fallacy is most easily seen when the meaning or importance of a term or concept shrinks with knowledge. One example of this would be the word "instinct". Instinct refers to a set of behaviors whose actual cause we don't know or simply don't understand or have access to; and therefore we call them instinctual, inborn, innate. Often this is the end of the exploration of these behaviors, they are the nature part of the nature-nurture argument (a term that itself is likely a product of the nominal fallacy) and therefore can't be broken down or reduced any further. But experience has shown that this is rarely the truth. In one of the great examples of this, it was for quite some time thought that when chickens hatched and they immediately began pecking the ground for food, this behavior must have been instinctive. In the 1920s a Chinese researcher named Zing-Yang Kuo made a remarkable set of observations on the developing chick egg that overturned this idea — and many similar ones. Using a technique of elegant simplicity he found that rubbing heated Vaseline on a chicken egg caused it to become transparent enough to see the embryo inside without disturbing it. In this way he was able to make detailed observations of the development of the embryo from fertilization to hatching. One of his observations was that, in order for the growing embryo to fit properly in the egg, the neck is bent over the chest of the body in such a way that the head rests upon the chest just where the developing heart is encased. As the heart begins beating the head of the chicken is moved in an up-and-down manner that precisely mimics the movement that will be used later for pecking the ground. Thus the "innate" pecking behavior that the chicken appears to know miraculously upon birth has, in fact, been practiced for more than a week within the egg.

In medicine as well, physicians often find technical terms that lead patients to believe that more is known about pathology than may actually be the case. In Parkinson's patients we notice that they have an altered gait and in general that their movement's are slower. Physicians call this "bradykinesia", but it doesn't really tell you anymore than simply saying "they move slower".

Why do they move slower, what is the pathology and what is the mechanism for this slowed movement - these are the deeper questions hidden by the simple statement that "a cardinal symptom of Parkinson's is bradykinesia", satisfying though it might be to say the word to a patient's family.

In science the one critical issue is to be able to distinguish between what we know and what we don't know. This is often difficult enough as things that seem known, sometimes become unknown or at least more ambiguous. When is it time to quit doing an experiment because we now know something, when is it time to stop spending money and resources on a particular line of investigation because the facts are known? This line between the known and the unknown is already difficult enough to define, but the nominal fallacy often obscures it needlessly. Even words like gravity, which seems so well-settled, may lend more of an aura to the idea than it deserves. After all, the apparently very well settled ideas of Newtonian gravity were almost completely undone after 400 years by Einstein's General Relativity. And still today physicists do not have a clear understanding of what gravity is or where it comes from, even though it's effects can be described quite accurately.

Another facet of the nominal fallacy is the danger of using common words and giving them a scientific meaning. This has the often disastrous effect of leading an unwary public down a path of misunderstanding. Words like 'theory', 'law', 'force', do not mean in common discourse what they mean to a scientist. 'Success' in Darwinian evolution is not the same 'success' as taught by Dale Carnegie. Force to a physicist has a meaning quite different from that used in political discourse. The worst of these though may be "theory" and "law" which are almost polar opposites — theory being a strong idea in science while vague in common discourse, and law being a much more muscular social than scientific concept. These differences lead to sometimes serious misunderstandings between scientists and the public who supports their work.

Of course language is critical and we must have names for things to talk about them. But the power of language to direct thought should never be taken lightly and the dangers of the name game deserve our respect.

[ZeaLitY]

BEATRICE GOLOMB. MD
Professor of Medicine, University of California, San Diego

The Dece(i)bo Effect

The Dece(i)bo Effect — think portmanteau of Deceive and Placebo — refers to the facile application of constructs, without unpackaging the concept and the assumptions on which it relies, in a fashion that, rather than benefiting thinking, leads reasoning astray. 

Words and phrases enter common parlance, that capture a concept: Occam's razor, placebo, Hawthorne effect. Such phrases and code-words in principle facilitate discourse — and can indeed do so. Deploying the word or catchphrase adds efficiency to the interchange, by obviating the need for pesky review of the principles and assumptions encapsulated in the word.

Unfortunately, bypassing the need to articulate the conditions and assumptions on which validity of the construct rests, may lead to bypassing consideration of whether these conditions and assumptions legitimately apply. Use of the term can then, far from fostering sound discourse, serve to undermine it.

Take, for example, the "placebo," and "placebo effects." Unpackaging the terms, a "placebo" is in principle something that is physiologically "inert" — but believed by the recipient to be active, or possibly so. The term "placebo effect" refers to improvement of a condition when persons have been placed on a placebo, due to effects of expectation/suggestion.

With these terms well ensconced in the vernacular, Dece(i)bo Effects associated with them are much in evidence.  Key presumptions regarding placebos and placebo effects are more typically wrong than not.

1. When hearing the word "placebo," scientists often presume "inert" - without stopping to ask: what is that allegedly physiologically inert substance? Indeed, even in principle, what could it be??

There isn't anything known to be physiologically inert. There are no regulations about what constitute placebos; and their composition — commonly determined by the manufacturer of the drug under study — is typically undisclosed.  Among the uncommon cases where placebo composition has been noted, there are documented instances in which the placebo composition apparently produced spurious effects. Two studies used corn oil and olive oil placebos for cholesterol-lowering drugs: one noted that the "unexpectedly" low rate of heart attacks in the control group may have contributed to failure to see a benefit from the cholesterol drug. Another study noted "unexpected" benefit of a drug to gastrointestinal symptoms in cancer patients. But cancer patients bear increased likelihood of lactose intolerance — and the placebo was lactose, a "sugar pill." When the term "placebo" substitutes for actual ingredients, any thinking about how the composition of the control agent may have influenced the study is circumvented.

2. Because there are many settings in which persons with a problem, given placebo, report sizeable improvement on average when they are re-queried (see 3), many scientists have accepted that "placebo effects" — of suggestion — are both large in magnitude and widespread in the scope of what they benefit.

The Danish researcher Asbjørn Hróbjartsson conducted a systematic review of studies that compared a placebo to no treatment. He found that the placebo generally does: nothing. In most instances, there is no placebo effect. Mild "placebo effects" are seen, in the short term, for pain and anxiety. Placebo effects for pain are reported to be blocked by naloxone, an opiate antagonist — specifically implicating endogenous opiates in pain placebo effects, which would not be expected to benefit every possible outcome that might be measured.

3. When hearing that persons with a problem placed on a "placebo" report improvement, scientists commonly presume this must be due to the "placebo effect" - the effect of expectation/suggestion.

However, the effects are usually something else entirely. For instance: natural history of the disease, and regression to the mean. Consider a distribution, such as a bell-shape. Whether the outcome of interest is pain, blood pressure, cholesterol, or other, persons are classically selected for treatment if they are at one end of the distribution - say, the high end. But these outcomes are quantities that vary (for instance from physiological variation, natural history, measurement error...), and on average the high values will vary back down — a phenomenon termed "regression to the mean" that operates, placebo or no. (Hence, Hróbjartsson's findings.)

A different dece(i)bo problem beset Ted Kaptchuk's recent Harvard study in which researchers gave a "placebo," or nothing, to people afflicted with irritable bowel syndrome. They administered the placebo in a bottle boldly labeled "Placebo," and advised patients they were receiving placebos, which were known to be potent. The thesis was that one might harness the effects of expectation honestly, without deception, by telling subjects how powerful placebos in fact were - and by developing a close relationship with subjects. Researchers met repeatedly with subjects, gained subjects' appreciation for their concern and listening (as the researchers made clear), and repeatedly told subjects that placebos are powerful. Those placed on placebo obliged the researchers by telling them they had gotten better, moreso than those on nothing. The scientists attributed this to a placebo effect.

But what's to say patients weren't simply telling the scientists what they thought the scientists wished to hear? Such desire to please (a form, perhaps, of "social approval" reporting bias) had fertile grounds in which to operate and create what was interpreted as a placebo effect — which implies actual subjective benefit to symptoms. One wonders if so great an error of presumption would operate were there not an existing term, "placebo effect," to signify the interpretation the Harvard group chose.

Another explanation consistent with these results is specific physiological benefit. The study used a nonabsorbed fiber — microcrystalline cellulose — as the "Placebo" that subjects were told would be effective. The authors are applauded for disclosing its composition. But other nonabsorbed fibers benefit both constipation and diarrhea — symptoms of irritable bowel — and are prescribed for that purpose; psyllium is an example. Thus, specific physiological benefit of the "Placebo" to symptoms cannot be excluded.

Together these points illustrate that the term "placebo" cannot be presumed to imply "inert" (and generally does not); and that when studies see large benefit to symptoms in patients treated with "placebo" (expected from distribution considerations alone), one cannot infer these arose from large benefits of suggestion to symptoms (which evidence indicates may seldom operate).

Thus, rather than facilitating sound reasoning, evidence suggests that in many cases, including high stakes settings in which inferences may propagate to medical practice, substitution of a term — here, "placebo," "placebo effect" — for the concepts they are intended to convey, may actually thwart or bypass critical thinking about key issues, with implications to fundamental concerns for us all.

[ZeaLitY]

BARRY C. SMITH
Director, Institute of Philosophy School of Advanced Study University of London; writer and presenter, BBC World Service series "The Mysteries of the Brain"

The Senses and the Multi-Sensory

For far too long we have laboured under a faulty conception of the senses. Ask anyone you know how many senses we have and they will probably say five; unless they start talking to you about a sixth sense. But why pick five? What of the sense of balance provided by the vestibular system, telling you whether you are going up or down in a lift, forwards or backwards on a train, or side to side on a boat? What about proprioception that gives you a firm sense of where your limbs are when you close your eyes? What about feeling pain, hot and cold? Are these just part of touch, like feeling velvet or silk? And why think of sensory experiences like seeing, hearing, tasting, touching and smelling as being produced by a single sense?

Contemporary neuroscientists have postulated two visual systems — one responsible for how things look to us, the other for controlling action — that operate independently of one another. The eye may fall for visual illusions but the hand does not, reaching smoothly for a shape that looks larger than it is to the observer.

And it doesn't stop here. There is good reason to think that we have two senses of smell: an external sense of smell, orthonasal olfaction, produced by inhaling, that enables us to detect things in the environment such food, predators or smoke; and internal sense, retronasal olfaction, produced by exhaling, that enables us to detect the quality of what we have just eaten, allowing us to decide whether we want any more or should expel it.

Associated with each sense of smell is a distinct hedonic response. Orthonasal olfaction gives rise to the pleasure of anticipation. Retronasal olfaction gives rise to the pleasure of reward. Anticipation is not always matched by reward. Have you ever noticed how the enticing aromas of freshly brewed coffee are never quite matched by the taste? There is always a little disappointment. Interestingly, the one food where the intensity of orthonsally and retronasally judged aromas match perfectly is chocolate. We get just what we expected, which may explain why chocolate is such a powerful stimulus.

Besides the proliferation of the senses in contemporary neuroscience, another major change is taking place. We used to study the senses in isolation, with the greatest majority of researchers focusing on vision. Things are rapidly changing. We now know that the senses do not operate in isolation, but combine at both early and late stages of processing to produce our rich perceptual experiences of our surroundings. It is almost never the case that our experience presents us with just sights or sounds. We are always enjoying conscious experiences made up of sights and sounds, smells, the feel of our body, the taste in our mouths; and yet these are not presented as separate sensory parcels. We simply take in the rich and complex scene without giving much thought to how the different contributors produce the whole experience.

We give little thought to how smell provides a background to every conscious waking moment. People who lose their sense of smell can be plunged into depression and show less sign of recovery a year later than people who lose their sight. This is because familiar places no longer smell the same, and people no longer have their reassuring olfactory signature. Also, patients who lose their smell believe they have lost their sense of taste. When tested, they acknowledge that that can taste sweet, sour, salt, bitter savoury, and metallic. But everything else, missing from the taste of what they are eating, is due to retronasal smell.

What we call taste is one of the most fascinating case studies for how inaccurate our view of our senses is: it is not produced by the tongue alone but is always an amalgam of taste, touch and smell. Touch contributes to sauces tasting creamy, and other foods tasting chewy, crisp, or stale. The only difference between potato chips, which "taste" fresh or stale, is a difference in texture. The largest part of what we call "taste" is in fact smell in the form of retronasal olfaction, which is why people who lose their ability to smell say they can no longer taste anything. Taste, touch and smell are not merely combined to produce experiences of foods of liquids, rather the information from the separate sensory channels is fused into a unified experience of that we call taste and food scientists call flavour.

Flavour perception is the result of multi-sensory integration of gustatory, olfactory and oral somatosenory information into a single experience whose components we are unable to distinguish. It is one of the most multi-sensory experiences we have and can be influenced by both sight and sound. The colours of wines and the sounds food make when we bite or chew them can have large impacts on our resulting appreciation and assessment, and irritation of the trigeminal nerve in the face will make chillies feel "hot" and menthol feel "cool" in the mouth without any actual change in temperature.

In sensory perception, multi-sensory integration is the rule not the exception. In audition, we don't just hear with our ears, we use our eyes to locate the apparent sources of sounds in the cinema where we "hear" the voices coming from the actors' mouths on the screen although the sounds are coming from the sides of the theatre. This is known as the ventriloquism effect. Similarly, retronasal odours detected by olfactory receptors in the nose are experienced as tastes in the mouth. The sensations get re-located to the mouth because oral sensations of chewing or swallowing capture our attention, making us think these olfactory experiences are occurring in the same place.

Other surprising collaboration among the senses are due to cross-modal effects, where stimulation of one sense boosts activity in another. Looking at someone's lips across a crowded room can improve our ability to hear what they are saying, and the smell of vanilla can make a liquid we sip "taste" sweeter, and less sour. This is why we say vanilla is sweet smelling, although sweet is a taste, and pure vanilla is not sweet at all. Industrial manufacturers know about these effects and exploit them. Certain aromas in shampoos, for example, can make the hair "feel" softer; and red coloured drinks "taste" sweet, while drinks with a light green colour "taste" sour. In many of these interactions vision will dominate; but not in every case

. For anyone unlucky enough to have disturbance in their vestibular system they will feel the world is spinning although cues from the eyes and the body should be telling them everything is still. Instead, the brain goes with the combined picture and vision and proprioception fall in line. Luckily, our senses cooperate and we get us around the world, and the world we inhabit is not a sensory, but a multisensory world.