The Skeptics Society & Skeptic magazine


Things Skeptics Knew a Century Ago About How Thinking Goes Wrong

Dec. 29, 2014 by | Comments (1)
skeptic Joseph Jastrow

American psychologist and skeptic Joseph Jastrow. Image courtesy US National Library of Medicine, via Wikimedia Commons.

When better than the final days of the year to reflect on lessons of the past? Today, I’d like to share a small selection of quotes, each written over a century ago, which seem to me to bring the skepticism of our time and that of previous generations into a thought-provoking resonance. These passages employ concepts and jargon that are frequently used by skeptics today. This may strike us as prescient; however, I would argue that this apparent prescience is largely an illusory artifact of our own forgetfulness. In any event, these are a tiny sampling of conversations which were current in skepticism long before any of us were born.

I invite you to gaze into these passages, and reflect for a moment that in some ways the conceptual tools for skeptical examination of paranormal claims have changed little more in a century than the nature of imposture and superstition.

Pretend Medicine

Phineas Taylor Barnum was a wealthy entertainment producer with a reputation for outrageous marketing trickery. He was also, oddly enough, a skeptical activist, declaring, “I have devoted a portion of my life to the detection of humbugs.”1 He testified in court against mediumistic deception (see Part One of my two-part Junior Skeptic story on spirit photography, bound inside Skeptic Vol.19, No.2), offered James Randi-like cash challenges for proof of psychic ability, and in 1865 wrote a debunking book, Humbugs of the World.

Here is that book’s discussion of placebos in the context of “medical humbugs” (and also quackery, though here he’s poking more specifically at the opacity and paternalistic deception found at that time in mainstream medical practice):

One sort of regular-practice humbug is rendered necessary by the demands of the patients. This is giving good big doses of something with a horrid smell and taste. There are plenty of people who don’t believe the doctor does anything to earn his money, if he does not pour down some dirty brown or black stuff very nasty in flavor. … It is a milder form of this same method to give what the learned faculty term a placebo. This is a thing in the outward form of medicine, but quite harmless in itself. Such is a bread-pill, for instance; or a draught of colored water, with a little disagreeable taste in it. These will often keep the patient’s imagination headed in the right direction, while good old Dame Nature is quietly mending up the damages in “the soul’s dark cottage.”2

To Look Is to See

My 2013 book with INSIGHT’s own Don Prothero on the topic of cryptozoology, Abominable Science!, emphasizes that many cryptid sightings are “mistakes generated by expectant attention.3 When people visit the shores of Loch Ness, for example, it’s difficult for them not to have their senses primed at least a little bit for signs of a monster. The combination of focus and tension is a recipe for false positive sightings. (Such priming was, for example, clearly a factor in the multiple mistaken monster sightings made by Nessie investigator Tim Dinsdale during his first few days at the Loch.)4

The influence of expectation upon perception has long been discussed in the skeptical literature—for good reason.

“Everywhere we are apt to perceive what we expect to perceive, in the perception of which we have an interest.”

Early 20th century psychologist Joseph Jastrow was a giant in his field who has been described as “America’s first pop psychologist.” He was also a long-time skeptical activist who corresponded and collaborated with other skeptics, and wrote several books seeking to shed light on fringe topics and promote critical thinking, including Fact and Fable in Psychology (1900), Effective Thinking (1931), and Wish and Wisdom: Episodes in the Vagaries of Belief (1935). In his 1900 discussion of ways in which subjective factors can influence our perceptions, especially when an observation is “made under poor conditions,” Jastrow emphasized:

Expectation, or expectant attention, is doubtless the most influential of all such factors. When awaiting a friend, any indistinct noise is readily converted into the rumbling of carriage wheels; the mother hears in every sound the cry of her sick child. … Everywhere we are apt to perceive what we expect to perceive, in the perception of which we have an interest. The process that we term “sensation,” the gathering of evidence by the senses, is dual in character, and depends upon the eyes that see as well as upon the things that are present to be seen.5

Involuntary Motion

Ouija boards, pendulum divining, and dowsing for water are all so tremendously old that their origins are “lost in antiquity” (as one lengthy skeptical review of the dowsing literature review put it in 19386). There were, for example, ouija boards in use in the 4th century Roman Empire.7 By the first half of the 19th century it was clear that many such phenomena depend, as Joseph Jastrow later summarized, upon “involuntary movements under expectant attention.”8

A pioneer in this understanding was French chemist Michel-Eugène Chevreul, who for his own satisfaction conducted systematic tests using a dowsing pendulum in 1812. In 1833, at the request of André-Marie Ampère, he finally put his observations and conclusions into print. He found that the pendulum did indeed swing in apparent response to various substances, as proponents said it should, and that the oscillations dampened when a piece of glass or other obstacle was interposed between the pendulum and the test substance. But when Chevreul tried the tests again with various braces to prevent involuntary movement, the “the pendulum’s movement decreased progressively as the support was coming closer to my hand, and that it ceased when the fingers that were holding the thread were themselves braced….” This was a critical discovery:

That caused me to think that quite probably a muscular movement that was taking place unbeknownst to me was determining the phenomenon…thus I thought that if I were to repeat the experiment with a blindfold on, the results might be quite different from those I had observed. That is precisely what happened.9

It turned out that the pendulum could only “react” to test substances that Chevreul could see. The device’s mysterious action required both freedom for subtle involuntary movements and visual cues to trigger and direct the oscillations. Armed with this understanding, Chevreul went on to head a commission on the topic of pendulum dowsing in 1853, published (in French) as a book in 1854.

Today, skeptics refer to the involuntary action of the dowsing rod, facillitated communication techniques and similar phenomena as the ideomotor effect. Perhaps surprisingly, that term is almost as old as the understanding that the effect exists. It was coined in 1852 by English physician, zoologist, and skeptic William Benjamin Carpenter:

Thus the ideo-motor principle of action finds its appropriate place in the psychological scale, which would, indeed, be incomplete without it. And, when it is once recognized, it may be applied to the explanation of numerous phenomena which have been a source perplexity to many who have been convinced of their genuineness, and who could not see any mode of reconciling them with the known laws of nervous action. The phenomena in question are those which have been recently set down to the action of an “Od-force,” such, for example, as the movements of the ‘divining rod,’ and the vibration of bodies suspended from the finger; both of which have been clearly proved to depend on the state of expectant attention on the part of the performer, his Will being temporarily withdrawn from control over his muscles by the state of abstraction to which his mind is given up, and the anticipation of a given result being the stimulus which directly and involuntarily prompts the muscular movements that produce it.10

Elephants In the Room

In 1999, psychologists Christopher Chabris and Daniel Simons conducted a simple little psychology experiment which, to their surprise, became one of the most famous experiments of recent decades. They asked Harvard undergraduates to view a short video while completing a seemingly simple counting task—counting passes between basketball players—with shocking results. If you are not already familiar with this experiment, I strongly encourage you to try it yourself, now, before reading any further. Keeping count accurately is trickier than it sounds, so watch carefully! Here’s the video:

Did you see it?

Roughly half of those who try this experiment for the first time do not. I was among those who were shocked almost to disbelief when the video was replayed to reveal the punchline. “How could I have overlooked something so obvious? I mean, really—how is that even possible? Is that even the same tape?”

It is the same tape. Since 1999, many variations of this experiment have been tried, always with the same general result: roughly half the subjects fail to see the gorilla, or odd red shape, or whatever similar unexpected thing the experimenters inject into some given focus-demanding task. This phenomenon has come to be known as “inattentional blindness“—the failure to perceive unexpected but obvious objects within one’s field of vision when one’s attention is otherwise engaged.11

Moreover, there seems to be no difference of personality or ability which predicts who will notice and who won’t. “As far as we can tell,” Chabris and Simons concluded after experimentally probing several plausible differences, “there are no such people as ‘noticers’ and ‘missers’—at least, no people who consistently notice or consistently miss unexpected events in a variety of contexts and situations.”12 Human beings just aren’t very good at the cognitive equivalent of chewing gum and walking at the same time. When we’re paying attention to one thing, we are by definition not paying attention to everything else. This has serious implications for routine multitasking, of course, with the dangers of driving while talking on the phone (hands free or not) being a well-known example.

You will not be surprised to hear that the limits of focus and its implications for intentional deception and paranormal experience long ago came to the attention of skeptics. In his 1907 exposé Behind the Scenes With the Mediums, David Phelps Abbott (an influential amateur magician who performed primarily for professional magicians, and who invented the basis of the obedient ball trick performed by magician Teller today) placed this phenomenon into paranormal context:

A magician once remarked to me, “If I can only get your attention intently, an elephant can pass behind me and you will not see it.” This may have been a little strong, but not so much so as one who is not himself a performer might suppose. The attention is like the field of vision—it can only be concentrated on one thing at a time.

If any one reports a slate-writing, where he took his own slates, did not let them go out of his hands, and allowed no one to touch them in any manner, he is surely mistaken if truthful. There has been something which occurred, and which he does not relate, for the simple fact that it escaped his attention at the time—something that to him seemed a mere incident, a little thing, an accident, or that he did not perceive at all; but that was really the vital point, as it concealed the trick. This is the verdict of all the reliable conjurers who have ever investigated the subject.13

Joseph Jastrow emphasized this same relationship between focused attention and blindness to unrelated stimuli—and resulting vulnerability to deception—in 1900, saying,

A call upon the attention in one direction prevents its dispersion in another. When engrossed in work, we are oblivious to the noise of the street or even to the knock at the door. An absent-minded person is one so entirely “present-minded” to one train of thought that other stimuli go unperceived. The pickpocket is psychologist enough to know that at the railway station, the theatre, or wherever one’s attention is sharply focused in one direction, is he apt to find the psychological moment for the exercise of his pursuit. It is in the negative field of attention that deception effects its purpose.14

Looking Forward, Looking Back

I spend quite a lot of time looking at skeptical history—enough to feel daunted by it. There’s just so much to learn about the skeptics whom skeptics have forgotten. The few psychological principles mentioned in this post are just the tiniest keyhole view into the skeptical work of previous generations. But there’s much to feel inspired by in the rediscovery of that work.

I turn to the labors of the year ahead with a sense of fraternity with those long-ago men and women who strove to understand the fringe, curb its excesses, and tell the public what they had learned. Today, as we toil in that same obscure, fantastical field, we till the same soil and maintain the same fences. And, if we are wise, we harvest crops whose seeds were planted long before we were born.

Happy New Year, skepticism.

  1. From “Spiritualism in Court. The Mumler Examination Continued—P.T. Barnum, Esq., On the Stand.” New York Daily Tribune. April 29, 1869, p. 2, as reprinted in Louis Kaplan. The Strange Case of William Mumler, Spirit Photographer. (Minneapolis: University of Minnesota Press, 2008.) pp. 194–197
  2. P.T. Barnum. Humbugs of the World. (London: John Camden Hotten, 1866.) p.173. Available free in a variety of digital formats at the Internet Archive.
  3. Daniel Loxton and Donald Prothero. Abominable Science! Origins of the Yeti, Nessie, and Other Famous Cryptids. (New York: Columbia University Press, 2013.) p. 133
  4. Ibid. pp. 151–152
  5. Joseph Jastrow. Fact and Fable in Psychology. (New York: Houghton Mifflin Company, 1900). pp. 120
  6. Arthur J. Ellis. The Divining Rod: a History of Water Witching. (Washington: Government Printing House, 1938.) p. 8
  7. Ammianus Marcellinus. (C.D. Yonge, trans.) The Roman History of Ammianus Marcellinus. (London: G. Bell and Sons, 1911.) pp. 510–511, as transcribed online at For discussion by previous generations of skeptical authors, see for example Joseph Jastrow. Error and Eccentricity in Human Belief. (Dover Publications: New York, 1962.) pp. 128–129; and, Andrew Lang. Cock Lane and Common-Sense. (London: Longmans, Green, and Co., 1894.) pp. 315–316. Available free in various digital formats at the Internet Archive.
  8. Jastrow, Joseph. Error and Eccentricity in Human Belief. (Dover Publications: New York, 1962.) p. 128–131
  9. Herman H. Spitz and Yves Marcuard. “Chevreul’s Report on the Mysterious Oscillations of the Hand-Held Pendulum: A French Chemist’s 1833 Open Letter to Ampere.” Skeptical Inquirer, Vol. 25, No. 4, July/August 2001. pp. 35–39. Includes complete translation of Chevreul’s 1833 paper, plus commentary.
  10. Carpenter, William. “On the Influence of Suggestion in Modifying and directing Muscular Movement, independently of volition.” Notices of the Meetings of the Royal Institution. 1852. p. 147. As reproduced at
  11. Christopher Chabris and Daniel Simons. The Invisible Gorilla. (New York: Broadway Paperbacks, [c.2011]) pp. 6–7
  12. Ibid. p. 32
  13. David Phelps Abbott. Behind the Scenes with the Mediums. (Chicago: The Open Court Publishing Co., 1907.) pp. 115–116. Available free in various digital formats at the Internet Archive.
  14. Jastrow (1900). pp. 120–121
Daniel Loxton

Daniel Loxton is the Editor of INSIGHT at and of Junior Skeptic, the 10-page kids’ science section bound within Skeptic magazine. Daniel has been an avid follower of the paranormal literature since childhood, and of the skeptical literature since his youth. He is also an award-winning author. Read Daniel’s full bio or his other posts on this blog.

1 Comment
Inline Feedbacks
View all comments

Get eSkeptic

Be in the know!

Subscribe to eSkeptic: our free email newsletter and get great podcasts, videos, reviews and articles from Skeptic magazine, announcements, and more in your inbox twice a week. It’s free. We never share your address. Unsubscribe any time.

Sign me up!


Skeptic cover art by Pat Linse

Art of the Skeptic

In celebration of Skeptic magazine’s 100th issue, we present sage graphic art advice for skeptical groups and a gallery of art reflecting more than 47 years of skeptical activism from Skeptic’s long time Art Director, Pat Linse

Detecting Baloney

Baloney Detection Kit Sandwich (Infographic) by Deanna and Skylar (High Tech High Media Arts, San Diego, CA)

The Baloney Detection Kit Sandwich (Infographic)

For a class project, a pair of 11th grade physics students created the infographic shown below, inspired by Michael Shermer’s Baloney Detection Kit: a 16-page booklet designed to hone your critical thinking skills.

FREE PDF Download

Wisdom of Harriet Hall

Top 10 Things to Know About Alternative Medicine

Harriet Hall M.D. discusses: alternative versus conventional medicine, flu fear mongering, chiropractic, vaccines and autism, placebo effect, diet, homeopathy, acupuncture, “natural remedies,” and detoxification.

FREE Video Series

Science Based Medicine vs. Alternative Medicine

Science Based Medicine vs. Alternative Medicine

Understanding the difference could save your life! In this superb 10-part video lecture series, Harriet Hall M.D., contrasts science-based medicine with so-called “complementary and alternative” methods.

FREE PDF Download

Top 10 Myths of Terrorism

Is Terrorism an Existential Threat?

This free booklet reveals 10 myths that explain why terrorism is not a threat to our way of life or our survival.

FREE PDF Download

The Top 10 Weirdest Things

The Top Ten Strangest Beliefs

Michael Shermer has compiled a list of the top 10 strangest beliefs that he has encountered in his quarter century as a professional skeptic.

FREE PDF Download

Reality Check: How Science Deniers Threaten Our Future (paperback cover)

Who believes them? Why? How can you tell if they’re true?

What is a conspiracy theory, why do people believe in them, and can you tell the difference between a true conspiracy and a false one?

FREE PDF Download

The Science Behind Why People See Ghosts

The Science Behind Why People See Ghosts

Mind altering experiences are one of the foundations of widespread belief in the paranormal. But as skeptics are well aware, accepting them as reality can be dangerous…

FREE PDF Download

Top 10 Myths About Evolution

Top 10 Myths About Evolution (and how we know it really happened)

If humans came from apes, why aren’t apes evolving into humans? Find out in this pamphlet!

FREE PDF Download

Learn to be a Psychic in 10 Easy Lessons

Learn to do Psychic “Cold Reading” in 10
Easy Lessons

Psychic readings and fortunetelling are an ancient art — a combination of acting and psychological manipulation.

FREE PDF Download

The Yeti or Abominable Snowman

5 Cryptid Cards

Download and print 5 Cryptid Cards created by Junior Skeptic Editor Daniel Loxton. Creatures include: The Yeti, Griffin, Sasquatch/Bigfoot, Loch Ness Monster, and the Cadborosaurus.

Copyright © 1992–2021. All rights reserved. | P.O. Box 338 | Altadena, CA, 91001 | 1-626-794-3119. The Skeptics Society is a non-profit, member-supported 501(c)(3) organization (ID # 95-4550781) whose mission is to promote science & reason. As an Amazon Associate, we earn from qualifying purchases. Privacy Policy.