The Role of Perception in Science: Part 1 “Correlation vs. Causation”

A few years ago I recall waking up thirsty and getting up to go get a drink of water. Inching my way through the dark I remember seeing my cat sitting patiently at the front door. I reached down to pet her speaking the affectionate words, “Who’s a kitty? Who’s a kitty?” A couple unrequited pets later I realized I wasn’t petting a cat at all; I was actually petting my oldest son’s felt-lined Sorel winter boots. Feeling a little silly I chuckled to myself, got my drink, and returned to bed. I assume I’m not the only person who has made a mistake in perception like this. This is what I’d call an honest mistake. There are times, however, when our mistakes are less honest, more or less a result of human nature or our desire (for whatever reason) to believe in comforting falsehoods. For this reason the scientific method is an invaluable tool helping us reliably test claims made about the world. Yet, despite having this methodology available to us we continue, figuratively speaking, mistaking boots for cats.

We are natural born story tellers: historically speaking we’ve developed some interesting ways of interpreting what we see and experience. In 1700 BCE the Babylonians saw what they believed to be divine displeasure whenever eclipses occurred. For this reason Babylonian priests conducted elaborate rituals to appease gods like Tiamat and Abzu. Siberian peoples, like the Chukchee, believed they could stop strong winds by simply dropping their pants, bending over and chanting, “Western Wind, look here! Look down on my buttocks. We will give you some fat. Cease blowing!” More recently, in 2012 to be exact, a crucifix in Mumbai, India, was discovered to be “crying.” Hundreds of thousands of eager Catholics have since visited the site in order to drink the “tears” hoping to either be healed or to get a glimpse of the divine.

Eclipses end and unruly winds cease. But not because of elaborate ceremonies or ritual flashing. In the case of either the ancient Babylonians or contemporary Indian Catholics, both confused correlation with causation. An honest mistake, really. Philosopher David Hume (1711-1776 AD) described the problem with our penchant for story telling in the following way: someone sees Y happen after they see or perform action X; that same someone then concludes X is the cause of Y while predicting the pattern will hold true for the future. This X causes Y business looks a lot like reasoning; however, the whole process has more to do with Pavlovian conditioning than thinking as defined.

Hume was essentially arguing that through errors in perception we create correlations between any two or more things.


For example, let’s correlate rising sea levels with one or more of the following:

  • Rising Somali piracy off the coast of East Africa
  • Justifiable declining sales of Justin Bieber albums
  • Increasing likes on any given cat video found on YouTube
  • The political fortunes of the Muslim Brotherhood in Egypt
  • The prospects for democracy in Russia

You get the point: any two things—no matter how obscure or disconnected—can exist in a perceived relationship or correlation. For this reason David Hume warned, “When men are most sure and arrogant they are commonly most mistaken, giving views to passion without that proper deliberation which alone can secure them from the grossest absurdities.” Hume cautioned us from assuming we could know something so well, so certainly, no further work or understanding was required of us. Hume’s biographer, Roderick Graham, added that although Hume supported the cause of reason the philosopher nonetheless felt relying on it alone led to intellectual complacency and blindness. Something was needed to prevent people from using reason simply to invent reality or fall back relying on old certainties. Hume felt the only means available to us to minimize error was the use of the scientific method.

Scientists establish cause and effect by proving that effects observed in an experiment proceed from an identifiable cause. This appears to be something relatively easy to accomplish; nonetheless, the world is a complicated place and doesn’t necessarily submit to our need for clear cut explanations. There’s rarely ever one variable to consider when studying any phenomenon. So we need to be disciplined when inducing Nature to give up her secrets and we do this through a process called falsification, e.g. ask a question, construct an experiment to test the question, and then either falsify (disprove) or confirm the question’s claim. If we confirm the question’s claim, then we pass on what we’ve learned to the scientific community for replication; if the results are successfully repeated multiple times (ideally by different groups) we might be able to tease out a cause and effect relationship.

To their credit the Babylonians eventually worked it out for themselves eclipses faded away all on their own. I’m not so sure if the Chukchee worked it out with the wind. I can say, however, with virtually 100% certainty (and I say virtually because there’s no such thing as 100% certainty in science) buttocks slapping likely has no influence over prevailing weather patterns. Further still, the crying crucifix in Mumbai turned out to be not so sad after all—the “tears” were the product of a leaking toilet and clogged drain in an adjacent room. A science-minded chap named Sanal Edamaruku had the audacity of appealing to known physics—the capillary action of water specifically—rather than a miracle for an explanation.


The capillary action of water is defined as water’s capacity to adhere to the walls of a container causing an upward force on the liquid forcing the water upward. Yes, water can flow up a wall. In the case of the statue, a clogged drain in the adjacent bathroom contributed to water spilling on the floor, permeating the wall, climbing said wall, soaking through the other side, finally dripping on to the crucifix in the adjacent room, eventually forming in to a pool at the foot of the statue. The Catholic Church in India subsequently brought charges of blasphemy against Edamaruku. Apparently blasphemy is still a “thing” in the 21st century. Edamaruku fled to Finland to avoid prosecution. The funny thing is the hypothesis that the crucifix was crying was entirely falsifiable, i.e. fix the toilet and unclog the drain and see whether or not water still collects on the statue. Regrettably, you can take the person out of the 10th century but it’s an entirely different thing taking the 10th century out of the person…

A number of years ago I came across a story, more than likely fictitious, of a professor of anatomy who discovered the body he was dissecting didn’t look at all like the diagram in Galen’s On Anatomical Procedures. Galen (130-200 AD) was a Greek anatomist who had the misfortune of working at a time when the Catholic Church outlawed the dissection of human corpses. Ultimately, Galen was forced to rely on dissecting pigs and apes to develop his ideas on human anatomy. For this reason people prescribed to the Genesis­-based idea that men had one less rib than women; that is, until Andreas Vesalius (1514-1564 AD) falsified the “rib hypothesis” by actually looking to see if there was a difference between men and women. We have the exact same number of ribs. Thomas Paine (1737-1809 AD), author of The Age of Reason, explained the reason people believed in falsehoods was because of “the long habit of believing a thing true [giving] it the superficial appearance of being right.” For this reason a certain professor of anatomy ignored the need to conduct tests, like so many of us do, by succumbing to arguments from authority and tradition.

Another professor, an Italian named Galileo Galilei (1564-1642 AD), was less inclined to accept arguments from authority. In the mid-1600s, and thanks to the Greek philosopher Aristotle (384-322 BCE), people believed the commonsensical notion larger objects fell faster to the ground than smaller ones because of their relative mass. Galileo knew this description of gravity, an example of storytelling, was false and wanted to disprove Aristotle (no small feat considering people tend to get defensive and double-down to protect tradition). Therefore, Galileo designed a 50965500simple thought experiment to test Aristotle’s assertion. The experiment involved having students drop two objects (one large, one small) from the leaning tower at Pisa. There’s some debate as to whether the experiment actually took place; however, what is not debatable is had it taken place the objects would have hit the ground, as would have the jaws of Aristotle’s supporters, at precisely the same time. Aristotle was unseated and we knew just a little more about how the world actually worked; not because of butt-slapping or revelation or Church doctrine but because of the scientific method. What’s sad is four centuries later writers like myself are still trying to convince the public “science delivers the goods.”

To his credit Aristotle looked to natural causes instead of to gods to explain why the world worked as it did; however, Aristotle’s methodology was fundamentally flawed in at least two respects: firstly, he trusted too much in his own power of deduction to help him see how things worked, e.g. I don’t feel the earth moving therefore it must not be moving (a false deduction leading to a false correlation). (Actually, the earth is moving at 15 km/s around the Sun while rotating on its axis, moving up and down following the Sun’s 23 million year procession, wobbling at the impress/interplay of the Sun/Moon, tilting every so often. There’s no single static, immovable point or center in the universe either; everything is moving.) Secondly, unlike Galileo, Aristotle never conducted a single experiment. Not a one.

So what does all this mean for people living the 21st century? For one accept the possibility it might be wise to suspend your judgement until you have something concrete, something real supporting a particular claim or belief you hold. Secondly, common sense is a completely inadequate basis for forming trustworthy or informed opinions—for example the cause of homelessness is not usually a reflection of an individual’s laziness but frequently of their mental illness; the cause of criminality is not that people are bad but live in poverty and are forced to do things they wouldn’t do if their material circumstances improved; and a person’s sexual orientation isn’t a choice so much as a reflection of genetics. Thirdly, quit trusting in your gut so much: I recall reading about an interaction between a journalist and the astrophysicist, Carl Sagan (1934-1996 AD). The journalist asked the scientist about the possibility of life existing on other planets. Sagan hesitated to respond. When pressed to share his “gut feeling” Sagan responded, “But I try not to think with my gut. Really, it’s okay to reserve judgement until the evidence is in.” It’s okay to wait for evidence before making your mind up; it really is.

We would do well relying less on our gut or imagination so much—because guts tell us stories like ‘vaccines cause autism,’ ‘larger objects fall to the ground faster than small ones,’ ‘God puts fossils in the ground to test our faith,’ ‘the earth doesn’t move,’ or ‘trickle-down economics’ works as defined. Evidence based decision making means being willing to deal with the world as it actually is as opposed to how we would rather have it. This applies to every aspect of decision-making from science to politics and even to mistakenly petting Sorel boots.


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