Constructive Nature of Perception

David Kyle Johnson

I would like all people to know that I do believe that this is the Virgin Mary, Mother of God.

Diana Duyser, about a “face” in her grilled cheese sandwich

Many of the things that we believe are generated by our senses interacting with the outside world.

What does it mean for perception to be constructive? Take vision, for example. Our eyes do not just take a picture and then present the world to us as it is. They receive information about the world, send that information to our brain, and then our brain interprets that information in certain ways based on certain criteria. It decides what is relevant, disregards what is not, and then determines how that information should be presented to us.

In many cases, that presentation is inaccurate. As Yale neuroscientist Steven Novella (2016) once put it:

[Our] brains construct [our] image of reality [...] we are not passive recorders of reality. What you experience as your stream of consciousness is an incredi­bly highly filtered, and selected and altered and reconstructed narrative of what’s going on. [.. It’s] very useful, but largely a fiction [because] in general your brain errs massively on the side of continuity and internal consistency [.] not accuracy.

The easiest example is simple: we perceive all objects in the world as solid despite the fact that they are mostly empty space. That’s simply how our brain interprets our sense data (see Matthews 2009). More interesting still, we perceive objects as having color when in fact they have no color at all. They merely reflect wavelengths of light that cause us to see certain colors (see Marder 2015).

This is why “dressgate” was so distressing to people. People fallaciously concluded that the dress must be the color they saw it as (and thus others who disagreed where crazy) because they didn’t realize that perception is constructive; they thought there is an objective fact about whether the dress is blue and black, or white and gold, when in fact the dress has no color at all - color is only in the mind (see Johnson 2015). The way you see the world is not necessarily the same as other people see it.

Our brains make decisions about what information to interpret and how to do so mostly based on our assumptions, preconceptions, and desires - our “worldview” if you will. We can see extreme (and interesting) cases of how this can lead us astray in brain-damaged patients. In “The Sound of One Hand Clapping” - one of my favorite chapters in V.S. Ramachandran’s book Phantoms in the Brain (1999) - Ramachandran tells the story of patients who have had strokes in their right hemisphere but consistently deny the fact that their stroke paralyzed the entire left side of their body. The denial is so strong that when asked to do tasks that require both hands, like tying their shoes, they will try to do them - they’ll fiddle at their shoe­laces with their right hand (left hand dangling at their side) - and then (incorrectly) insist they completed the task successfully “with both hands.” When asked to clap, they will raise only their right hand to the middle of their body, but insist that their left hand is raised too.

Ramachandran suggests this is because the stroke has inhibited their abil­ity to deal with information that conflicts with their worldview and corre­spondingly update it. Since their worldview before the stroke included the assumption that their left side was functioning, that’s the worldview they are stuck with after the stroke. And since our beliefs largely determine how we perceive the world, these patients literally perceive their arm moving when it is not.

We “normal” (non-brain-damaged) people can be subject to such things as well. Oliver Sacks, in his book Hallucinations (2012), goes into detail about how and why even normal people can suffer from hallucinations. You can probably even think of a few examples from your own personal life. I’ve seen my dog running in the kitchen when he’s not (he’s actually asleep upstairs). While I have been in the shower, I’ve heard the phone ring when it’s not. I have felt my phone vibrating in my pocket when it’s not; it’s not even in my pocket! This is because of the role of expectation in perceptual construction. According to Schick and Vaughn (2014, 101), by simply alter­ing what people expect, studies have shown that you can make people see lights flash, feel electric shocks or warmth, or even smell certain odors all without any of those things actually being present.

This is why, if you really want to know whether a house is haunted, you shouldn’t have someone tell you what the ghost is supposedly like or sup­posedly does. If you are expecting a certain thing to happen in a certain location in the house, you will probably experience it - especially if you go in already believing the ghost is real. This is also why ghost hunters always fail to find ghosts when they haven’t been told beforehand what to look for (see Grant 2005).

Another assumption that informs how we interpret the information that our brain receives is that the size, color, and shape of objects is constant.

Obviously this kind of perceptual constancy (as it’s called) can help us understand the world accurately - because usually objects aren’t chang­ing size, color, or shape. But it can also lead us astray. There are of course countless visual illusions that demonstrate this fact; one of my favorites is the checkerboard shadow illusion in which you will see two squares as completely different colors, when in fact they are the same (due to the way light and shadow affects our interpretation of visual information). But you can also demonstrate this experimentally. In one study, donkeys and trees were each cut out of the same green paper and illuminated with the same red light, yet the subjects still saw the donkey as grey and the tree as green.

Interestingly, however, much (if not all) of our perceptual constancy is learned. Being able to tell how large an object is even though it is far away (and thus appears small) is an acquired skill - one that you would not have if you had spent your entire life living in a thick forest or jungle where you never saw large objects from far away. Indeed, this skill of yours is only good for, at most, around a mile or two because you seldom have the chance to verify the size of objects further away than that. At a certain point, you have no idea whether you are looking at a distant larger object or a close smaller object, especially if that object is against a blank background like the sky.

This is why my friend, Tony, and I were once nearly convinced that a plane was going to slam right into a 7-foot delta kite we were flying in North Dakota one day. The kite was 1,000 feet up, and until the plane passed right over the kite (the plane was much higher), we had no frame of reference to judge the size or altitude of the plane.

Another reason people think they see UFOs (and another way our percep­tion leads us astray) is the autokinetic effect. If you stare at a stationary bright object against a solid background for a while, it will start to appear as if it is moving. It doesn’t actually take that long, and we don’t yet know for sure what causes this effect. (There are a couple of theories; see Rucci and Poletti 2009). But what we do know is that countless people have mis­taken the planet Venus for a UFO because of it.

This brings me to the last way our perception leads us astray that I’ll men­tion: pareidolia. One thing that our brain likes to do with the information it receives is impose patters on it. So when we, for example, see a vague amor­phous stimulus, we will often impose a pattern onto it and see something that is not actually there: a human face on mars, Jesus on a tortilla, the Virgin Mary on a grilled cheese, and so on. It’s often a face because of how much of our brain’s visual centers are dedicated to facial recognition, but it doesn’t have to be. I’ve also seen Godzilla in the clouds, a dog on a stained wall, and even the full body of an ascending Jesus in a dog’s butt (see Campbell 2013).

But vision is not the only sense susceptible to this effect. Our hearing is too. This is why you can sometimes hear “secret messages” in speech or music when you play it backwards.

Interestingly, however, you will almost never hear these secret messages unless you are told what words to listen for. When I play videos that have Beatles songs played backwards for my students and hide the subtitles, they can’t hear anything. But when I play the same thing with subtitles, they can’t hear anything else. This is why the TV series Ghost Hunters always put up subtitles when they play back the “voices” they mysteri­ously catch on tape; they are intentionally encouraging audio pareidolia. If they didn’t, you would just hear a garbled mess - because that is all there actually is.

All in all, our senses are not nearly as reliable as we think they are. As a result, we must guard against the many ways that they can lead us astray if we want to have any chance at understanding the way the world actually is. This is why science has proved to be such a powerful tool in understanding the world; it is designed specifically to guard against the way our senses (and also all the fallacies in this book) can lead us astray.

References

Campbell, Andy. 2013. “Dog Butt Looks Like Jesus Christ in a Robe.” TheHuffingtonPost.com, June 13. http://www.huffingtonpost.com/2013/06/13/ dog-butt-looks-like-jesus-photo_n_3436086.html (accessed October 3, 2017).

Grant, Eleanor. 2005. “Is It Real? Ghosts.” Is It Real? National Geographic, April 25. http://www.imdb.com/title/tt0861148/combined (accessed October 3, 2017).

Johnson, David Kyle. 2015. “The Blue/Black White/Gold Dress Controversy: No One Is Right.” Psychology Today, February 27. https://www.psychologytoday. com/blog/logical-take/201502/the-blueblack-whitegold-dress-controversy-no- one-is-right (accessed October 3, 2017).

Marder, Jenny. 2015. “That Dress Isn’t Blue or Gold Because Color Doesn’t Exist.” PBS Newshour, February 27. http://www.pbs.org/newshour/updates/that-dress- isnt-blue-or-gold-because-color-doesnt-exist/ (accessed October 3, 2017).

Matthews, Robert. 2009. “If Atoms Are mostly Empty Space, Why Is Matter not Transparent?” Science Focus, October 22. http://www.sciencefocus.com/qa/if- atoms-are-mostly-empty-space-why-matter-not-transparent (accessed October 3, 2017).

Novella, Steven. 2016. “Podcast #570.” The Skeptics Guide to the Universe, June 11. http://www.theskepticsguide.org/podcast/sgu/570 (accessed October 3, 2017).

Plait, Phil. 2010. “Why Does the Moon Look so Large on the Horizon?” Slate, May 13. http://www.slate.com/blogs/bad_astronomy/2010/05/13/why_does_the_moon_ look_so_huge_on_the_horizon.html (accessed 14 October 2017).

Ramachandran, V.S. 1999. Phantoms in the Brain: Probing the Mysteries of the Human Mind. New York, NY: Harper Collins.

Rucci, Michele, and Martina Poletti. 2009. “Fixational Eye Movements and the Autokinetic Illusion.” Journal of Vision 9(8): 431.

Sacks, Oliver. 2012. Hallucinations. New York, NY: Vintage Books.

Schick, Theodore, and Lewis Vaughn. 2014. How to Think About Weird Things: Critical Thinking for a New Age. New York, NY: McGraw-Hill.