Posted: Dec 19, 2010 8:06 pm
by natselrox
Canon in S(cience)

Debunking Common Sense Psychology

Canon (music): In music, a canon is a contrapuntal composition that employs a melody with one or more imitations of the melody played after a given duration (e.g. quarter rest, one measure, etc.). The initial melody is called the leader (or dux), while the imitative melody, which is played in a different voice, is called the follower (or comes). The follower must imitate the leader, either as an exact replication of its rhythms and intervals or some transformation thereof.[1]


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Christmas time! You’re walking through the busiest street in town. Everyone’s out shopping. You jostle past moving blobs of wool and fur, dodge those pesky little kids and suddenly you see Mr. Jones in the cake shop, bargaining as usual. Cheeky old bugger! But he’s a nice man. Everything is normal, festive, and fine. Now stop for a moment. Think of what you were doing. “I was walking on the street, you dumbo!” Of course you were. But try and describe every action of yours in detail. You were seamlessly moving past obstacles without even paying conscious attention to them. You recognised Mr. Jones at the slightest glance through the corner of your eyes, although chances are slim that you had seen him previously in the same pose from exactly the same distance and angle.[2] Common sense tells us everything was normal and as they should have been. Science will help us to frame the right questions and see the extraordinary. Shall we search for the devil in the details?

You enter a toy-shop to buy a present for your nephew. You don’t exactly what kids like these days. Uno, Pokemon, Dinosaur models, books of stars... hmm... You are confused. You try to project your youth onto the frame of your nephew but you’re not entirely convinced. After all, you’ve seen him jumping up and down in his room with his Wii. You look around the shop. People are busy looking at different items. About 25 people are there in the shop. Are they all buying presents for Christmas? Maybe someone is buying a present for their child’s birthday. Maybe more than one of them are buying presents for their child’s birthday. Maybe their children share the same birthday. But what are the odds of that happening? Pretty slim, it seems. Forget it! So finally, you decide to pick a telescope for kids. Maybe he will show interest in Astronomy. Let’s buy the DVD box set of Cosmos with it as well! After you’re done with the billing and gift-wrapping, the girl at the counter tells that they have a little game for you. She shows you three boxes and tells that one of them has a present in it and the others are empty. You have to pick one. But here’s the catch. After you’ve picked one box, she is going to show an empty box from the remaining two and then you get the chance to switch to the remaining box or stick with your choice. What should you do? Common sense tells us, we either picked the prize-box or we didn’t. What difference does it make to switch? Guess what, your common sense has dumped you again. You will be wrong to not switch the box and you were wrong in the assumption about the chances of a birthday-coincidence. Once again, science will help us out.

You return home. But you can’t resist the temptation to open the packaging of the telescope and try it out once for yourself. Besides, you need to check if it’s working as well. It’s a clear starry night. As you set the telescope in your balcony, you hear the faint tunes of ‘Lucy in the Sky’ playing from a distant house. How you love the Christmas time! The starlight is coming from light-years away. Some of the stars are like our sun, some are a lot bigger, some are much younger, and some are approaching senescence. Carl Sagan’s voice resonates with the ambience; you are standing on a mote of dust trying to comprehend the nature and purpose of the universe. The astronomical dimensions seem incomprehensible. The age of stars, the age of life on earth are just numbers to us, intangible. It does not mean anything to say that the values of the observable are the eigenvalues of Hermitian operators of vectors. But it’s the only way we can represent reality. The world, as we see it, is incredibly complex and almost impenetrable to our common sense wisdom. As you stand contemplating these things, you suddenly realise that it’s Isaac Newton’s birthday. He once said, “If I have seen further it is only by standing on the shoulders of giants.” Indeed, science augments our ability to understand the universe by rendering our normative, interpretive and teleological common sense redundant.

We are primarily visual animals. In fact, as Richard Gregory pointed out, “We are so familiar with seeing that takes a leap of imagination to see that there are problems to be solved.”[3] Our intuition tells us that our eyes are like cameras, passively mapping the external world onto the retina and subsequently, the brain. This model of one-to-one mapping was the prevalent view for most part of history. In fact, the whole process of perception was thought of as a simple process of assembling elementary sensations in an additive way, component by component, till the eighteenth century and was endorsed by the likes of John Locke and George Berkeley. The balance tilted towards the creative model of perception from a passive phenomenon through the rise of Gestalt psychology in the early twentieth century by the German psychologists (Max Wertheimer, Kurt Koffka, and Wolfgang Kohler).[4] The best way to try and appreciate the creative aspects of visual processing is through illusions.


In the above image, the top picture presents an ambiguous pattern. In the left-hand column, dots of the same colour are grouped together in rows/columns which causes the brain to see rows and columns. What's more interesting is that in the right hand column, the perception of the dots being arranged in rows and columns is being created merely by their proximity with the corresponding elements of the left-hand column.


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Whenever we see something, some parts of the imagery is recognised as the object while the rest is relegated to background. This is famously illustrated by the Rubin's vase[6] where the viewer switches between seeing two faces and a vase. But the most famous works in figure-ground reversal was probably done by the Danish artist Maurits Escher who wrote, "Our eyes are accustomed to fixing on specific objects. The moment this happens everything around is reduced to background.… The human eye and mind cannot be busy with two things at the same moment, so there must be a quick and continual jumping from one side to the other."[5]The Kanizsa triangle illustrates how the brain fills in the triangle when actually none exist. In fact, as proposed by Koch and Crick, the illusory edges of the triangle are neurally represented in the same way as the real edges of a normal triangle.[7] The Müller-Lyer illusion shows how we use shape as an indicator of size and infer that the lines are unequal when in fact they are of the same length.[8]

In case of afterimages, we see an image after the cessation of the original stimulus[9]. In a somewhat opposite case, motion induced blindness makes the visible invisible by masking it with overlapping sensations[10]. A more dramatic example of this is flash suppression where an angry face is projected onto one eye and a random mosaic is projected onto the other eye. An observer with both the eyes open cannot see the angry face but shows fear responses in the brain. The angry face somehow fails to reach the brain pathways responsible for conscious perception.[11]

I mentioned a few illusions just to illustrate the idea that visual perception is a complex process involving both bottoms-up and top-down processing and involving multiple parallel pathways (conscious or otherwise) which 'bind' together to give rise to what we call 'vision'.[12] Or as Henry David Thoreau said, "The question is not what you look at, but what you see."

What about the box in the shop? Why was it better to have switched your original one? Let's see. So there are two possible scenarios in the beginning. Either you could have picked the box with the prize or an empty one. Had you picked the right box, you would be at a loss in switching. However, if you had picked an empty box, then after she showed the other empty box, you would have won the prize if you switched. Now, the second scenario is more likely than the first simply because, initially, there were two empty boxes compared to the one lucky box. Common sense, as we know it, would have significantly reduced your chances of winning the prize. [13]

Now to the birthday problem, what are the odds of there being a shared birthday among the twenty five persons present in the shop? What we have to understand is that, twenty five people means there are 300 pairs of birthdays between them and what you are actually doing is taking 300 pairs of birthdays and seeing if any one of them match or not. Now the odds do not seem so unlikely. In fact, a little maths will show that with only 23 people in a room, it is more likely than not that someone will share his/her birthday with another person in the room. Seems counterintuitive? Work it out for yourself! [14]

Now to the comprehension of astronomical dimensions, geological time and the weird nature of the physical sciences. You see, the caveman staring at the night sky would have had no way of guessing that the tiny little specks of light in the sky are in fact, giant balls of fire like the sun. It took us centuries of research and experimentation to frame a model of the universe that is getting closer to the the observed reality day by day. In the way we have rejected millions of hypotheses and are left with something that is weird, that is incompatible with our common sense and perhaps, in the words of Haldane, 'queerer than we can suppose'. Tiny mutations chiseling self-replicating molecules over billions of years can create sentient beings. We cannot envisage this yet all the evidence point to it. Relativity is nothing like anything but it explains what we see. Trying to make it simpler by dumbing down will not preserve it. Einstein said,"Make things as simple as possible, but not simpler." Quantum Mechanics is absurd but it is the closest that we have ever been to the truth. Common sense is not science. In fact, one of the purposes of science is to help us see through the veil of common sense.

As shown by the optical illusions, naive realism is what it is called, naive. Our behaviours are the result of chiseling by learning through experience on a broad, plastic canvas shaped by evolution. So our sensory inputs are highly processed and programmed to confer some sort of evolutionary and/or adaptive advantage needed for survival. Even if they don't, they have no obligation to conform to the reality. We need an objective mechanism to probe into the nature of reality, to unweave the fabric which nature uses to weave her tapestry. Clearly, our senses are not equipped to do that.

We are piss poor at calculating probabilities of events as has been documented by our reliance on the supernatural. Being unable to deduce the actual figures, we often ascribe natural phenomena to the supernatural. Our propensity to see miracles in ordinary events, the prevalence of superstitions across cultures, all stem from our lack of understanding. In our arrogant ignorance, we feel proud to be inhabiting this tiny little planet in this vast universe and assume that we have a special position.

In fact, if we can and shed these primitive notions of ours and adopt a scientific viewpoint, we'll see that the world as we saw it thorugh our common sense psychology is nowhere close to the reality. Only through the scientific method can we devise a meaningful model of the universe that has any resemblance to the truth.

I started with a Christmas theme. Having grown up in India, I'm not at all familiar with the Christmas spirit of the predominantly-Christian nations in the northern hemisphere. It sounds nonsense, but if I were to make a wish for Christmas, I'd say that I hope for a world where every child would get the opportunity to see the world through a scientific lens free of dogma. Trust me, it's much more beautiful that way.

Merry Christmas!

Further Reading:

[1] Taken from Pachelbel and Douglas Hofstadter somehow had sex in my mind to give birth to the idea of framing this essay loosely on the style of a canon. :shifty:

[2] Face recognition is a highly evolved mechanism in humans with different circuits responding to various faces and this can be probed by electrodes. In fact, a series of wonderful experiments are being done by Koch and his team, one of which (The Marilyn Monroe Neuron) was wonderfully covered by Carl Zimmer here. In monkeys, Inferotemporal lobe neurons responding to specific angles of viewing of the face have also been identified (by D. Sheinberg and N. Logothetis). It is kind of dumbing down to say that there are specific neurons for these purposes. When I asked Mo Costandi about these, he replied, "Each cell is a node in a sparsely distributed network encoding memories of Marilyn Monroe. It likely responds to other stimuli under different circumstances. Overlapping distributed networks; no grandmother (or MM) cell." However the full discussion is beyond the scope here. However, we can appreciate the difficulty in identifying a face under almost infinitely different circumstances. This is painfully manifested in patients with prosopagnosia. For a touching account, read the case of Dr. P in Oliver Sacks' "The Man Who Mistook His Wife for a Hat".

[3] Richard L. Gregory; Eye and Brain ; 1966

[4] I got these primers about the origins of these schools of psychology from Kandel and Schwartz. But a better place to look at would be the Wikipedia page ( and the links therein.

[5] Maurits Escher's paintings are works of pure genius. Do check them out! :cheers:


[7] Francis Crick and Christof Koch proposed the activity principle which states that underlying every direct and conscious perception is an explicit representation whose neurons fire in some special manner. So, for the illusory edges of the triangle, there will be one or more groups of neurons explicitly representing the different aspects of this percept.



[10] Motion Induced Blindness is a wonderful gateway to the neural correlates of visual consciousness. These are loaded terms and are beyond the scope of discussion here. But I'll tell you to look at this video to get an idea of how we are using these glitches in the matrix to try and understand its inner workings. :grin:

[11] Read Koch's article in the Scientific American for a brief description of this wonderful experiment. Especially read the part where you'll be sexually stimulated in a Freud-esque way. ;)

[12] The binding problem has somewhat lost its glamour over the years but it still remains a favourite among certain school of philosophers (or at least one that I know) :P .

[13] The wikipedia article on the Monty Hall Problem is near perfect!

[14] For a lively discussion on Probability, Randomness and the Birthday Paradox, listen to the BBC Podcast here. Beware though, it features Brian Cox, Tim Minchin and Alex Bellos! :grin: