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Sunday, May 31, 2009

Fact Checking is Important

Today I leave for Germany, so I am up early doing some last minute things. While eating breakfast and drinking tea, I was watching the news and saw Republican minority leader Mitch McConnell being interviewed. During the course of the interview, the intervewer presented Mr. McConnell with some statistics displaying massive support for a government health plan. Mr. McConnel responded first with, "Well, it's how you phrased the question. Had you phrased it, 'Do you want the government between you and your doctor?', you would have had much worse support." Of course, McConnell is conveniently leaving out the fact that currently it is the insurance company between you and your doctor, and the insurance company has far more incentive to deny health-care than the government. Anyway, what followed was worse, however. In trying to explain his boneheaded rephrasing of the question, McConnell said something along the lines of, "Because that what it will be. We see in countries that have national health plans long waits and delays in treatment, and that is reflected in their life spans."

When you are going to make a statement like that, know what the hell you are talking about. Canada and France both have life expectancies beyond the American life expectancy (According to the UN estimates, both Canada and France have an average life expectancy of 80.7 while the U.S. has one of 78.2). Likewise, countries that have a mixture of government and private health care (but a predominant emphasis on the government provided health care) like Norway and Japan also have longer life expectancies (Japan has an exceedingly impressive 82.6 years and Norway 80.2). While a few years seems quibbling, it is still a few years in the exact opposite direction implied by Mr. McConnell. I wish journalists would challenge politicians for sources a little more often.

Thursday, May 28, 2009

Quotations for the Ages

This is going to be my last Quotations post for a while. I am certainly not going to be dragging my Oxford Dictionary of Quotations with me to Germany, and tomorrow afternoon I am taking the train out to stay the weekend with my girlfriend's family before I fly out on Sunday for Goettingen. Thus, this is my last chance to make some headway through the 'B' section, so this is going to be a little longer than the usual list.

"It's not perfect, but to me on balance Right Now is a lot better than the Good Old Days." - Maeve Binchy, Irish novelist, 1940-

"We French, we English, never lost our civil war,
endure it still, a bloodless civil bore;
no wounded lying about, no Whitman wanted.
It's only by our lack of ghosts we're haunted."
- Earle Birney, Canadian poet, 1904-95

"The secret of politics? Make a good treaty with Russia."
"If there is ever another war in Europe, it will come out of some damned silly thing in the Balkans."
- Otto von Bismarck, German statesman, 1815-98

"If I'd known I was gonna live this long, I'd have taken better care of myself." - Eubie Blake, American ragtime pianist, 1883-1983

"Architecture should be at the head of the arts, not at the foot of the professions." - Reginald Blomfield, English architect, 1856-1942

Speaking of quantum mechanics:
"Anybody who is not shocked by this subject has failed to understand it." - Niels Bohr, Danish physicist, 1885-1962

"A fool can always find a greater fool to admire him." - Nicolas Boileau, French critic and poet, 1636-1711

Also, as a random aside, I thought it was neat to point out that Earle Birney, while born in Calgary, grew up in my hometown in BC. Oddly, I don't ever remember learning about him in elementary school. When you understand how small my hometown is, one would think it would at least be mentioned. We had a famous (for Canada) poet grow up in the area! Considering that really the only other noteworthy features of the area on a national scale are beer and close proximity to polygamists, I think a famous poet is worth a mention. Of course, there is a good chance that all my childhood friends who actually went to highschool in the area studied him in English class, and he was simply deemed too complicated to mention to grade 6 students.

Another Reason to Suggest Favourite Posts

Even if you don't think I am deserving of best science post of the year (a conjecture I would truthfully have to agree with... there are a lot of bloggers out there, many of whom write much better than I), there are two more reasons why I would appreciate some feedback on which posts you have enjoyed and which you have not. The first is that I am planning to add a sidebar element which will highlight a selection of five or so posts which might be worthwhile for new readers to have a look at. So far, I thought perhaps my series on top-down visual processing, my post on free will, and my post explaining the nature of brain waves might all be candidates. Of course, I am not always the best judge of my own work, which leads me to the second reason why feedback would be much appreciated. While a large part of my reason for maintaining this blog is the selfish desire to expound at length about whatever subjects strike my fancy, I also hope it will be an enjoyable reading endeavour. Therefore, I would like to get as broad a sense as possible from my current readership of which posts worked and which did not.

For those who have taken the time to send me your thoughts, thank you. For those who will do so in the future, thank you in advance.

Wednesday, May 27, 2009

Not My Puzzle

Thanks to Deus Ex Malcontent, I have been pointed in the direction of a fun puzzle put out by Empire Magazine. Called The Cryptic Canvas, you have a painting full of references to fifty films. Most of the films are relatively recent, but some of them do go back a ways. I haven't finished (my girlfriend and I made it to 29/50 before we decided to take a break), but there are some fun ones. You can save your progress and go back to it, so it is well worth having a look at.

Note: I am tagging this post with the puzzle label, but it is not part of the general run of puzzles I have been doing. So, as it should be obvious, I don't expect any emails with solutions. I will be quite confused if I do get them.


Through my internet wanderings, I have been made aware of a blog contest by a group called 3 Quarks Daily. They are currently looking for science submissions (with nominations ending June 1st). I am posting the link to the contest partly to help them promote it (they asked for bloggers to do so, and I think it sounds like a neat contest), but also partly for my own self-interest. After all, I write a blog (ostensibly) about science. So, in flagrant self-promotion, if any of my readers think I have done a wonderfully grand job of writing about a particular science topic within the last year, I would be very flattered to be nominated (they also allow self-nomination, which I am not above doing. So, even if you don't feel like nominating me but have some strong feelings about previous posts, feel free to send me an email letting me know what your favourite/least favourite posts are to give me an idea of what I might want to submit to the contest). After all, the prize is a thousand dollars, and the worst that could happen is I could be mocked across the amorphous lands of cyberspace as an amateur intellectual groupie. While that might hurt my feelings, I think it is a risk I am willing to take.

Saturday, May 23, 2009

Animal Intelligence Continued

I have been meaning to write an elaboration and comment response to my post on animal intelligence, but I kept putting it off for some reason. I think the main reason is because I find it to actually be a fairly daunting subject. There is a lot of nuance to it, as well as a lot of competing preconceptions and wildly differing interpretations by a lot of highly intelligent people. This makes it difficult to get a handle on the subject, but I think it is time I stop putting it off and give my attempt.

To start off with, I would like to briefly come to the defense of Noam Chomsky. Robert first brought him up saying that he "claims that humans are the only species that have the ability for language". Regan then adds his own comment in which he disparages Chomsky with a parting shot. While I think both Robert and Regan have the correct sentiment, I think there is a subtlety to Chomsky's claims that is being missed, thereby translating his claims into the territory in which they deserve the given disparagement. In the nature of full disclosure, I have not actually read a lot of Chomsky's work on linguistics, so much of my argument here will actually be based on Steven Pinker's book The Language Instinct. Throughout the book, Pinker draws heavily upon Chomsky's work and ideas, which is why I feel comfortable weighing in on Chomsky's defense. The thing is, as I understand it, Chomsky did not make the blanket claim that humans are the only species with the ability for language, but rather that we are the only species with a generative grammar based on an innate universal grammar. While I still think the statement that humans are the only species with this ability is still overly strong (there is evidence that some species of monkey are capable of a limited form of generative grammar, and our investigations into the cognitive abilities of other animals are far from complete), Chomsky's ideas are much more defensible than the patently false claim that humans are the only species with linguistic abilities (something which Regan rightly pointed out should immediately be rejected by anyone who has ever had a dog). Essentially, I think Chomsky is correct in pointing to our propensity for complex communication as one of the major cognitive advantages we have (though, like I said, I would modify his statements from we are the only species with these abilities to perhaps we are the most successful at utilizing them - much like one would correctly say a cheetah is the fastest land mammal instead of incorrectly saying the cheetah is the only land mammal to have mastered sprinting), but I do not necessarily agree with him on many of the subtler aspects of his analysis.

Speaking of unique cognitive abilities, this leads me to the apt question posed by jbrydle of whether or not our brains are fundamentally different from the brains of other creatures. The answer to this question is not straightforward, but my answer is that essentially we do not know for sure. I would now like to qualify that statement of ignorance with an extensive ramble of conjecture based on what we do know, and explain why that leads us to a state of ignorance. To start with, I would like to propose as an analogy the human hand. In plain appearance, we are capable of easily differentiating between a human hand and those of other species. However, in terms of function and arrangement, making the precise distinction becomes much harder. We are certainly not the only primate species with opposable thumbs, nor are primates the only mammalian species capable of gripping and manipulating objects with their hands (beavers, squirrels, and many other rodents have quite dextrous front paws). Likewise, elephants have adapted their noses rather than hands to the fine manipulation of objects, with the appendages on the end of their trunks capable of many of the same abilities as people. Outside of mammals, most birds have an opposable digit on their feet which allows them to manipulate and grip objects. Of course, this is quite a cursory and shallow view of the gross properties of the hand, but my point is that even something as basic and highly visible as the hand does not have a simple answer to what makes the hand of one species unique from others, especially when one is focusing on functional abilities rather than simple physical dimensions.

Moving from the hand to the immensely more complicated brain, therefore, one can see how the question is easily bogged down by nuance and qualifications. When one looks at the gross anatomy of the brain, the human brain does tend to have a more wrinkled outer exterior, known as the neocortex, than most other mammals (this increases the surface area of the cortex, since the functional setup of the cortex is a thin set of cellular layers. There are other anatomical differences as well, but I am going to try to avoid making this post into one long rendition of specific anatomical details). The neocortex is usually just referred to as the cortex, but there is more than one area of cortex in the brain as there is also a cerebellar cortex forming the outer layer of the cerebellum, which I have discussed in some detail before, so the neocortex is the term used to specifically speak about the more recently evolved cortical regions that comprise the outer shell of the cerebrum. It is also sometimes called the cerebral cortex, and it is only found in mammals. In non-mammals with advanced cognitive abilities (like many birds), quite different neural structures have evolved, often through the extension of primitive structures shared with our own brain. An example of this is in the different forms of visual perception between birds and mammals. In primates, most of our visual processing takes place in the visual cortex of the occipital lobe (the lobe at the back of one's head). There is also small midbrain structure called the superior colliculus (it is kind of like a little knob on the anterior dorsal surface of the midbrain), however, which plays an important role in visual perception. The superior colliculus provides a map of the visual field and is primarily used in spatial navigation. Its existence in the human brain allows for a condition known as type one blindsight, in which damage to a person's visual cortex has left them consciously blind. They are often, however, capable of fairly competent spatial navigation (such as walking through a room with scattered furniture without a large number of collisions) due to their superior colliculus. One interesting side-note to this condition is that because of the loss of cortical visual processing, a person suffering from blindsight is no longer consciously aware of the presence of light in their environment. Therefore, while they will be able to navigate an environment with the lights on, if you turn the lights off and ask them to walk back through the room, they will be unable to avoid collisions in the same manner (and will be rather confused about why they are suddenly having a much greater degree of difficulty).

Why am I focusing so much on the superior colliculus? Because in non-mammals it is called the optic tectum and it is particularly well developed in several predatory bird species such as owls, eagles, and hawks. Researchers have found, for example, that crows can visually differentiate between specific individuals among both crows and people. The ability to visually distinguish individuals is quite a complex task, and requires far more visual processing than that available in the standard mammalian superior colliculus. Thus, this rather long-winded example illustrates the first of many difficulties for anyone trying to definitively differentiate between the cognitive abilities of species. Because the brain is essentially a computational device providing behavioural control for an animal based on the interaction of its neurons, many different architectures can yield similar computational power. Thus, even if we have evolved novel cognitive abilities beyond those of our other ape relatives, it is extremely hard to definitively say whether or not those same abilities have independently evolved in other species.

This has grown quite long already, so I think I might stop it here. Hopefully this provides at least a little bit of explanation and feedback for the comments to my earlier post, as well as prompts some more thought and input on the subject.

Tuesday, May 19, 2009

An Interesting Link

I've spent the last day and a half working hard on a presentation I have to give tomorrow, so there hasn't been much time for blogging. However, this evening I read an article written by a guest writer at one of the weekly blogs which I regularly read, and it piqued my interest. I thought I would therefore share it with all of my readers. The article is by Steven Strogatz over at The Wild Side. As I have mentioned before, I have a growing fascination with the mathematics of dynamical systems, which is Strogatz's area of study. When I have a little more time I would like to delve into the references he used. In the meantime, I hope others find it as interesting as I did.

Monday, May 18, 2009

Monday Quotations

Taking advantage of the fact that I am back downtown today, here are some more quotations.

"It was deja vu all over again." - Yogi Berra, American baseball player, 1925-

"This island is made mainly of coal and surrounded by fish. Only an organizing genius could produce a shortage of coal and fish at the same time."
"We know what happens to people who stay in the middle of the road. They get run down."
"I read the newspapers avidly. It is my one form of continuous fiction."
- Aneurin Bevan, British Labour politician, 1897-1960

Speaking of NeuroLogica...

In my last post (linked for those who use an RSS service or the like) I recommended Dr. Steven Novella's NeuroLogica Blog for a more informed opinion on the medical issues I was discussing. While I primarily recommended him for his continued discussions of vaccination and alternative medicine, this morning he published a post about the Daniel Hauser story I brought up.

Sunday, May 17, 2009

Parents' Rights Revisited

Last August I wrote about one of the more contentious issues I have brought up on this blog, the right of parents to choose for their children. While I originally brought this up in the context of education and religion, the ongoing prevalence of vaccination 'controversy' necessitates another visit to the issue. Of course, vaccination is not the only aspect in which a parent's choices and beliefs directly affect the health of their child, as in the extreme case of Daniel Hauser. As with the a child's education, I don't know what the best policy would be. In contrast to some of my more libertarian inclined readers, I think I am more on the side of government advocation of treatment.

Essentially, I believe the issue flounders in a moral grey area for two main reasons. The first and most prevalent is the need to balance the rights and freedoms of an individual with the rights of those around him. While Daniel suffers from the non-communicable disease of cancer and his case is therefore not particularly related to this point, in the case of vaccination this is especially pertinent. Many vaccinations are only viable for administration after a certain age, thereby leaving infants and young children with a window of vulnerability. If there is a sizable population of non-vaccinated individuals of sufficient population density (for most communicable diseases, that density tends to be easily accomplished in even a small town of several thousand) they form a reservoir for the disease to persist. An example of this includes continued outbreaks of the measles in the United States through accidental importation of the disease from other countries finding a subsequent toehold in the growing population of non-vaccinated children, with the number of annual cases over doubling in 2008 (thanks Jenny McCarthy!). Therefore, there is the very real argument for a legal obligation to vaccinate one's children against communicable diseases to prevent the creation of a disease reservoir. I am curious what my more libertarian readers think of this balancing act (I'm looking at primarily at you, Mr. Brydle, but I know Cornucrapia leans on the more libertarian side of things than I do as well).

The other major component to the grey area is the right of the child to the best possible chances for a healthy life versus the right of the parents to act as surrogates for their child when making decisions before the child has development his cognitive abilities to a more adult level (this is the aspect that is much more pertinent to the case of Daniel mentioned above). When adults refuse medical treatment for themselves, the government in most cases accepts that. In the case of a parent refusing medical treatment for a child, however, I think the case becomes skewed. It is no longer the person making the decision who suffers the consequences (of course, I do not doubt that the vast majority of parents wish the best for their children, but it is still a slightly different situation).

There were more things I remember wanting to say on this subject, but I seem to be wandering in my attention. I am therefore going to post this as it is now, and hopefully others will volunteer their own thoughts on the matter. If you are interested in a more informed opinion than mine on the matter of public health and the fallacies of alternative medicine, I would recommend having a gander at Dr. Steven Novella's NeuroLogica Blog.

Saturday, May 16, 2009

Custom Search Added

I just thought I would point out that I have added a custom search to the sidebar just above Places of Interest. I thought it might be easier to use than the "What I've Written About" item when trying to find a specific post considering some of the topic labels have gone into the double digits with number of posts. I tried a couple sample searches myself to see how it works. While it doesn't seem to be that great, if there is an old post that you vaguely remember and for some reason want to reread but cannot seem to find, give it a go and it might help you track the post down (especially since my labelling practises have changed over the course of this blog's lifetime, so they are not always entirely consistent). As always, if there is something else in terms of functionality or subject matter you think should be around here, let me know and I will see if I can be accommodating.

Friday, May 15, 2009

Movie Review: Taken

I just watched the movie Taken. With an even more obscene ass-kicking to age ratio than Gran Torino, it was a little bit ludicrous. However, Liam Neeson is awesome as always and, while he may not have the physique that immediately makes one expect gratuitously well executed violence, his personal charisma makes it seem all right and plausible enough for a mind geared toward the suspension of disbelief (kind of like an older version of Matt Damon in the Bourne series). Anyway, I don't want to give anything away for those who have yet to see the film (and plan to), so I won't go on at length.

EDIT: I realise that the ratio ass-kicking:age should really be ass-kicking:(1/age), but saying "ass-kicking to the reciprocal of age" just didn't flow as well.

Ludwig Prandtl is Confused

Sorry for my continued failure to post things... I've just been dealing with this whole going to Germany thing (and my stitches came out on one side of my mouth tonight, so my damnable gums are killing me) in terms of booking flights and everything else. Part of the everything else is figuring out just what is going on over on the other side of the Atlantic, because it turns out my rejection letter for the Prandtl internship was possibly sent by mistake and I actually did get the official summer fellowship.

Of course, these failures of communication do happen even to the best of organizations. While talking to my girlfriend's dad about this kerfuffle, he told me a story about a friend of his from years ago (I have no idea what her name was, so I'll call her Sally) whose company decided she was worth grooming for upper management. Thus, Sally's company sent her off to Harvard or MIT to get an MBA (I actually forget which of the two schools they sent her to since both were mentioned in this conversation... anyway, both are impressive, prestigious, and damn expensive, so it really doesn't matter which it was). While she was at school, however, a bump in the market led to corporate cutbacks and Sally's whole department got laid off. Of course, the powers that be had no intention of laying Sally off, because she really wasn't part of the department anymore (she was, after all, coming back as a businesswoman rather than a lowly engineer). She was still listed as part of the department, though, while they waited for her successful completion of the MBA program, so whatever HR person got charged with executing the lay-offs went ahead and sent her the standard good-bye package. As ill luck would have it, Sally received her couriered and highly official looking dismissal package on the eve of the weekend, meaning an entire 72 hours went by before she was able to contact anyone to actually find out what the hell was going on. I imagine that must have been a pretty horrible weekend, because not only did it make her wonder if she had a job to go back to, it also called into question whether or not anyone was planning on continuing to foot the presumably hefty scholastic bill Sally was wracking up at her expensively impressive business school. Of course, things turned out fine in the end when Sally was finally able to contact her company's head office and find out she wasn't being laid off.

While I doubt the same set of corporate machinations played into my own situation of both acceptance and rejection, there certainly are a number of perfectly plausible possibilities more suited to an academic setting. Thus I am not lacking in resigned understanding, but I still would really like to know just what is going on. Anyway, I'm fairly confident things will turn out well in the end, but for now I am going to retire the topic until everything is actually sorted out. I will let everyone know what is happening once things are actually finalized.

Monday, May 11, 2009

Ludwig Prandtl Doesn't Want Me?

My recovery down time has not led to much blogging. I am still not entirely thinking clearly, as displayed by the last sentence of my most recent post: "Realizing our tendency to perform processing without consciously realising it..." Not only is it a poorly worded sentence, but I used two different spellings of the word 'realise' within a single sentence. That is quite embarrassing. I have made an effort to fix it, but I still might not be thinking properly. Therefore, I will continue taking a break from substantive posts for a while and instead comment on another development in my personal life.

As I mentioned before, I am going to be studying at the Max Planck Institute for Dynamics and Self-Organization in Goettingen, at least according to the series of emails from two of the professors there. However, I also just received an email today telling me that they are very sorry, but I failed to get one of the Prandtl internships. I am now rather confused. What I assume it all means is that during the course of reviewing the applications, the professors who emailed me last week decided he had some extra funding for his department, but Ludwig Prandtl doesn't actually want me. While I should still be going to do an amazing research internship in Germany, it does make me a little sad that it doesn't have Prandtl's name attached to it, especially after I excitedly made the announcement. Anyway, I will keep everyone apprised of the situation as things get more sorted out. Also, even if I'm not entirely up to making well-thought out and substantive posts, I still will try keeping things a little more lively around here in the next few days.

Saturday, May 9, 2009

Top-down Processing in Visual Perception Part IV: Ramifications

This is the final instalment of my series on top-down processing in the visual system (links to part I introducing the topic, part II discussing faces and anthropomorphizing, and part III discussing artificial edges). While I find the topics of vision and optical illusions to be fascinating in their own right, I think the analysis of perception and cognition is also vitally important. This is by no means an original outlook, as David Hume made the statement in the introduction to his A Treatise of Human Nature:
'Tis evident, that all the sciences have a relation, greater or less, to human nature; and that however wide any of them may seem to run from it, they still return back by one passage or another. Even Mathematics, Natural Philosophy, and Natural Religion, are in some measure dependent on the science of Man; since they lie under the cognizance of men, and are judged by their powers and faculties.
While couched in somewhat archaic English, Hume's statement strikes me as remarkably astute. In many ways, our brains function as vast pattern-matchers. Understanding the underlying cognitive tricks we use to analyse perception is an important endeavour for making sense of our own observations, and avoiding mistakes in our interpretation of experimental results. Of course, the most pertinent application of perceptual understanding is in automated sensory processing applications (like machine vision which I have discussed before), but as Hume pointed out, it also matters in the way our thought processes interact with every other endeavour. We must be wary of our tendency to anthropomorphize, or to view causal connections that are not actually there. Realising our tendency to perform processing without being consciously aware of it helps reinforce the necessity of mathematical, logical, and statistical tools on which to rest one's theories.

Friday, May 8, 2009

Alive and Recovering

Just a quick note saying I am currently in recovery mode. I am minus four to five teeth (one tooth was apparently a double) and in a fair bit of pain. Also, I'm a little loopy, being on a fair bit of Oxycodone and Acetominophen. Since I don't really have a lot to do other than lie around, watch television, read, and feel sorry for myself, I'll try to get some of the blogging that has been piling up around here done. However, I'm not sure I'm thinking all that well, so if the posts are a little rambling and sub-par, please let me know and I will try to rectify the situation. Anyway, it is time for me to try and get some sleep. Just as a passing comment, I have to say if some god designed us, he really wasn't thinking straight when he put wisdom teeth in our mouths.

Thursday, May 7, 2009


It has been a while since I put up a few quotations. Since I will be staying with my girlfriend's family for at least a few days while I recover from surgery (and won't be taking my book of quotations with me), this will be my last chance for a little while to put some up. So, here are a few things that have been said before.

"We started off trying to set up a small anarchist community, but people wouldn't obey the rules." - Alan Bennett, English actor and dramatist, 1934-

"Journalists say a thing they know isn't true, in the hope that if they keep on saying it long enough it will be true." - Arnold Bennett, English novelist, 1867-1931

"Men will not be content to manufacture life: they will want to improve on it." - J. D. Bernal, Irish-born physicist, 1901-71

"The future ain't what it used to be." - Yogi Berra, American baseball player, 1925-

Ludwig Prandtl Wants Me

This is just a quick note saying that it seems like I will be going to Germany for two months this summer to perform research at the Max Planck Institute for Dynamics and Self-Organization as part of the Ludwig Prandtl Summer Internship program. There are still some details to finalize (and plane tickets to buy), but it is all very exciting and daunting. I will be posting some more information as things progress later, as well as some information about where in Germany I am going to be and what I will be working on, but for now I have some other stuff that needs taking care of before I get my wisdom teeth taken out tomorrow morning and spend a few days hopped up on pain killers.

Note: For those who don't remember who Ludwig Prandtl is, as I have mentioned before, he is the man.

Tuesday, May 5, 2009


Yesterday was a great day which I forgot to announce. Why, might you ask? After all, I still have an exam coming up, so most of the day was spent studying. However, it was the fourth of May, and therefore it was Star Wars Day. Why is the fourth of May Star Wars Day, you might ask? Because on May the fourth you can say, "Happy Star Wars Day, May the fourth be with you!"

Happy belated Star Wars Day.

Sunday, May 3, 2009

Quick Shot of Physiology

One thing that I remember always puzzling me as a kid was why my voice sounded different to me when played back on a recording device than when I spoke, but everyone else's voices sounded pretty much the same. While I am sure there are likely other factors to this auditory dichotomy, while studying for my physiology exam I realised I had one of the reasons in front of me. I also decided it was interesting enough to share.

In order to transfer sound waves from the air to the liquid inside the cochlea (the inner ear structure which actually contains the nerve cells of the auditory system), there is a rather interesting structure called the middle ear. The primary components of the middle ear are the tympanic membrane (commonly called the ear drum), which vibrates in response to sound, and the three smallest bones in the human body. These bones are collectively called the ossicles, and individually are (in order from outside to inside) the malleus, incus, and stapes. The ossicles form a chain linking the tympanic membrane to the cochlea, thereby transferring vibrations from the air to the liquid inside. Due to the physical limitations of the middle ear, not all frequencies of sound are transferred equally. There is an upper frequency limit bounded by the mass of the ossicles (they can only vibrate so fast) and a lower frequency limit bounded by the stiffness of the system (as an interesting aside, one of the main reasons smaller creatures like cats and mice can hear higher frequencies than humans is because they have smaller and lighter ossicles than we do).

In addition to the membrane and the bones, there is also a pair of muscles: the tensor tympani which attaches to the malleus, and the stapedius which attaches to the stapes. These muscles can contract and increase the stiffness of the system, thereby reducing overall sound transmission and protecting the inner ear from possible damage due to loud noises (this only works effectively, however, on either loud noises which are expected or long-term noise due to the time latency of the muscle reflex). Increasing the stiffness of the system, however, does not reduce the level of sound transmission equally across all frequencies. Since this protective muscular reflex engages in an individual person when he talks, a person consistently has different frequency transmission properties when he speaks versus listening to an auditory playback of his own voice.

Now it is time to get back to studying.