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Educational Philosophy and PF Policy

  1. Jul 22, 2014 #1
    Note from mentor: This thread was split off from the one linked below. You may want to glance at it to see the context.



    This is also something I've wondered. Personally, I find the article a bit confusing and a bit thin on its exposition of "why" dispersion occurs. It says "dispersion is the phenomenon in which the phase velocity of a wave depends on its frequency, or equivalently when the group velocity depends on the frequency." I do not understand the way in which group velocity and phase velocity are equivalent to the phenomenon of dispersion. The article also seems to offer a second, different explanation of why dispersion occurs: because of wavelength dependence of refractive index.

    Why is group velocity mentioned? Does group velocity determine frequency of the light? How is the interaction with light of dispersive media different from the interaction with light of non-dispersive media? Is this a quantum mechanical phenomenon?

    It may also be productive to note that expressing a guess/partial understanding/reasons for an existing belief is the most efficient way to learn and seems like a good practice on forums, for the following reasons. Doing so allows the audience to understand the poster's level of background knowledge. It also helps to identify the specific point of confusion underlying the question. Moreover, a simple explanation is not always satisfactory because, in some cases, the question is driven by a desire to see the connection (or lack thereof) to previous, related knowledge. Finally, making a guess to an answer is perhaps most productive because it presents possible misconceptions, inviting readers to comment on and dispel those misconceptions directly.

    This type of back-and-forth dialogue (propelled forward by incorrect guesses and careful responses) makes a prominent appearance in some of University of Colorado's online physics resources. I believe much research has been done which demonstrates the superiority of (a) dialogue surrounding "wrong guesses" over (b) pure expository explanation in improving physics students' understanding of core physics concepts.

    On the other hand, it seems a bit counterproductive to focus on avoiding being wrong when asking a question.
    Last edited by a moderator: Jul 25, 2014
  2. jcsd
  3. Jul 22, 2014 #2
    I suppose, in the end of my previous post (#6), I have taken issue with this statement. Research in education demonstrates that teaching through incorrect guesses is highly productive and, in fact, yields better results than teaching through pure lecture/exposition. I won't continue on this topic given that it doesn't pertain to the original post, but perhaps it's worth finally mentioning that, due to its high level complexity, physics seems to be (in some ways) a favorite example for cognitive scientists and education researchers. The work I've read in those fields frequently invokes the teaching of physics as an illustrative example when approaching questions like, "how can we improve higher-order thinking among students?"
  4. Jul 22, 2014 #3


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    It's strange how such statements in non-Science seems to be accepted without the backing of references.* "Studies have been made" is another common statement. (I remember hearing a well known Education Minister saying, on the radio, "We are planning to do a study to show that . .blah blah blah . . . .")

    BTW, what sort of group was the subject of this study? They were, I imagine, already fairly high order thinkers and would have gone through the process of learning the disciplines involved.

    I agree that a there are many times when a motivated individual can make good progress by following their own line through a topic (tutorials are supposed to help with this). However, if they are to understand the actual content of the answers they get from their questions, they need to have some basic knowledge and be capable of assimilating facts and figures. Also, the Q&A system is highly inefficient - requiring very high teacher/Pupil ratios (see the numbers of PF members involved in some of the more fanciful Q&A threads on this forum, generated by just one individual). With lower ratios, it's just like herding cats. Didacticism still has its place. (Shoulders of Giants, is a phrase that comes to mind)

    *The studies of Piaget are accepted by many educationists but they don't seem to take into account the fact that the children in the study were largely the offspring of the great man's chums. (Bias or what??)
  5. Jul 22, 2014 #4

    Vanadium 50

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    The problem with guessing, as people who have been here for more than one day will tell you, is that it is very inefficient. It focuses the attention on things that are not the answer, and "no, that's not it" is not guaranteed or even likely that one will stumble on the correct answer. We have had threads go on and on explaining why the guess is wrong without ever explaining what is right. It's best not to guess.

    The guess in question suffers from several problems: it doesn't explain why there is a fixed energy loss, irrespective of frequency. It doesn't actually predict a bending. It predicts that you can't recombine the colors to make white light - it would get bluer and bluer. And, to get the degree of refraction needed to see a rainbow would imply we couldn't see the bottom of a swimming pool: water would be opaque. So this is wrong, and won't be helpful.

    Now that we are through this, I ask the OP again - now that you have read the article, is something still unclear?
  6. Jul 22, 2014 #5
    As I understand it, to the extent that someone is interested in knowing why a hypothesis or guess is wrong, this forum is an appropriate place to go. Maybe I've misunderstood or missed some of the rules. I don't see why it's unproductive to spend time addressing misconceptions or partial understandings on threads if this is something the original poster invites and wants. Perhaps these conversations are inefficient to the goal you mention of eliciting a correct, textbook-like, expository answer. But they are efficient to a different goal of understanding/pinpointing what's incorrect about one's current conception.

    It is true that I have limited experience posting. In my limited experience, threads are lengthened (and drawn off topic) by replies that critique the original poster's approach to posting/using the forum based on a personal opinion of how the forum should be used. Again, please correct me if this is more than a personal opinion and if it is the official forum policy? Do the forum rules say something along the lines of "no guessing and no discussion of alternative conceptions," or "no mixing of alternative conceptions with textbook-style exposition"? My understanding is that these conversations can be helpful to people when they are desired. Perhaps you meant "don't guess if you don't want to hear why your guess is incorrect," or perhaps I've misunderstood in some other way your posts.

    Regarding research, here's a short passage introducing the notion: "A refutational text introduces a common misconception, refutes it, and offers a new (alternative) theory that is shown to be more satisfactory. In this way, refutational texts are a means to create cognitive conflict."

    http://apa.org/education/k12/misconceptions.aspx?item=8 [Broken]

    Perhaps what you're more interested in: this website also cites the following further reading. Diakidoy, Kendeou, & Ioannides, 2003; Guzzetti, Snyder, Glass, & Gamas, 1993; Guzzetti, 2000; Hynd, 2001; Maria & MacGinitie, 1987.

    Here is a thesis investigating the role of refutational dialogue in physics videos. It also cites other texts on the subject (http://www.physics.usyd.edu.au/super/theses/PhD(Muller).pdf).

    Studies on the effectiveness of refutational texts have been done with subjects ranging from young children (around 6) to undergraduate students, as supported by the the above citations.
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  7. Jul 22, 2014 #6


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    You make some very good points about the value of interactive learning (interactive with people, that is) and it can be, unquestionably, be a good thing. Maybe you experience of dealing with such Q & A situations have been better than most. However, telling people a list of wrong answers, followed by the 'right' answer can often prove very misleading (they can forget which was the right answer, for a start). It can easily provoke the "Well, why was it wrong?" / Devil's Advocate response. This can lead to many blind alleys (and it has, in my experience), and running out of time to reinforce the right answers. I guess it depends up-on the emotional and technical calibre of the 'student. You are lucky if your experience has always been with suitable cases. On PF it is not uncommon to get some very petulant responses from dilettante contributors whose aim in life is mostly not to be shown to be wrong. I guess that there are good and bad ways of asking questions and or receiving answers in the spirit they are intended. We have all had to deal with some very awkward customers.

    By the bye, there is a statement in this post which puts the PF view concisely. There are many other 'Science' sites that do not have that view and they all tend to ramble around, getting nowhere useful. Have a look.
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  8. Jul 22, 2014 #7


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    Creativity and "educated guessing" are important in real research, but in order for them to be productive, they have to be accompanied by experimental testing and verification. In these cases, there's no one who knows the "real answer" yet!

    A good theorist not only says "Here's what I think might be happening...", but also "...and this is what I would do to test it experimentally."
  9. Jul 24, 2014 #8
    Thanks for the thoughtful response, sophiecentaur.

    The issue of timing certainly impacts what constructive approaches are available to a teacher in a classroom where the job is to teach many people rather than just one. Thoughtful devil's advocate can generate fruitful discussion by eliciting productive explanation of why a proposed idea is incorrect. In the learning process, understanding "why not X" is an important endeavor, as is understanding "why X." In a blog posting, it would seem that which deserves attention and reinforcement depends upon what the poster seeks.

    I do sincerely wonder, on these PF threads you mention with dilettante contributors, if the problem is in proposing a guess, or if the problem instead is in inflexibility/refusing to accepting being incorrect. Perhaps it would be highly constructive for established mentors and advisors like you, who make this site a valuable resource, to discourage inflexibility.
  10. Jul 25, 2014 #9


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    I think you will agree that we need to build on what is already known. We cannot disregard 'authority' in these matters. The only time it is likely that challenging the established view is when you actually understand it and what it is really saying. An individual will never be able to construct a personal Physics model from scratch. A large number of people seem to think otherwise and hang on to, quite frankly, loony models which have come from SciFi, Noddy TV and Hollywood. They are the ones responsible for my response to 'alternative thinking'.
    Rather than 'to discourage inflexibility', I would encourage informed flexibility. PF does this most of the time. If you have read a fraction of the number of PF threads that I have, you will have come across a number that are not well informed yet determinedly inflexible - in totally untenable directions.
    In the end, it's a matter of Horses for Courses and PF is a particular horse that works in the interest of mainstream Science and to help and encourage people who are working in that direction. Very few breakthroughs have been made by a different approach. Name one great Scientist who didn't do the official homework before that great discovery came along.
    So I don't think PF have got it too far wrong.
    Last edited: Jul 25, 2014
  11. Jul 25, 2014 #10
    I didn't slog through the whole original thread, so if this isn't relevant, please ignore.

    There are studies in "Student Centered Learning."


    I don't think guessing is the right word, but it is more of a philosophy of learning based on trying to answer questions before they've been formally "taught" the material. They learn by discovering through whatever activity they are working on. The success is largely dependent on how well designed the activity is.

    For example, you'd teach limits by showing how an approximation becomes better and better as the two points on a secant line become closer together. It's not taught outright, but through a series of questions. "Which do you think is the better approximation?" and so forth. The peer leader guides the students through the activity but is instructed not to teach too much. (They are peers, not teachers).

    So as peers, we were always taught that wrong answers were an important part of this process. That's how you find out what is correct reasoning and what is incorrect reasoning, or why certain topics are misunderstood. Yes, you will catch some people just guessing, but that usually means they don't know how to think about the problem yet, which is valuable information to have.

    The students sometimes hate it, of course, because they have to actually think and interact, rather than just sit and takes notes from a professor. But the effects on retention and grades and such have been non-negligible.

    -Dave K
  12. Jul 25, 2014 #11


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    Some of the views expressed on this thread may have been interpreted as being more harsh than intended.
    What you have written puts me in mind (as being totally the opposite) of some of the dire bits of video I have seen on YouTube with a mind numbing delivery of bookwork by a seemingly uninterested 'lecturer'. Thinking for themselves is essential for good learning and when it's directed usefully, it can be brilliant. But what PF (I think I can speak for many of us) doesn't approve of is random asking of questions, based on very dubious provenance. That is often not "student centred learning" but 'student, self-mis-directed rambling'. Worse still, it can end up in a spirited defence of of an unsubstantiated idea because the poster has taken offence at mistakes being pointed out.
    Brownian motion is not a good way of getting from A to B but, of course, being taken from A to B without having explored things on the way will leave one with no appreciation of where you've gone. Reason is called for in all things.
  13. Jul 25, 2014 #12
    I don't think there's an absence of learning here. But it is a somewhat more painful version of learning common on internet forums. The defensive reaction (by the asker) usually ends, followed by sulky silence and then later (maybe) acceptance. I've been through this a lot on both sides, as
    I've been doing the internet forum thing for a long time, probably 30 years if you count pre-internet (BBS) and proto-internet days. I've been both "uninformed asker" and "curtly responding know it all."

    When I got to the latter phase that usually meant it was time for me to leave the forum. But I learned quite a bit.

    -Dave K

    Of course the best way (I think) to learn anything is a combination of linear learning (taking a course) and more immersive type stuff. Sometimes that involves a little bit of getting in over one's head. A great way to learn.

    -Dave K
  14. Jul 25, 2014 #13


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    The shame of it is that so many people think they can go it alone, without the benefit of a guided syllabus. A good map of the subject gives you help about what questions to ask - plus the right vocabulary.
  15. Jul 25, 2014 #14
    Yes, so why do they think this?

    Possible reasons:

    Bad experiences with formal education
    time and money frustration
    perceptions of self, intelligence, age
    romantic notions of the solitary scientist...
  16. Jul 25, 2014 #15


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    I think highschoolphys may be under the mistaken impression that PF is some type of online school where our goal is to teach courses, it is not. We have discussions of well known, mainstream knowledge, and assist students with homework issues, we do not tutor and we do not give answers.
  17. Jul 25, 2014 #16


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    Those reasons and more.
    People think they can go it alone because Science is trivialised in the Media. A much more attractive 'Science' is portrayed in the media, which leads them to ignore the actual difficulty of doing proper Science.
    From what I have heard from teenagers, they really don't know what's real and what's made-up in films. Films are so well done that the simulation is reality in their minds. Even so-called Intellectual Broadcasters seem to think it's cool not to know much Science when they would all insist on knowing their Jane Austin from their Virginia Wolfe. Where are you now CP Snow? Were you right all along?
    Somewhere along the line, Science got it wrong where Sport got it right. Everyone knows there's no pain no gain in sport but, apparently, you can get through Science without any effort. It's the same with Modern Foreign Languages. They are now, more or less 'optional' because kids can't be arsed to learn them. In the UK, at least, the teachers are just not paid enough to encourage the right people to take up teaching. I know very few teachers of Physics who could sustain one of those 'ideal' interactive Physics lessons which have been mentioned in this thread. Give the kids a computer animation and that should do it.

    Having said that, I think there may be a chink of light at the end of the tunnel in the recent financial crisis. There may be a few more new teachers with calibre available at the moment.
  18. Jul 25, 2014 #17


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    I think the answer to that mistaken impression is:
  19. Jul 25, 2014 #18
    So its not just me that shouts at the radio when Jim Naughtie turns into a giggling idiot whenever the Today programme tries to cover a science topic?

    The great exception to this is Melvyn Bragg - the breadth of interest he displays in In Our Time is astonishing, he was wasted on the South Bank Show!
  20. Jul 25, 2014 #19


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    The blessed Lord Melvin can still be a bit of an ignoramus (relatively) with Science. He actually tends to be a bit less overbearing with Scientists because he's less confident. He can be sooooo bossy. Great prog though.
    That pratt Humphries still seems to think is 'good' not to know anything about computers. Baaaah!
  21. Jul 25, 2014 #20
    Yes Humphrys is even worse. Is this a good place to start a poll for most underrated BBC science presenter? My vote goes to Jim Al-Khalili.
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