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[Phys-L] guided inquiry, unguided inquiry, and misguided inquiry



On 06/10/2013 12:51 PM, I wrote:

-- When checking things, check *all* of the plausible
hypotheses. The existence of a semi-OK model does not
preclude the existence of better models.
-- On the other side of the same coin, check each of the
hypotheses against *all* of the available data.
-- Furthermore, if a theory makes multiple predictions,
check each of the predictions. It is common to find a
theory that makes five predictions, four of which are
completely wrong. If there is no good reason for this,
i.e. if the logic behind all five predictions is the
same, it tells you that the one correct prediction was
fortuitous. Nothing about the theory can be trusted.

Pretty much everybody agrees with that.

The only problem is, it works better for experts than for students.
Students, pretty much by definition, don't have all the data, and
they don't have a full complement of theories to check against the
data. Therefore, if you leave students to figure stuff out on their
own, they will (in all likelihood) latch on to some oversimplified
theory that explains some undersized set of data. You can't fault
them for this. At this stage they have no way of knowing that their
simple theory will not survive when more data becomes available.

It helps if you, the teacher, point out other theories that also fit
the available data. Do this as early as possible in the process, so
that the students don't get overly invested in their oversimplified
theory. Alas, this technique has problems of its own. Students
will ask, reasonably enough, why they should prefer the fancy theory
to the simple theory. The answer is that /eventually/ the decision
will be based on additional data. In the meantime, the best decision
is no decision. That is, we ask students to recognize that both
theories fit the available subset of the data.
a) The simple theory has a /weak/ advantage, namely simplicity.
b) The fancy theory has a /weak/ advantage, based on trust, based
on the reputation of the teacher who says it will "eventually"
turn out to be superior.

Since both (a) and (b) are weak, unscientific reasons, both theories
must be considered viable at this stage of the game.

To summarize: The only way to keep the learning process from going
completely off the rails is to provide heavy, heavy guidance. Not
only is there guidance involved in telling students what experiments
to do, there must be guidance involved in feeding them additional
models to consider.

The only thing worse than unguided inquiry is misguided inquiry.

1) For example, consider the debate over the two-fluid model of
electricity versus the one-fluid model. As is so often the case,
Arons inadvertently provides an object lesson in how to do things
wrong. He marshals a great deal of evidence, and then comes to
a conclusion that is wrong twice over.
-- It is wrong to say that the one-fluid model is not viable.
It has been around for a long time (Franklin, 1747) and there
has never been a shred of evidence against it.
-- It is wrong to say that the two-fluid model is viable.
Before 1932 the evidence against it was slim, but now, since
the discovery of neutrons and especially positrons and other
subatomic particles, the two-fluid model is dead as a doornail.

Anybody who promotes (or even tolerates) the two-fluid model must
have a seriously deficient understanding of what /charge/ is. This
is not a trivial matter, because charge and conservation of charge
must be high on any list of the most fundamental notions in all of
physics ... maybe not as high as energy and conservation of energy,
but definitely on the same list.
http://www.av8n.com/physics/one-kind-of-charge.htm

2) As another example, consider the concept of thermal energy aka
heat aka caloric. Once again Arons leads us in misguided inquiry.
He shows how students can collect a great deal of evidence, leading
them step-by-step to a theory of caloric as a conserved quantity.
The evidence is entirely true ... just woefully incomplete. This
is exactly the sort of thing I was talking about above, namely
incomplete evidence that fits an oversimplified theory. Arons
seems to be unaware that for more than 200 years it has been known
that caloric (or heat or whatever you want to call it) is /not/ a
conserved quantity. Forsooth, it is not even a particularly well-
defined quantity; there are multiple inconsistent technical
definitions of "heat" in use today.
http://www.av8n.com/physics/thermo/heat.html

======================

IMHO this highlights a longstanding, serious problem in certain parts
of the educational system.

Often it seems the overarching principle is to teach the students
obedience and conformity. As a corollary, that means students must
be taught "the" right answer. The idea that there might be more than
one equally-good answer -- more than one equally-viable explanation
for the data -- is the sort of open-mindedness that must be crushed
at all costs.

We see this in the "sig figs" rules. The roundoff is so aggressive
that it guarantees that the answer is wrong, but TPTB don't seem to
care about that, because all students are getting the /same/ answer.
In contrast, if they didn't round off, there would be more than one
right answer, and that cannot be tolerated. Regimentation marches on!
Einstein had a word for this: Kadavergehorsamkeit.

Seriously, when was the last time you saw a textbook say "Here are
two equally good explanations for the data"? When was the last time
a teacher asked students to defer judgment as to which theory is
better?

I am quite sure such ideas /can/ be taught. They are taught routinely
in computer programming class, where there are maxims such as
-- "successive refinement", and
-- "premature optimization is the root of all evil".

With rare exceptions I don't like talking about misconceptions,
especially in front of naïve students, and there is no inconsistency
here. Asking them to consider a more-complete theory that they
might otherwise not have thought of is waaay different from asking
them to consider a wrong theory that they might otherwise not have
though of.