Debunking the assumption that "giving students the right answer shuts them down."

I am particularly interested in what happens when an instructor gives the participants "the right answer" and the participants recognize that this is happening.  I became interested (last summer) for two reasons:

1. I noticed that sometimes 'getting the right answer' promotes really productive conversations, whereas I think our community often assumes that 'getting the right answer' will shut students down.
2. I noticed that in cases in which 'getting the right answer' seems to shut participants down, I can look at the situation and see clues about why that might have happened.  (For example, participants communicate the expectation that the answer should be simple, whereas the answer is actually quite complex and/or takes a long time to communicate.)

Someone (Stamatis?) mentioned to me that Rachel had given a 'mini-lecture' in E2 and that they had caught an interesting conversation about Julie's experience of the lecture on tape.  So I clipped it!

Context: The first clip below shows the moment that the participants communicated to Rachel that they wanted an answer:

Teacher (in background): [Can you say if gravity is different than pressure?]
Rachel: Yes, gravity is different than pressure.
Teacher: Gravity is different from pressure, okay.
Rachel: Yes, Deb.
Debra: Would this be a time where you might just say, 'Okay, in the scientific community, this is what blah blah blah.'
Rachel (laughing): Debra is making a suggestion [...].
Debra: Can we just get the answer, yeah. (laughter)

I'm actually not sure which question they are asking Rachel to answer, but, for the next 10-15 minutes, Rachel shares her answer to this question and others that teachers ask intermittently throughout.

My best reconstruction is that the teachers have just done 'particle theater' (like energy theater, but tracking the matter through the system, rather than the energy) for the 'two-piston scenario.'  In this scenario, there are two equal-temperature (equal-N) pistons of gas side by side.  The gas in one of the pistons has been compressed more than the other.  In past iterations of this scenario, the participants have been asked which of the pistons will push a block further when released.  (Abby or E2 folks, am I getting this right?)

Rachel begins her lecture by discussing whether or not there is potential energy in the gas (that is inside the compressed pistons).  She says that if there were PE in the gas, it might be like particles 'squishing' when they bump into one another (in particle theater).  She says that she was raised to believe that the atoms of a (ideal) gas in fact are not squishy, although she acknowledges that if they were talking about a real gas, things would be different.

She goes on to say that another thing she was raised to believe is that gas particles are mostly in empty space, so that most of what happens is free travel between the walls of the container (as opposed to many collisions between gas particles).  In the smaller (more compressed) container, the number of collisions increases, and we (not sure if she means the teachers or the scientific community) conceptualized that as pressure.  She explains that each "bonk" exerts a push, and pressure is more like a push than an energy, even though pressure and energy are not unrelated.  She says that pressure hasn't been represented in either particle or energy theater.

Mary then interjects a question: If you were trying to show the difference between the more-compressed and less-compressed pistons in energy theater, would the difference be in the rate of transfer of energy?  Rachel responds that she thinks the difference would be in amount transferred, rather than how fast the transfer happened.  She says she'll have to think about the rate thing, but she's not ready to do that on her feet.  She draws the ETD below (including only air in chamber, piston, and block boxes), explaining her thinking as she goes:

She tells the teachers that there are the same number of Ts in the gas in the less- and more-compressed cases.  The Ts transform into Ks in the piston and are then transferred to the block.  In the more-compressed case, more Ts transform to Ks.  This accounts for it getting colder in the more-compressed case.  She states that this explanation does not account for the springiness in the two pistons, and it would need to.

Rachel also shares the reason that the instructors gave them this scenario: the two pistons are similar in many ways -- they have the same amount of energy to start -- but one transfers a lot of its energy.  In life, we want to move the block more, and the instructors would like the participants to be able to understand what it is about a scenario that gives us the opportunity to move the block more.  Rachel ends by saying that she feels "completely nude" because she gave them a ton of answers as well as the instructors' reason for asking them to think about this scenario.

Debra then requests that Rachel add the hand and the piston to her diagram for the more-compressed scenario.  (You can see that she does in the picture above.)  Rachel begins to talk through what this adds: There are Cs in the hand, Ks in the hand, Ks in the piston, etc.  Debra asks Rachel if the same number of Ks go into the piston for both the less- and more-compressed cases.  Rachel points out that she has to leave time for the system to come to equilibrium, since the hand that compresses the piston more is going to add more Ts, whereas Rachel has said that both pistons start with the same number of Ts.  (So she has to wait for the excess Ts to leave the system.)  Debra responds that this is confusing, and Rachel agrees.  They briefly discuss whether the Ts that are in the gas/air come from (did all of them come from the hand, or were some already in the gas?). 

Rachel instructs them to write in their notebooks silently for ten minutes.  The clip below starts just after this writing time.  Rachel approaches the table with (CCW from right) Julie, Don, Gail, and Jean.  Rachel sheepishly admits that she's not used to giving away answers, Julie responds by saying that she wasn't paying attention, Rachel leaves the table, and Julie and Don discuss the scenario in more depth.  Watch and enjoy!

Participants' response to 'getting the right answer':

Rachel: I never did that before [...].
(Julie laughs.)
Julie: What, just said straight out?
Rachel: Yeah.
Julie: You know what's funny is that I actually, my brain sort of turned off.  Which is probably why we say that's what we want but we don't actually want that.
Rachel: Mmhm.
Julie: Cause then I was like, 'Well, I don't agree with that cause we just did all this.'  And so what?  It doesn't have any meaning for me.
Rachel: Yeah.
Julie: And so I'm glad that...
Rachel: And [meanwhile] I just stand up there and you guys are like (stares off).
Julie: (Making noise and pretending to write something down.)  Yeah, writing it all down.  Totally.
Rachel laughs.
Rachel: Sorry [...] (walks away)
Don: For me, when she, see I needed to see those Ts go over, and once those Ts went over, and I saw that the energy was the same, then I started writing, cause that was the piece that I wasn't getting.
Julie: Wait, say, I'm...
Don: Well, do you see how there's 5 Ts in both.  See, the energy is the same in both of those...
Julie:...I agree...
Don:...The thermal energy is the same whether it's compressed or not, and that's what these guys were saying at the very beginning, and I wasn't agreein' with it.  And so as soon as we saw that transfer, and there was more energy was transferred...
Julie:...Oh I see, I see...
Don:...Then I was able to start to put this thing together.
Julie: And what was your, what's your thinking as to why more energy transferred?
Don: Why did more energy transfer? (Pause) Huh! (Laughs)
Julie: Right?
Don: Why did more energy transfer?
Julie: And then that's when we get confused with the force story because we say, "Pressure!"
Don: Yeah.
Julie: And pressure is a force and we can't say it.
Don: Right.  The reason why more energy transferred is more energy was put into it by the hand to begin with.
Julie: But we just said there's five Ts in both.
Don: Right.  You're right.  Never mind.
Julie laughs.
Julie: Do you see what I'm sayin'?  We still don't know.
Don: I know.  Then you get to that point when you can't. 
Julie: Yeah.
Don: It's like what do you do with it?
Julie: Right.
Don: Then you have to bring in particle theory.
Julie: Right, cause we both, we both got to a place where we can say, 'In the more compressed, more thermal is converted to movement, kinetic.'
Don: Mmhm.
Julie: And then we're good.  But then if we actually take that a step...
Don:...Yeah...
Julie:...Deeper.
Don: What causes the transfer?...
Julie:...Right...
Don: ...The number of hits per unit of time?
Julie: Right, which we don't even know what that really mean.  I mean, it doesn't mean a whole lot yet.
Don: Yeah, it's just like the drummer.  (Hits the table quickly, makes high-frequency noise:) Brrrrrr. Versus boink, boink, boink (hits table more slowly).
Julie: Except we said instead of it going boink, boink, boink, boink (hits table slowly, same-strength hits), it was actually like (hits table at different frequencies with different strengths).
Don: Yeah, all sorts of different random. 
Julie: Yeah, right.
Don: But if you look at it as a whole, it's more.
Julie: The take-away for me, it's mind-blowing to think that the speed didn't, that the change in speed wasn't necessarily directly related to the pressure component.  That it was more about collisions than it was, directly speaking.
Don: Mmhm.
Julie: There had to be like that half-step in between, you know?
Don: Yeah because we saw that the speed was the same in both of these, it wasn't about the speed, it was just the number of, more collisions more frequently.

What I see in this video: My interpretation of what is happening in this video is that:

1. Julie says she immediately tuned out when Rachel started giving her answer.  She attributes this to her disagreeing with Rachel's answer in light of her own thinking, so that Rachel's answer "didn't have any meaning for her."  I'm not sure whether she means that Rachel was answering a question that she did not have, whether she disagreed with Rachel's answer (and thus did not value it, although this doesn't seem right to me knowing Julie), or if she could not connect Rachel's answer to her own and so lost interest. 
2. Don, on the other hand, says that Rachel's answer responded to a 'need' that he had.  He says that (part of) Rachel's answer matched what another group said that he originally disagreed with.  It's not clear to me whether Rachel's authority convinced him, or whether she filled in a missing piece for him that made the other group's answer sensible.  (I'd guess the latter, because he points to a specific piece of Rachel's explanation that helped him to "put this thing together.")
3. Julie then asks Don a question about mechanism -- why does more energy transfer?  I LOVE Don's response.  His tone and facial expression when he says "Huh!" suggest to me that he is amused that he thought he got it but now recognizes that there is more for him to understand.  Julie and Don then engage in a beautiful discussion about why the more-compressed case transfers more energy.  Although they hedge a lot, their answer is mechanistic and thoughtfully negotiated: there are more collisions in the more-compressed case than in the less-compressed case.  I see so much physics in what they say: they negotiate that it can't be speed of the particles, since the two gases are the same temperature, so it must be the frequency; they use their fists to communicate how the strength and frequency of the collisions is different in the more- and less-compressed gases, and Julie (oh, Julie!) points to a distribution of strengths (speeds) and frequencies (Maxwell distribution, anyone?); and they reflect on the limits of their understanding as they go.

I can't decide whether this clip is an example of the answer 'shutting students down' or not.  On the one hand, Julie admits that she stopped listening when Rachel started 'lecturing,' and Don accepted the 'answer' without pushing for mechanism.  On the other hand, Don's noticing what he learned from Rachel's answer inspired Julie's question, which began this lovely exchange.  I think this would require more careful study -- including understanding what happened around this conversation -- so I'm flagging it for future reference.