Thursday, January 23, 2014

When Instructional Video Goes Bad

***Post updated with addendum at the end***

Let's say you're a high school biology teacher looking to do a segment on the nervous system for your class.  Maybe you run a flipped class, and so you head to youtube to find a good video to assign.  Or maybe you just want to brush up on the material so that you can teach it effectively.  Either way, you might find this video, entitled "The Nervous System" by Bozeman Science:

Presented by Paul Andersen, who was the 2011 Montana Teacher of the Year, the video has 150,000+ views and a 50:1 like/dislike ratio.  If you peruse the comments (looking past mine...) you'll see things like "You explained it better than my teacher", "This helped me so much", "way better than reading expensive textbook or any lecture in college", "You have such a knack for making a complex subject understandable", et cetera.

Seems like a great teaching tool, yes?

The problem is that the video gets many things wrong.  Here are five areas for improvement, detailing some of the errors along the way:

Getting the content right

Numerous factual errors are made, ranging from simple, easily-correctable mistakes:

Remember [the membrane potential] used to be -70 millivolts. And now it's going to be less that that. So maybe it's going to be -50 millivolts. [-50 > -70]
What happens is that you're going to get an influx of something called calcium. [The error here is that calcium is drawn as Ca+ instead of Ca2+]

to claiming things that are highly misleading, confusing, and often just untrue:

[discussing nodes of Ranvier] the message actually, it doesn't go all the way through the axon, it's able to jump from spot to spot. Because we put all the ion channels right here. [this is drawn with arrows suggesting that the "message" is literally leaping outside the axon and coming back in at the nodes. And the action potential does of course traverse the entirety of the axon, but is only regenerated at the nodes.]
Now what happens next, well we have to reestablish that gradient. And to do that we use something called the sodium-potassium pump. And so when you see light, you're sending literally thousands of action potentials down a neuron. Between each of those action potentials, the sodium-potassium pump is going to reestablish that gradient. [...] And then we have what's called the undershoot as it resets itself with the sodium-potassium pump. [This is profoundly wrong - the number of ions that flux during a single action potential is minuscule compared to the number of ions on either side of the membrane. Sodium/potassium pumps have nothing to do with the undershoot of the action potential].
All told, I went through the transcript of the video and found roughly 36 incorrect sentences, 25 misleading sentences, and 19 potentially confusing sentences.  (There were 94 correct sentences, and 138 filler sentences.  I probably missed a few too, so don't gotcha me if the numbers don't add up.)  You can view the whole transcript with my line-by-line annotations here:

Getting the level of detail right

The nature of the content that Mr. Andersen is trying to cover here makes the video trickier than it seems.  The meat of this video was on the neuron, the action potential, and the synapse.  The problem is that to fully understand, say, the action potential, the teacher must explain material from cell biology (neuronal membranes, protein channels), chemistry (ions, gradients, charge), and physics (voltage, current, etc).  It is, simply put, too much to explain the underlying concepts and link everything together in a single 17 minute video.

So what about a purely descriptive, superficial account?  After all, the learning doesn't begin and end with a single video.  Perhaps this can be used just to give people a "sense" for the material, an accurate portrayal of what happens without really delving into why and how.

I think such a video would be excellent.  Don't bother to explaining the detailed mechanisms of how things works.  A neuron, in such a video, is just a cell that receives little inputs in its dendrites that spread to the neuron's cell body and can trigger there the production of a big output we call a spike, which then travels down the axon and triggers neurotransmitter release at a synapse.  The neurotransmitters released by the presynaptic neuron causes the postsynaptic neuron to generate little inputs which spread to its cell body, etc.

But this particular video falls into a weird middle-ground.  It does the superficial, but then tries to go a little farther and explain some how and why questions.  But because there isn't time to fully build up everything from a firm understanding of the fundamentals, shortcuts are taken that inevitably lead to errors and likely generate misconceptions in the minds of the student viewer.  For example:

Now if you've ever heard me talk about neurons before you've heard this. I always like to say that nerves or neurons, a nerve is just a bunch of neurons together, that a neuron is simply a salty banana. And that allows you to remember where the ions are. And so what do you know about a salty banana? So this visual over here on the left side is super important to remember. We've got a salt grinder up here. It's going to put salt on the surface of the banana. Well what do you know about salt? Salt's going to be high in sodium. And what do you know about a banana? It's going to be high in potassium.

A clever mnemonic!  But wrong.  On a trivial level, potassium chloride is just as much a salt as sodium chloride.  But more importantly, this leaves the viewer with the impression that there's only salt outside a neuron and only potassium inside of one.  Wrong!!  It's a shortcut that bypasses a fuller discussion of concentration gradients.  There will be no deeper understanding imparted here in the minds of the student viewers, only a misconception.

Getting the organization right

One problem with this video in particular is its strange organization.  What purpose did the brief lesson on split-brain patients serve in relation to the rest of the material?  This quote particularly bothered me:

But I want to start with the big picture. And nothing gets more big picture in the nervous system than the brain.

Okay, so the brain is the largest portion of the nervous system, measured by number of cells it contains.  But that doesn't make it "big picture".  The big picture - which is never explicitly stated here - is usually expressed as something like, "The nervous system is like the command center for the body.  The nervous system is responsible for sensing the environment, both inside our bodies and outside of it, for integrating and processing that information, and for generating behaviors both mental and physical in response to it.  Everything you experience, think, or do is mediated by the nervous system."

Getting the script right

Many of the errors made in this video stem from simple language mistakes.  Stylistically Mr. Andersen speaks in a very easy-going and accessible manner.  However, he is often imprecise.  This avoidable imprecision leads to muddles like the following:

Action potentials work by polarizing a cell. In this case it's the neuron. They set up this polarization through sodium-potassium pump. If you remember that's a form of active transport. And then when they depolarize it by opening up these ion channels then we can send a message down the neuron.

Here he simply is unclear about what the antecedent for all the "they's" are, and it makes it seem like the action potentials are doing all of this stuff.  Content-wise, that makes all the statements in red incorrect (see my correction in the Google doc).

Getting the visuals right

Content errors in the visual cartoons and diagrams video producers make are common.  Here, for instance, Mr. Andersen compounds the content error he made earlier with Na+ and K+ ions by imprecisely animating what happens to them during an action potential:

This is a screengrab of when he gets to the end of the action potential.  My issue with it (and many animations like it) is that there's no mention that the actual number of ions that flux across a membrane in a single action potential is tiny compared to the total concentration.  But because he draws it this way, he feels compelled to explain how things get back to the starting state!  See this screengrab:

Now, he makes the content error that the sodium-potassium pump has to (via magic sparkles) reset all the ions.  If the animation were clearly drawn, if the concentrations were clearly explained, if the resting membrane potential had been taught first, if equilibrium potentials had been taught before that... none of this would have happened (this is also a prime example of how there's not a happy medium between complex and simple).

Takeaway Thoughts

  • Making a good quality instructional video requires careful consideration to the level of detail, the organization of the content, the accuracy of the content, the polish of the script, and the quality and accuracy of the visuals.
  • Students, teachers, and all viewers are not necessarily going to be able to tell accurate content from inaccurate.  People love this video, so feedback is not always going to be useful, especially since feedback will tend to only come from those who enjoyed the video enough to say so (those who didn't like it already clicked away to another page).



I emailed this blog to Mr. Andersen so that he would be aware of this feedback.  He has acknowledged in his reply to me that he has misconceptions about some of the concepts he presents in this video, and he is looking into re-doing the video when he has time.  (Understandably, he is doing a lot of videos and also teaching!)

I will publish his response here if he allows it, but for now I think you should all know that it was very heartening.  He clearly cares about his students and getting the material right and I have no doubt he can make a corrected video.

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