Methods of Encoding - Movement

In a college biology class, I was learning about the difference between mitosis and meiosis. If you have learned this concept yourself, you know it can be very confusing to keep the movement of the chromatids straight at each phase of the process.  As I wrote last year, images are helpful, but because it is dynamic process, they were not helping me see how things moved from on phase to another. The professor knew this, so he had us all stand up. We began in a clump at the center of the room (cell). As we moved into prophase, metaphase, anaphase, and telophase, he had us move toward partners and away from other groups until we finally had split into two classes (daughter cells). He was taking advantage of movement for encoding.

Was it because we were a room full of kinesthetic learners?  Nope.  At the time, because I didn't know learning styles were a myth, I would have called myself an auditory learner, but experiencing the motion of each phase did help me encode each one better than words alone (or even words with images) would have. I would like to point out, though, that the movement alone wouldn't have been helpful without explicit explanation coming first.  The movement helped cement the learning, but it did not teach mitosis to me.

Gesture has become all the rage, but there is still much research to be done on its effectiveness.  As with a lot of things in science, the results of experiment are very specific to content and context.  So, the conclusion seems to be that some types of gesture help some kids learn some content. Given that there is zero cost to implementing it and it will help a bit with engagement, I say it is worth trying.  It can be as complex as the "dance steps" we did for mitosis.  It can also be as simple as having students hold up a circle with their hands to indicate a zero.

Content which involves relationships in three dimensional space benefit from use of moving the body to represent those relationships.  Mitosis is one example, but as a physics student, I was taught the "right hand rules" to help with analyzing the relationship between electrical current, magnetic fields, and force.  Each pair of those has a perpendicular effect on the third one.  Unless you are already quite familiar with this topic, that explanation was probably confusing.  It will help if you see this picture, but nothing helps as much as students twisting their hands to the orientation of the set up described in the problem.  One only needs to walk into the test on this chapter and see students silently doing that exact thing to know how much it helps.

Since the research is fairly new, there are a wide variety of hypotheses about why it works and no solid conclusions.  Some have posed that it provides an offload to working memory.  If I can hold the number 3 that I'm going to need in a second in my hand, I don't have to hold it in my brain.  I've done this without meaning to while teaching cycle classes.  If I know we are going to increase tension 6 times, I'll have four fingers resting on the handlebar, so I can tell my class, "This one is number 5 of 6."  If an anatomy student is pointing at her own femur while rehearsing proximal and distal attachments, she won't have to look back at a diagram to remember which part she is dealing with.  The gesture might serve as a physical mnemonic device, reminding you of the thing it symbolizes. Like I said, the research is too new to have drawn any meaningful conclusion about the mechanisms just yet.

We all know the power of muscle memory for physical activities, like dance and sports.  Muscles are meat, so they don't actually remember, but a well myelinated pathway from repeated practice is how we make learning permanent. 

If you want to implement this is your classrooms, start slowly.  There is no need to insist that every piece of content have a motion or gesture, and the research doesn't support that anyway.  I would suggest the use of movements and gestures will only be really helpful if they are natural.  If you have to think hard to come up with a gesture and force it to fit, it will likely not be beneficial.  

Methods of Encoding - Pairing Visuals

A popular applause line at education conferences is "Nothing has changed in education for 200 years!"  It gets everybody fired up for the "new" thing that the speaker wants to promote, but it simply is not true.  I taught for 25 years and was, of course, a student for 17 years before that.  And just in that relatively short time, education has changed dramatically.  The fact that we sit in rows at desks notwithstanding, my grandparents wouldn't recognize most of what happens in classrooms today.  Have you ever picked up a textbook from a hundred years ago?  It is only a few millimeters thick, has tiny font, no pictures, and little spacing - printing was way too expensive to waste precious space.

Tech has brought about a million flashy changes.  Kids can make videos of their own, but the most profoundly effective change was probably the simplest - pairing visual images with explanations.

I know you were expecting something more fun, and I'm certainly not going to be able to sell this to people at conferences.

But it really is this simple.  

Is the impact because we are addressing the learning styles of visual learners?  

No.  That isn't a thing.  You aren't a visual learner.  Stop saying it.  Your child is not a visual learner.  Just stop.  Stop it now.

The reason pairing visuals with explanations is so powerful for encoding information is because we ALL essentially have two pathways in the brain for processing information. Verbal and images.  

Verbal information can be spoken or written - it doesn't matter because they are both words, and words are processed by the verbal pathway.  Images are, of course, pictures. Or animated video. Or even pictures we imagine in our minds.  When these two processing centers are used in conjunction, they compliment each other, and encoding is more powerful.  It's called Dual Coding, and it helps EVERY student (and is, I believe, one of the reasons the learning styles myth just won't die - people don't understand the difference).

But just as I said last week that not all explanations are created equal, the same is true of how we pair our images and explanations.  I'm not talking about clip art, here. I fell for this for a while, so I want to be clear that some images serve as nothing more than a distraction.  If I am teaching physics students to solve kinematics problems (the relationship between acceleration, distance, and time) and include a picture of a race car just for the sake of having a picture, that is NOT dual coding.  If I put in a gif of a race car going past over and over again because I think kids like gifs, that is NOT dual coding.  Those images are impeding learning, not enhancing it.

An image that helps your explanation is one in which the image provides detail, context, or anchors that words alone cannot.  A photograph of a flower in a science book is unlikely to help (unless it is just to show types of a certain varietal), but a labeled diagram of a flower with lines pointing to the structures being named can enhance a paragraph in which those structures are explained.  

The less eye movement required to take in the information, the better.  An image with direct labels is better than one with letters corresponding to words elsewhere on the page.  In very detailed pictures (like anatomical drawings), this may not be possible, but put it as close to the image as possible.  Ideally, the words and image can be processed simultaneously without splitting your attention.

What's nice about understanding the difference between the truth of dual coding and the myth of learning styles is that you don't have to pressure yourself into making three different lesson plans for the same subject.  You can design one high quality lesson with modalities that fit the content, and ALL students will benefit.

Methods of Encoding - Explanations

Despite all of the fads encouraging "guide on the side rather than sage on the stage," the most common form of instruction remains good, old fashioned explanations.  

Why?  

Because the most effective, efficient, and straightforward way of getting information from the head of someone knowledge to the head of someone without it is to tell them.  We know it works from research, but even if we didn't, we would know it works from the thousands of years of history in which oral tradition was the only option available (perhaps paired with a drawing on a cave wall, but we'll talk about that next week).

So, most of the encoding that happens in schools is done through explanation.  That means, we should invest a lot of our professional development time on getting explanations right.  Anyone who has ever helped their dad with a home repair, only to misunderstand and mess up the project, knows that explanations aren't all created equal. 

Good explanations engage listeners through hooks, brisk pacing, frequent checks for understanding, analogies, and clear sequencing.  

Hooks:

Think of the best sermon, stand up comedy routine, or TED talk you have ever heard.  Chances are, you remember how it started more than any other part of it.  And that's likely because excellent speakers start with something to get your attention.  Sometimes, it's a quote or especially interesting fact, but more often than not, it's a story.  Better yet, it is the first half of a story that they will finish later in the speech.  People who want you to keep listening are wise to pique your curiosity and make you want to know more.  Teachers, pay attention to the world around you, and you will see myriads of opportunities to connect something you have seen to your content.  "Last week, I saw a bird fly into a window, and it made me wonder, 'What makes glass transparent?'" will draw students in far more than, "Today, we will talk about what make glass transparent."  An English teacher can tell a story about an argument they overheard as the lead in to a discussion on literary conflict.  Even in math, there is a way to turn a variable into a character.  Check out this TED talk from Tyler DeWitt on using story telling in his science classes to help his kids care about what they are learning.  The point, if you don't grab their attention early, you don't stand a chance of keeping them engaged when the lesson gets harder.

Brisk Pacing:

I confess that I had not thought much about pacing (other than my own need to fit the whole lesson into a class period) before reading Zach Groshell's book Just Tell Them.  In his role as instructional coach and consultant, Zach has observed hundreds of lessons and says that one of the things he has noticed most is pacing that is too slow.  He's not advising that teachers speak at lightning speed and blow past checks for understanding (far from it if you have ever seen him present).  He is simply advising that we not dwell forever on one point if it isn't needed and eliminate things that aren't necessary for learning.  I'll add that a lot of classroom management issues could be pre-empted with faster pacing as well and free up time for retrieval practice at the end of the period.

Checks for Understanding:

No matter how good an explainer you are, there will be misconceptions in the minds of your students.  They miss an important word that changes the meaning of a sentence.  They activate some partially relevant piece of prior knowledge and make an inappropriate connection to it.  Their lack of background knowledge or vocabulary makes them have only a partial understanding.  There are lots of ways misconceptions can sneak in to your excellent lesson.  And misconceptions are like weeds; they grow out of control alongside the good information.  And, they are easier to uproot if you catch them early.  For that reason, your explanations should include frequent checks for understanding from as many of your students as possible.  Don't just call on the kid with his hand up.  He only raised his hand because he was confident, so he's almost always going to be right; and that is almost always going to mislead you into believing that everyone understands.  You can whiteboards, paper, choral response, cold calling, or digital tools, but you must ask them to answer questions that show their thinking.

Analogies, Metaphors, and Similes:

The best way to understand something is to connect it something else that you already understand.  Using analogies in your explanations help content to stick.  Chemistry teachers, make the reactants and products of a chemical reaction people at homecoming trying to find the right dance partners.  

Algebra teachers - "Think of the variable like a loner.  He just wants to be by himself.  He's trying to get everyone to go away by doing the opposite of what they want to do."  Kids understand that a lot more than "To isolate a variable, employ the opposite operation of those terms already connected to the variable."

You do have to be careful with analogies.  Because they are so powerful, they are sometimes the part of your explanation that sticks the best.  I used to describe dissociation (the process of ionic compounds dissolving in water) with the analogy, "It's like a married couple going to a party.  They wife goes one direction and the husband goes another to mingle during the party.  But, they aren't divorced (to make the point that chemical decomposition has not happened) because they come back together at the end of the party.  One the next test they had, several students gave me a detailed answer to the question, "Describe the process of dissociation" without ever mentioning ions or polar molecules.  They told me a lot about mingling at parties.  That was a good reminder for me to constantly circle back to the content to prevent only encoding the analogy.  

Sequencing:

Perhaps the most under-appreciated part of explanations is the sequencing of information.  I think that is because most of us plan it rather unconsciously.  But it is worth taking a few minutes to think about as you plan your lessons.  Will "A" make sense if I teach it before I teach "B"?  If not, re-sequence.  

There are time when this is difficult, especially as students get older and the content becomes more complex and self referencing.  I often found myself saying, "But we'll talk more about that next semester."  The key then is to explain what they NEEED to know in order to understand what you are teaching them today.  It's okay to say, "There will be more on this later" without trying to teach all of the coming concept.  In fact, I found that my especially curious students were excited to know that things would connect up later.  I also really liked making that explicit when we got there.  "Hey, remember that thing from two weeks ago?  See how it all comes together now?  Isn't it cool how everything depends on everything else?"  Once a student made the connection for me.  I was teaching Net Ionic Equations, and a student said,"Man, this one thing has stuff from like four different chapters."  I had not recognized that yet, but he was right.  If I had tried to teach those too early in the year, it would have been an absolute mess. 

Explanations may be the most straightforward way to teach, but it takes time to plan effectively.  I recommend two books to help with this process.  The first one is one I already mentioned - Zach Groshell's Just Tell Them.  Zach practices what he preaches, so it is a short book that is practical, to the point, and leaves out the fluff.  

If you have a little more time and you want to deep dive into the science behind explanations, I recommend How to Explain Absolutely Anything to Absolutely Anyone by Andy Tharby.  It is a little more dense than Zach's, but it is chock full of great connections to cognitives science research.  Together, these two books will up your explanation game in a huge ways.

Practicing What You Have Not Learned?

I discovered a delightful show on YouTube during lockdown.  I say "discovered;" it had already been on for fourteen years before I found it.  It's called Would I Lie to You?, and I'm honestly not sure I would have gotten through the hybrid year without it. I'd come home at the end of the day a puddle of exhaustion and eat dinner watching Colbert, after which I would watch a couple of episodes of WILTY and laugh until I cried.

Last week, a more recent episode featured a story in which one of the participants claimed to have made a sculpture of a girl he liked (like the girl in the Lionel Richie "Hello" video).  Spoiler alert in case you plan to watch the show:  This story turned out not to be true.  But, as he was selling his tale, one of the questions that was asked was, "Do you have experience with sculpting."  His answer was, "No, but I figured you learn by practice."

This could just be the education nerd in me or a reflection of the age of the young man telling the story, but all I could think was, "Well, there's someone who has been exposed to too much "discovery learning."  Here he was thinking that the highly specialized skill of representative sculpture (not an abstract, but the face of a girl he was trying to impress) was something he could figure out on his own by trial and error.  It's a good thing this story wasn't true because I don't think he would have won the affections of this girl with a "learn by practice" sculpture.

I think the reason this stuck with me was the word "practice."  There are two parts to learning.  Encoding and practice.  

Whether knowledge or skill, encoding must come first.  I'm not saying it has to be learned from a professional teacher, but no one is truly self-taught.  They get their initial knowledge or skill from somewhere.  Whether it is from reading, direct instruction, modeling, or TikTok video - something must first be input and encoded.  Practice, by definition, is the repetition of something already learned.  Practice is important as it myelinates the nerve cells and solidifies the skill or knowledge, but it cannot come first.

As the great Tom Sherrington put it in one of his recent blog posts, "You need to make some initial pathways in your brain (some actual physical connections) before we can worry about strengthening them through application and practice."

We have underemphasized this in recent years with the talk of retrieval practice at every conference.  I'm downplaying retrieval.  We must have both to make learning stay in long term memory.  But let's talk more about good methods of encoding.

I'm going to attempt to do my part by making the next few posts about methods of encoding.  So stay tuned this summer.

The Dignity of All Work

I once had a principal who liked to tell what he believed to be an inspiring story.  His junior high school was right across from a textile mill.  Once, when he was not performing up to expectations, his teacher made him look out the window at the mill and said, "If you don't get good grades, you'll have to spend your life working at the mill." He then, apparently, put his all into his studies so he wouldn't have to livet hat life.  Every time he told this story, I cringed (and not just because my grandmother and brother both worked in textiles) because he was taking dignity from one kind of work in order to inspire another kind.  I didn't have the kind of relationship with him where I could go to him and say, "You should be glad there are people who don't think their above working in textile mills or you would be naked right now," but I always wanted to.

Across the country, the school year is winding down.  Students are graduating from high school, and they are taking a wide variety of paths.  Some students are excitedly celebrating their acceptances to four year universities and already have plans for post-graduate degrees.  Others are nervously waitlisted or accepted on a deferred basis.  Some are going to community college while they take general ed classes and figure out what they want to major in.  Some will get vocational training in a technical school.  Some will begin entry level jobs and work their way up.  Some will wait tables. Some will design the next big video game. 

And some will work in textile mills.

Every kid's path is different.

Let me put it another way for those who need to hear it differently.

Every path is valid; yours is not superior.

The society in which we live is inanely interdependent, and we need people to do all of the jobs.  If your garbage isn't picked up one week, that's inconvenient, but if it isn't picked up for two month, that's horrifying.  Be grateful for your trash collector.  You have a coffee addiction?  It's a good thing there are people who don't see service jobs in coffee shops as something to be sneered at, or you would have to figure out how to do it for yourself.  When you need your air conditioning repaired on a 95 degree day, your son't degree in accounting or contract law won't do you much good, so you are going to shell out good money to someone with skills you don't have.

Let's not forget that college for most is a relatively new thing.  Just one hundred years ago, going to college after high school was the exception, not the rule.  Neither of the Wright brothers graduated high school.  Frederick Douglas wasn't allowed an education.  Yet, those people managed to have great influence through their work. Some of our founding fathers attended college, but not all of them did. Going back farther, Jesus was a carpenter, and Adam and Eve were farmers.  

Let me be clear.  I am not against against people pursuing degrees.  I did.  If what you want to do requires a degree or two or five, I'm all for it. I hope your school prepared you well for that choice.  After all, I don't want a doctor or lawyer or engineer who is "self taught."  I'm saying that it is not the right choice for everyone.

We need all jobs. Not everyone needs to go into debt to get one.

It's an unappreciated truth that some paths are not linear.  You may do one thing for a few years and then make a different choice.  It's always been the case that few people do the thing they majored in for their entire career, and that is becoming increasingly rare in recent years.  Sometimes, interests change.  Other times, market forces and government whims force change.  Injuries, the birth of kids, divorce, aging parents who need care, and a million other things can spark big change.  The idea that a high school senior has their whole life planned out when they graduate is fiction.  When I was in college, I worked as a janitor in an arena and in child care. I was a teacher for 25 years, but between two schools, I worked at a mortgage company.  Now, I work at the YMCA.  All of these jobs helped shape who I am, and the lessons I learned in each of those jobs were carried with me into the next one, making me a better employee and more interesting person.

In 2018, pictures of Geoffrey Owens, who had played Eldin on the Cosby Show, went viral.  Why?  He was bagging groceries at Trader Joe's.  Acting isn't always consistent income, sometimes including long time periods between gigs; so he was making ends meet by working at the grocery chain.  The same people who criticize so called "Hollywood elites" for being out of touch went online and mocked him for doing work they considered beneath themselves.  He praised Trader Joe's as a great place to work and said, "I'm not ashamed of working at the grocery store. No job is better than any other.  Every job is worthwhile and valuable."

What is important is that you do something that is honest, fulfilling for you, and contributes to society in some way. You are meant to honor God with whatever He has put in front of you to do each day, whether that is brain surgery or car repair. Whatever God has given you to do, use it to glorify him and serve others.  The reformer Martin Luther is credited as saying, "A dairy maid can milk cows to the glory of God."  He said that she is "glorifying God just as much as a preacher in a pulpit preaching a sermon."  Civil rights activist Martin Luther King, Jr. described all work as significant, saying, "All labor that uplifts humanity has dignity and importance and should be undertaken with painstaking excellence."

After communion each week, my congregation prays the same prayer.  It says, in part, "And now, send us out to do the work you have given us to do."  If we do that, our work has value, dignity, and importance, no matter what it is.

Congratulations to the class of 2025.  Whatever you have chosen to do next, and wherever your path may lead you, do it well.  Use it to glorify God, and serve others.

Tribute to MY class of 2025

"In life, you don't have to have all the right answers if you are asking the right questions." 
- Salutatorian Katherine McKinley May 23, 2025

The class of 2025 is here, in their regalia, ready to head out into the world.  I know some schools still have a few weeks left, but Memorial Day weekend marks the beginning of graduation season.  While they look forward, I can't help but look back.  As an 8th grade science teacher, I taught 54 of this year's graduating seniors during the hybrid year.  There is a bond that can only be created by that kind of stress.  Some were at home while others were in the room with me, although we were standing as far apart as a classroom space would allow, we were in it together. Masked and separated by plexiglass, but with a common goal and a common spirit. They had been home since March, so they were excited to see each other again and a little more nervous about what the year might look like than normal.  But my biggest memory of them was how game they were.  Because we were doing EVERYTHING in new ways, the most common words I said in the first month of the 2020-2021 school year were, "We're going to try it this way.  If it works, we'll keep doing it. If not, we'll try something else."  And they rolled with it, adapting like champs.  At the end of the year, just before they walked out the door, I said, "This year has been hard, but I want to thank you for not using the power you have to make it harder.  You guys made it fun."

While all 54 of the ones I taught are special, there are a few that stand out in my memory for different reasons that year, and I want to mention a few.

Collin - Collin is a hard worker, but he is also a goofball - a teacher's favorite combination.  Because his elderly grandmother was living with them, he spent the first six weeks of the school year joining my class from his bedroom.  At that time, he was the only one virtual in that particular period, so I could see him full screen.  Every time I looked at the screen, he was wearing a different hat.  He switched from sombrero to cowboy hat to propeller beanie as though it were totally normal.  At one point, I looked up to see that he had a yellow duck perched on top of his head.  Since I was the only one who could see him, this wasn't a show he was putting on for friends or an attempt to be disruptive.  It was purely for my entertainment and his.  He says he doesn't remember this, but I do. In a very stressful time, it was a lovely moment of joy.

Marley -  I heard so much during the pandemic about how masks prevented people from telling if you were smiling.  Marley proved this not to be true.  I'll set aside the fact that anyone who smiles only with their mouths is a psychopath (Try it; it's pretty much impossible). Being back in person outweighed any effect not seeing the lower part of the face had.  Kids communicate a lot of information in a number of subtle ways, and that had been lost during the virtual spring.  Online, I wasn't getting much nonverbal communication at all; in person, I was seeing body language and hearing sounds of confusion or affirmation.  Marley, in particular, smiled with every part of her being.  Her eyes sparkle; her voice is bright and genuine; her body language is open.  She gave this joy to everyone during the pandemic, and she has continued to do so in the four years since.  

Emily - Emily is an artist, and that's how she processes the world around her.  She draws pictures -  pictures of her pets, pictures of her thoughts, pictures of whatever she's looking at - she fills her sketchbook with lots and lots of pictures.  During the stress of the pandemic, she became a giver of  pictures.  I had a stuffed toy lemur named Gus in my classroom, and she drew a picture of him during class one day to gave to me after class.  One morning, as she was coming into the building, she asked me what my favorite animal was.  When she came to class that afternoon, she gave me a drawing of a panda sleeping on a tree branch.  It was stress relief for us both, and I still have those drawings at home.

Haolin - If you are a person who nods along during a presentation, class, or sermon, God bless you.  When presenting, it can be hard to know whether what I am saying is landing with listeners, and getting that bit of attentive feedback is useful.  Haolin is the world champion of nodding along.  He sat in the back of my classroom, in my right peripheral vision, nodding and saying, "Yeah, yeah.  Mmm hmm."  That little bit of affirmation was so encouraging, and while I have thanked him for it, I don't think he'll ever understand its true value for me.

Kate - The quote at the top of this post from Kate's salutatory address stood out because of what Kate's questions meant to me during the hybrid year.  She was in my 6th period class.  By that point in each day, teachers were exhausted - not just tired, but depleted of energy.  Yet, Kate continued to be curious.  She asked interesting questions.  She truly wanted to learn more about whatever topic we were covering and had questions about how it applied to things she saw in life. Each day, she reminded me that I was still teaching - not just surviving the year (or the day) but actually teaching students who wanted to learn.  I could never thank her enough for that, and I hope she continues to view learning that way throughout her life.

Class of 2025, I can only imagine what it would have been like if I had been teaching a different set of 8th graders during the most difficult year of all of our lives.  As hard as it was, your spirit made it worth every exhausting minute.  

Thank you.

Wait Time - The Secret Sauce of Thinking

My first observation as a teacher was done by my university advisor.  She had a lot of good thoughts and constructive criticism, but the best was about wait time.  Professor Klehm said, "You are not waiting long enough after you ask a question.  Count to three before you start looking for hands." 

Observers and feedback givers, take note.  This is the kind of effective, practical, simple, and usable advice every first year teacher needs.  And the longer I taught, the more I recognized how right she was.  In fact, she probably should have told me to count to a higher number.  

Increasing wait time would improve all of our classrooms because wait time is think time.  

Imagine. You are sitting in a class or a meeting.  The leader asks a question.  Your ears hear it, but it takes a moment for it to be really heard by your brain.  Then, unless it is a question you get asked frequently and have a memorized response for, it takes a little time to consider what the answer might be.  How long do you think that process might take?  What if the meeting leader expected an answer from you in less than a second?  Or less than half of a second?  Stressful, right!?!

Well, here's the bad news.  

In data compiled from thousands of teacher observations, the average wait time between a K-12 teacher asking a question and then expecting students to answer, has been calculated to be 0.7s.  If that's the average, that means some teachers are waiting for less than half a second before expecting kids to have an answer.  Some were as low as 0.2 seconds!  Just for context, it took 0.155s for Usain Bolt to get out of the blocks after the starting gun was fired at the Rio Olympics.  So, some teachers are expecting Olympic sprinter thinking from middle schoolers.  

Then, they call on the first student to raise their hand, and thinking stops for the rest of the class.  The gap just keeps getting wider as the fastest thinker is the only one engaging in retrieval practice and those who need it most don't get the time to do it.

Why is this happening?  

Well, for one thing, many education preparation programs don't cover this type of practical classroom technique stuff.  There is a lot of high level philosophy talk about "your why." That's important, don't get me wrong, but how much time does it take you to find it?  There's a lot of Piaget and Maslow.  I guess, if that's your thing, there's nothing wrong with learning it, but I've never thought about either of those mend during an actual teaching day.  There's a lot of talk about "the direction education is heading" even though it never is because it keeps changing direction.  The stuff you need in the daily practice of education is given short time, if any at all.  I moved into a new school building with six science teachers, and not one of us had been taught how to store chemicals safely in the stock room, so you can be certain a small but practical and impactful detail, like wait time, wasn't ever mentioned.  So, teachers don't know.  That is one reason.

Another reason is a thing your brain does, known as "action bias."  If there is activity, your brain reasons that you must be making progress.  You have fallen victim to this if you have ever been sitting at a lengthy red light and made the decision to turn and take a much longer route to your destination rather than sit there for another 30 seconds.  Activity feels more productive, so when we are calling on students quickly, it feels like our classroom is more productive.

The "curse of expertise" may play a role here as well.  Since I know the material well, I could answer this question very quickly, so I assume my students can as well.  It's easy to forget that novices think differently than experts.  It will, of course, take more time for them to even understand the question than it will for a group of experts, much less the amount of time it takes to develop an answer.  That's at play with a lot of recent graduates (you just took a physics course way harder than the one you are teaching) and experienced teachers (your content is second nature to you at this point).  

For me, personally, it was discomfort with silence.  Most of us find more than a couple of seconds of silence awkward, especially when there are people looking at us.  So teachers tend to fill the silence with chatter.  Even when I was getting better with waiting for the kids answers, I was saying more stuff and filling their working memories.  I started keeping a water bottle on the cart next to me so I could take a drink while I was waiting for them to think because it was the only way to shut myself up.  Eventually, I learned to embrace the awkwardness, even taking pride in the fact that I could endure it longer than they could until someone finally answered.

The good news

That was the bad news.  The good news is that this extraordinarily easy to fix.  You literally just wait longer.  The advice given to me to count to three inside my head was good.  I would make it five, though, because most of us count faster than we think we do.  Grab a sip of water; tap five times on your leg, scan the room, whatever you need to do.  Let your students know that you aren't going to call on someone just because they are the first person to raise their hand and that you want them all to have a chance to process their thoughts; they get it and the slower processors appreciate it. 

What time is right?

What is the right amount of wait time?  There's not a clear answer on that.  It largely depends on the complexity of the question and the exposure your students have already had with the content.  If you have been sprinkling retrieval practice questions through out the chapter, and you are asking relatively simple questions on the day before the test, you will not need to wait as long as you would if you are asking a complex question on a new topic.  

What has been observed by researchers, if you want some guidance, is that in classrooms where 3-5 seconds wait time is practiced, there are more correct responses and more variety of responses.  The variety part interests me because some of those answers will be wrong (others will be a variation of right if the question is open), but they are answer that wouldn't even have been proposed with less than three seconds of wait time.  You can't fix misconceptions you don't know they have, so getting a wrong answer from a student is useful to you as a teacher because you have insight into their thinking. 

I don't want you to misread this as an endorsement of a glacial classroom pace. Brisk pacing is a good thing.  Too much idle time is how teachers lose control of their classrooms.  I am only address the time between questions and responses here, not the rest of your lesson.

I know we are at the end of the year here. You may only have a few days or a couple of weeks left, so you might just experiment with this while reviewing for exams.  But keep it in mind when the school year starts next year.  While you are going over your classroom procedures, explain that you value their thinking time and then practice waiting.  The benefits outweigh the awekwardness.