Tuesday, December 30, 2014

Legibility and Pseudoteaching

Cross-posted from Teaching Is . . .

One of my favorite parts of the 1989 movie "Look Who's Talking" is when the infant tries to figure out how to drive a car. You just put the little stick into the hole, move your foot back and forth, and move the big circle around. We've all seen it done, how hard can it be?

We've all seen what teachers do, too, thanks to years of schooling. As with the car-driving baby, our picture of what teachers do was formed when we were children, but that doesn't stop us from thinking that we know what teaching is. How hard can it be? We know what it looks like, or, more to the point of this blog post, we know it when we see it. We know what it should look like.

Legibility
I first encountered the concept of legibility in a blog post by Venkatesh Rao in his blog Ribbonfarm. The concept was originally expressed in a book by James C. Scott called Seeing Like a State: How Certain Schemes to Improve the Human Condition Have Failed. I'll quote Rao's excellent summary of how the failure comes about:
Here is the recipe:
  • Look at a complex and confusing reality, such as the social dynamics of an old city
  • Fail to understand all the subtleties of how the complex reality works
  • Attribute that failure to the irrationality of what you are looking at, rather than your own limitations
  • Come up with an idealized blank-slate vision of what that reality ought to look like
  • Argue that the relative simplicity and platonic orderliness of the vision represents rationality
  • Use authoritarian power to impose that vision, by demolishing the old reality if necessary
  • Watch your rational Utopia fail horribly
The big mistake in this pattern of failure is projecting your subjective lack of comprehension onto the object you are looking at, as "irrationality." We make this mistake because we are tempted by a desire for legibility.

The Illegibility of Teaching
I read this article just as I had started teaching again after a 25-year hiatus. I was being reminded of what I love about teaching and what annoys me about teaching. I realized that I had found the perfect concept for describing what annoys me: though everyone thinks they know what teaching is, teaching is largely illegible, even to other education professionals.

This illegibility is never attributed to the observer's ignorance. It is always seen as a sign of chaos in need of order. The preferred order is for the classroom and the teachers and the students to have a certain "look." This might mean signs of "discipline," an atmosphere of "quiet, steady diligence," or the appearance of "motivated" students led by an "engaging" teacher. Whatever signifies legible order for the observer is the ideal, even if that order results in no actual learning. One of my school principals insisted that he could poke his head into a classroom and tell at a glance if a teacher was "getting it done." Legibility is more important than education. More to the point, education is to be found in the legibility of the enterprise rather than the results.

I don't mean to complain, I'm just trying to understand. Certainly there are bureaucratic, political, and commercial forces pushing education in directions that suit their various non-educational agendas. This happens in all spheres of life, and it is easy to spot and understand. What bothers me is when intelligent and well-intentioned people confuse complexity with irrationality. It is very difficult to correct this misperception.

*   *   *

Pseudoteaching
This brings me to a related concept called pseudoteaching. This concept is defined by Frank Noschese in his blog Action-Reaction:
The key idea of pseudoteaching is that it looks like good teaching. In class, students feel like they are learning, and any observer who saw a teacher in the middle of pseudoteaching would feel like he’s watching a great lesson. The only problem is, very little learning is taking place.

What is so seductive about pseudoteaching is its legibility, not its effectiveness. Everybody is happy; the teacher feels great, the students know exactly what is expected of them, any visitor to the classroom is suitably impressed. What makes everyone happy is that no-one's misconceptions or misperceptions are being seriously challenged. And that's also why so little learning is taking place.

Here we have a mutually-agreed-upon legibility, what Timothy Slater has called the Hidden Contract.  Inasmuch as we all agree that a classroom should look like this, and as long as the classroom in fact does look like this, then everyone is comforted by the apparent order (or apparent lack of chaos).

One of the guest pseudoteaching entries in Action-Reaction is Khan Academy and the Effectiveness of Science Videos by Derek Muller. He describes the phenomenon of student satisfaction with pseudoteaching this way:
Research has shown that these types of videos may be positively received by students. They feel like they are learning and become more confident in their answers, but tests reveal they haven’t learned anything.
And what is meant by "not learning anything?"
Students have existing ideas about scientific phenomena before viewing a video. If the video presents scientific concepts in a clear, well illustrated way, students believe they are learning but they do not engage with the media on a deep enough level to realize that what is presented differs from their prior knowledge.
(Read more about Muller's research here: What Puts the Pseudo in Pseudoteaching?)

Rationalizing Teaching
One way to "rationalize" teaching so it is more legible is to simplify the end result. As Rao points out,
. . . a reality that serves many purposes presents itself as illegible to a vision informed by a singular purpose. Any elements that are non-functional with respect to the singular purpose tend to confuse, and are therefore eliminated during the attempt to "rationalize."
If the end result of teaching is reduced to, say, students passing a certain test, then teaching itself can be rationalized and made quite efficient and effective. The IQ test, for instance, was originally developed as an expedient military management tool. It has become the very definition of intelligence in the minds of many, reducing a complex human trait to a single legible number.

There is a kind of learning called procedural learning. Procedural learning is the first step toward acquiring a skill, and it usually involves practicing a procedure, recipe, or algorithm until it can be performed correctly and automatically. It is a favorite goal for teaching because the path to successful learning is quite straightforward. Procedures, even complex ones, are ultimately rational, and thus legible. A classroom that is focused on procedural learning is also legible.

There are those who would like to define education as being simply this; learning how to successfully execute a procedure. I, for one, would prefer a definition that encompasses a great deal more. As a physics teacher I value rational thinking, the interplay of perception and concept, creative problem-solving, and the exercise of judgement when executing procedures. I also value observing, dreaming, and play. Can any of these preferences of mine be successfully taught? Should I even try? When does the goal become so complex that it becomes illegible to me, and I fall into the traps of rationalizing or pseudoteaching?

Maybe I could define education as simply this; learning how to convert an illegibly complex experience into a legible one without falsely rationalizing it.

Saturday, November 22, 2014

Adding WOWSlider to Blogger

Sorry, as of August 31st 2016 Google Drive no longer hosts HTML files. You can still store an HTML file on Drive, but if you link to it, you will be prompted to download the file. It will not be rendered in your browser.

Read my post here about a quick alternative called WWW Drive. You can still store your files using the directions below in Google Drive, with the same folder structure. You will have to revert the link changes back to what WOWSlider originally generated. As long as your folder is public, WWW Drive will find it and give you an alternative link to your HTML file (or just to your folder - WWW Drive will find and host the index.html file automatically). Use the link generated by WWW Drive in your iframe tag.

Alternatively you can find a host (I am using Google Cloud), transfer your files there, and revert your link changes (if you made them) back to what WOWSlider generated.

Here are my new sliders on my Portfolio page: http://billcalhounteacher.blogspot.com/p/portfolio.html.

Click HERE if you would like to remove the strikethrough and read the original directions.


I've been wanting to add a WOWSlider slideshow to my blog. WOWSlider is a little application that creates many different kinds of very cool sliders. The application generates a collection of files:
  • an engine folder which holds the CSS, JavaScript, and small images and icons for the slider functions;
  • a data folder which holds the slide images, along with thumbnail and tooltip images;
  • and finally the HTML document called index.html.

The WOWSlider website has incorrect information about adding a slider to a Blogspot post. The main difficulty is that the two generated folders need to be located somewhere on the Web to be accessed by your browser through the HTML file. If you have a website hosted on a server somewhere, you can add the folders there, and that is what some people have done successfully.

Hosting the folders and files on Drive

I don't have a hosted website, but I do have Google Drive, which is capable of hosting files for websites, so here is what I did.
  • In my Drive account (which you automatically have if you have a Google account), I created a folder that I called Slider1.
  • I made sure that the folder was shared (public on the Web - anyone can find and view).
  • Then in it I re-created the folder structure generated by WOWSlider: in my case it was a folder called engine1 and a folder called data1.
  • Within data1 I created the three folders that WOWSlider had generated: images, thumbnails, and tooltips.
  • Then I uploaded all the WOWSlider files (but not index.html yet!) from my desktop to the appropriate folders on Drive.
This last step is easily done, depending on your browser. Some browser versions let you drag-and-drop a whole list of files at once. Some browsers can upload the whole folder structure with its files all at once!

I navigated back to the top folder, the one I called Slider1, and selected it. Then I clicked the Link icon and copied the link. I pasted it into a text editor on my computer (Notepad++ rocks!). Mine looked like this:
https://drive.google.com/open?id=0B49MqzTRp5q6NEF5NEhsX09NckE&authuser=0
Note the "id=" part. That's the id of the main folder (minus the "&authuser=0" part). I edited the link so it looked like this:
https://googledrive.com/host/0B49MqzTRp5q6NEF5NEhsX09NckE/
(You can click on this link to see my test slider.)
I used my editor to open the index.html file that WOWSlider generated. There are several links in there. All I needed to do was add the "https://googledrive.com/host/0B49MqzTRp5q6NEF5NEhsX09NckE/" to the front of each link URL. So a link that looked like this:
src="engine1/jquery.js"
now looked like this:
src="https://googledrive.com/host/0B49MqzTRp5q6NEF5NEhsX09NckE/engine1/jquery.js"
My slider had 7 images, so there were 7 links to images, 7 more links to tooltip images, 2 links in the head section (to CSS and JS files), and 2 final links toward the end of the file. (This was very quick work - use the replace function of your editor.) Your file will be different, so check carefully.

Then I uploaded this adjusted file to Drive, within the Slider1 folder.

Adapting Blogger to display the slider

There is a way to paste lines of code from index.html into your blog template and into your blog post or page. I tried it, and the results weren't very good. The best approach for me was to put the slider into an Iframe in my post or page. An Iframe is a window into which your slider will be placed inside the body of your post.

I created a new Page (you could create a new Post as well) and typed the following (you might have to click the HTML button first):
<iframe src="https://googledrive.com/host/0B49MqzTRp5q6NEF5NEhsX09NckE/index.html" style="height:350px;width:585px;margin-left:-20px;overflow:hidden;border:none;" scrolling="no"></iframe>
Notice that the Iframe source (src=) is the URL for my index.html file in Google Drive. You'll have to put your own URL in. You can mess with the height and width and margin. It is redundant to have scrolling = "no" and "overflow:hidden;" but until all browsers finish the transition to HTML5, it's the most reliable way to eliminate the scroll bars.

Now you can build the rest of your post around the Iframe, using style options like "float:left;" or "border:5px solid red;" in the Iframe. You treat the Iframe very much like an image. WOWSlider also generated a file called iframe_index.html, and you could look in there for more options.

(Check out the sliders on my Portfolio page: http://billcalhounteacher.blogspot.com/p/portfolio.html)

Sunday, November 16, 2014

Physics Toys, Games, and e-Learning

Physics educators have been developing and employing digital simulations for decades. Over time these simulations have evolved into sophisticated toys and games, and have become a regular part of the physics teacher’s repertoire of instructional resources. This article is a personal reflection that takes a look at these toys and games from my own experience as a high-school physics teacher.

What is a Toy?

Here is one example of a definition. This is quoted from a blog post by Beat Schwendimann (2014), a Swiss researcher in learning and visual representation:
The main difference between toys, games and puzzles is the amount of constraint and authorship the player has over the experience. The more authorship the player has over a puzzle, the more it becomes like a toy. The more the player is the actor following the strict guides of the toy, the more the toy becomes like a puzzle. . . Changing the role of the player changes the experience: When you add a goal to toys it will become a game.
In a sense, a game comprises several toys, all working together in a particular way to achieve the goal of the game.

The equations of physics are effectively models of how the world works. When these models are put to work in some fashion, you have a simulation. Digital simulations can be toys, puzzles, or games.

A Classic Digital Toy

Probably the most well-known physics toy is Line Rider. Often referred to as a game (and derided as such), it is a simple simulation of an object sliding along a surface with little friction. The fun of this toy is that you draw the surface however you like (the “line”), and when you hit the play button a cartoon man on a sled (the “rider”) slides on the line as if it were covered with snow. The rider often crashes, or is left tumbling through space endlessly. There isn’t a built-in goal, but users often create a goal of controlling the path of the rider in some way. Paths can be deleted or saved. Some very elaborate paths have been recorded and presented publicly on YouTube. A copy of the game is embedded below.



How Line Rider is Used in the Classroom

A student simply playing with Line Rider discovers quickly that the rider does not necessarily follow the path. He or she immediately catches on and will try again, sometimes over and over, manipulating the line until control of the rider is achieved. Then the student might adopt another mode of use, designing specific paths to see what will happen, and eventually designing paths to carefully control what happens.

This kind of intrinsic motivation is quite engaging, and has pedagogical uses, however minor. To increase the pedagogical value, the teacher needs to construct some kind of scaffolding because the toy does not have any further intrinsic scaffolding. The physics concepts evident in Line Rider are gravity, free-fall, potential and kinetic energy, and friction. All of these concepts are accurately modeled in Line Rider, but not in overt ways, hence the need for scaffolding and guidance if this toy is to become an educational tool.

How Line Rider Fails as a Physics Toy

The primary failure of a digital toy or game is when the model underlying the simulation violates the laws of physics. This is surprisingly common. Our perception of certain experiences sometimes differs from the physical model, and simulations, especially commercial ones, will tend toward the perception rather than the model.

How big is the full moon? Making a circle with your fingers and holding your arm out, estimate the size of the moon’s disk. Now hold your thumb up, straighten your arm, and look at your thumbnail. The full moon has a diameter about half the width of your thumbnail. I know, you don’t believe it, but it’s true. No game designer or animator will ever make the moon that small because it will not be believable.

In a similar way, we perceive any acceleration as being much greater than it actually is. If you examine Line Rider, you will see that there is a control with a red box under it. This is a later addition to Line Rider. When you click on the tool and draw, it creates an “acceleration” line that patently violates the laws of physics. It is there because the rider does not move quickly enough to satisfy some users. When my students discover this tool they enthusiastically adopt it. With proper (and elaborate) scaffolding, a lesson can be made to help students understand the violation. Otherwise, Line Rider fails in this regard as an educational physics tool.

How Line Rider’s Failure Could Become a Feature

The PhET Interactive Simulations program, hosted by the University of Colorado Boulder, has numerous simulations that are quite popular with teachers. Their research is extensive, and includes such topics as intrinsic scaffolding (scaffolding built into the simulations) and student agency and ownership of the learning process (see, for example, Podolefsky, Moore, and Perkins, 2013). Here is their design strategy, quoted from their website (http://phet.colorado.edu/en/about):
To help students engage in science and mathematics through inquiry, PhET simulations are developed using the following design principles:
  • Encourage scientific inquiry
  • Provide interactivity
  • Make the invisible visible
  • Show visual mental models
  • Include multiple representations (e.g., object motion, graphs, numbers, etc.)
  • Use real-world connections
  • Give users implicit guidance (e.g., by limiting controls) in productive exploration
  • Create a simulation that can be flexibly used in many educational situations

If I were to use this design strategy to redesign Line Rider, I would add at least two tools to the toy: a way to adjust the friction of the surface, and a way to adjust the acceleration of gravity. Both of these adjustments would have numerical or descriptive indicators so users would know exactly how much and what kind of adjustment they are making. This adaptation would preserve (or possibly enhance) the scaffolding, yet still allow the user to make the game as exciting (or dull) as the user wishes. Such adjustments could include an option that would be physically impossible (such as anti-gravity). This violation of physics would be chosen by a student with full knowledge, thus obviating the need for further scaffolding to cover up the toy’s apparent failure.


References

Schwendimann, B. (2014). What is the difference between a toy, a game, a puzzle, and a sport? Proto-Knowledge (blog). Retrieved 16 Nov 2014 from http://proto-knowledge.blogspot.com/2010/12/what-is-difference-between-toy-and-game.html
Podolefsky, N., Moore, E., Perkins, K. (2013). Implicit scaffolding in interactive simulations: Design strategies to support multiple educational goals. (arXiv Reference No.: 1306.6544. Retrieved 16 Nov 2014 from http://arxiv.org/ftp/arxiv/papers/1306/1306.6544.pdf

Sunday, October 19, 2014

How Well Do MOOC's Teach?

The short answer is - they don't! Sebastian Thrun, the founder of Udacity, was upset and puzzled to find that only 4% of students who paid to take a course actually completed it. The first time I heard this, I immediately knew why. It's the same reason why the publishing industry in the US can sell 60 million cookbooks a year but people still find it difficult to cook at home on a regular basis. Instructional materials, whether books or MOOC's, do not teach themselves; it's the students working from these instructional materials who are teaching themselves. Because it can be difficult to teach yourself something, students rely on teachers as well as instructional materials. Teachers teach.

I was thus immediately drawn to a blog post entitled "MOOCs are a fundamental misperception of how teaching works" (link here), by Mark Guzdial (January 4, 2013). He makes three points:
  • The main activity of a higher-education teacher is not to lecture.
  • A teacher is an expert at teaching the topic, and the teaching is dependent on the domain.
  • The job of the teacher is to educate, not filter, and that includes motivating students.

Guzdial spells out clearly why a MOOC does not accomplish these three points, and thus is not teaching as properly understood.

Guzdial's argument, by the way, is not an argument against MOOC's, it's an argument against thinking that MOOC's can replace teachers. Instructional materials are vital to learning, but they do not, in themselves, teach. Without a teacher, a student is left to teach himself - a risky enterprise.

Social Media-phobe

I'm not a big social media guy. I don't see the Internet as a place for hanging out or socializing, activities I prefer to do with actual people in real time. But I'm beginning to appreciate how these social tools, the so-called Web 2.0, are capable of so much more than online partying.

I have an assignment to create a Networked Learning Space, and I have been thinking of how to set it up. There needs to be a hub of some sort at the core of this NLS, but which social tool would be best for my purposes? I have been checking out various LMS apps (Canvas, Edmodo) and existing network spaces (edWeb, Google+), but the answer has been in front of me all the time.

I don't have a Facebook account (I know, I know, it's a long story . . .), but my band does. The account is maintained by our musical director, and of course I visit it all the time, and send him things to post. It dawned on me that the band page is not like a regular Facebook page, so I did a bit of research and discovered that Facebook pages are quite different from Facebook profiles. I'll need a FB profile to create a page, but I can ignore that if I want and use the FB page for my NLS. Cool! Plus I'll be able to be another editor of my band's page, so I can help out.

Here's the link to my band's page - the Marching Milkman Band!



Satellite Blogging

Probably the most amazing Twitter account I have ever seen is the account of an inanimate object - a space satellite, to be specific. This satellite (and its companion satellite) tweets its exploits on a daily basis. The satellite belongs to the European Space Agency (ESA), which itself has quite a sophisticated web presence (their blog is here), and it has been in space for a decade.
The Rosetta spacecraft was designed to intercept a comet. It has spent almost all of the decade traveling out to the comet and lining itself up to join the comet in its journey toward the Sun. As I write it is in orbit around the comet and preparing to launch a small lander that will hopefully not bounce off the comet or crash into it, but instead spear itself into the surface and begin doing its science.

It's a very cute Twitter account, written as if the spacecraft itself was writing the tweets, and linking to a host of online resources - Twitter, Facebook, YouTube, blogs, websites, and webcasts. I've been an astronomy buff since I was 10 years old, so when Rosetta caught up with the comet finally this summer, I was quite excited. I'm always looking for a way to add astronomy to my physics classes.

Whenever I have a free 5 minutes or so in class, I put the Twitter feed up on the Smartboard so we can all have a look. The students feel my enthusiasm, and get pretty caught up in the excitement. They also think it's cool that I'm using Twitter and YouTube in the class. I've been doing this since the first week of school.

Sunday, September 28, 2014

Sheer Genius

Years ago I was visiting a friend whose son was sitting at a computer nearby doing his homework. I could tell that his mom was convinced that doing homework on a computer, whatever she thought that meant, was going to result in her son being smarter, or a better student, or something. I watched him out of the corner of my eye. He had a list of questions he needed to answer, and he certainly was smart enough to have figured out his technique - type each question verbatim into the Google search box, then write down whatever appeared as the first entry on the results page. He was done in 10 minutes - sheer genius!

I mention this because it's all there - the disruptive technology, the hype about computers, a teacher who probably had no idea that the answers were obtained this way, a student who never bothered to visit a single webpage other than Google.

So I think about not asking my own students questions that can be answered so simply, and I think about how to help them navigate the sea of online information. I also try to remember that I have no idea what information technology will look like years from now, but some concepts about acquiring and using information will forever be true.

Teaching or Filtering?

I have taught physics to children of all ages, from 3rd graders to high-school seniors.  Some people find this improbable - of course, whatever is being taught to, say, middle-schoolers in the name of physics must not be real physics.  Why not? I ask.  Well real physics is complicated and requires advanced math, like calculus, they say.

But aren't there concepts in physics that can be conveyed to younger students?

Concepts are fine, but physics isn't real without the math.

But math taught to middle-schoolers is real math, isn't it?

Yes, but that's different.  These students will take math for many years, getting better and better at it.

So there is no point in introducing students to the basic ideas of physics?

Well, why bother?  You won't be able to say that they really KNOW physics.

But I'm not trying to claim that they will become professional physicists through my class.  I just want them to have experienced how physicists see and think about the world.

Unless they plan on pursuing science in college, there isn't any point.  And if your students get good grades in your class, you will, in fact, be claiming that they KNOW physics.

I'll be claiming that they know what I've asked them to learn, basic physics concepts.

And that will be a misleading claim.  Everyone knows that only the smartest students can really learn physics.


That last notion is a back-handed compliment, I guess.  I certainly did learn physics in high school and college, so apparently I numbered among the "smartest" students.  As a teacher, though, I reject the notion, and if I'm so smart, why is my assertion about the ability to teach physics to everyone not accepted?

The answer lies in deeply-held but foggy notions about "smartness," and what it means to know something, about the capacity to both teach and learn.  Ultimately, the question needs to be asked; what are we doing in our schools, are we teaching or are we filtering?  Which function does our society most want from its schools?

As a high school physics student, I was the product of filtering.  Physics was a high-school course that only the brightest students were allowed to take.  The filtering process began in middle-school with students being grouped into divisions based on academic ability.  From that point on, expectations both low and high became reality.  In high school we were separated into tracks that were to guide us to the appropriate socio-economic outcome.  The requirements for taking physics were steep - we were the final filtrate, the ultimate refinement.

I completely understand my interlocutor above.  There exists a sense that physics is an elite study.  I had a friend who insisted that I must understand the whole universe if I understand physics.  But is it elite only because the bar to entry is set so high?  Is physics, or anything else for that matter, so fundamentally difficult to understand that a teacher can only throw his hands in the air in despair?  If so, then we are left with filtering - separating the wheat from the chaff, the elite from the common, the deserving from the disqualified, the good from the bad, the smart from the stupid.  Filtering may be an understandable, even natural, practice, but imagine what good, effective teaching could do.

What's so Wrong With PowerPoint?

I was looking for a social media site where I could share presentations, and a colleague suggested SlideShare. It's a very nice looking site, and it seems to serve a large community. I haven't explored the site thoroughly, but I have viewed a number of the slideshows, and they are either PowerPoint-type or PDF presentations.

I am often bored or even annoyed by most PowerPoint (PP) presentations. In response to my colleague, though, I pointed out that I wasn't sure if the problem with PP was the program itself or just how it is used. As I put it, "I'm no Powerpoint fan, but I know it's because so many PP presentations are terrible! No CARP awareness [see below], no narrative or even logical arc. I rarely use it, so I haven't learned the ins and outs. I did meet a chemistry teacher from Korea who had done some amazing things with PP, though."

Heaven knows we have all suffered through poorly designed PP presentations. Another colleague sent me a link to an essay by Edward R Tufte (2006) entitled "The Cognitive Style of PowerPoint." He makes a strenuous argument against the underlying approach of PP, explaining how that approach corrupts the presentation of analytical data. PP is inherently flawed - it is PP's fault!

On the other hand, there is a well-known approach to the design of visual presentations based on four principles: Contrast, Arrangement, Repetition, and Proximity (or CARP, for short). These are the principles often violated in PP presentations, and for which PP can't be faulted (though Tufte argues that PP is almost designed to enable these violations).

I already use a presentation tool every day in my classes - SmartNotebook, which is part of the software suite that accompanies Smartboards. I don't think I'm doing anything with SmartNotebook that I couldn't do with PP, but it feels more intuitive and responsive to what I'm doing in my classroom. PP always feels static (though I still think about that chemistry teacher from Korea!)

I haven't yet played with Prezi - I guess I should try, because it seems to be a good alternative to PP. I also want to play with the screen-capture tool Jing, and see if I can record presentations and share them on YouTube. Prezi and SmartNotebook also have archives for sharing presentations.

Related links:

E R Tufte's essay (PDF)
Here's
a Prezi presentation about CARP!
Ironically enough, a SlideShare presentation on "Death by PowerPoint."
An article in PC World entitled "Anything but PowerPoint." (The main complaint here seems to be that PP presentations are boring. Most of the alternatives offered are just variations on PP.)

References:

Tufte, E. R. (2006). The Cognitive Style of PowerPoint: Pitching Out Corrupts Within, (2nd ed.) Cheshire, CT: Graphics Press.