(Modern Scantron test sheet; photo by Josh Davis, used under CC license.)

We learned this week that Michael Sokolski, a soldier, engineer, and inventor of the Scantron, died on June 13. Sokolski was an immigrant to the US from Poland, and later an engineer and inventor best known for his work with Scantron. Today, we dig into some Scantron trivia -- please make sure your trivia bubbles are completely filled or the machine may not give you credit.

How Does the Scantron Work?

The original Scantron tests were a form of Optical Mark Recognition (OMR) system, in which a scanning machine beamed light through your test paper and examined the back of the paper, noting which areas were dark using phototubes. The notion was that wherever you'd made a dark mark (using a No. 2 pencil, of course!), the graphite laid down by the pencil would block the light, causing it to bounce off the paper. The machine noted the position of that dark mark detected by the phototubes, compared that position to a master answer key, and tabulated the results. Because of this through-the-paper technique, early Scantron sheets had to be one-sided.

More modern Scantron testing machines use imaging sensors capable of recognizing marks other than those made by No. 2 pencils (hence my Oregon vote-by-mail ballot allowing and even encouraging the use of ink pens on the sheet). These sensors act more like digital cameras, taking a digital picture of the sheet and determining the darkest area. These systems have additional advantages, as their software can (within reason) ignore stray marks and even determine the darkest area in a given region. (You'll know why this is important if you've ever tried to erase your ultra-dark Scantron bubble and left behind a smudgy ghost. Teachers will also be aware of this phenomenon, as those "unscorable" rows had to be examined manually.)

Why a No. 2 Pencil?

Pencils come in different grades depending on the composition of the graphite mixture used within them. The "lead" in a typical pencil is actually graphite powder mixed with clay; the ratio of graphite-to-lead determines the hardness of that lead, which has a lot to do with the darkness of the mark made, as well as how the pencil holds up to repeated use before you have to sharpen it again. The American numbering system is a bit arbitrary, but effectively #2 is moderately soft and #4 is very hard. The #2 pencil (also known as "HB" in the European nomenclature) makes a dark enough mark, but doesn't suffer from the extreme smudging and breakability you can get with harder pencils.

When Scantron systems were first invented, in order to block that light beaming through the paper, the system needed the user to lay down a nice sheet of reflective graphite. The #2 pencil was deemed the right fit for that application -- and it didn't hurt that it was already a very common pencil anyway. You can read way more about pencil grading from Wikipedia, if you're into that kind of thing.

What Made Scantron Special?

OMR systems of various types had been around for decades when Scantron was founded in 1972. Some of the earliest OMR systems (invented in the 1930s and deployed by IBM) used even weirder techniques than the through-the-page light system -- some brushed the page with wires, testing for electrical conductivity (the graphite marks have a markedly different conductivity signature than plain paper). Although Scantron's optical system was patented, the Scantron corporation's other crucial innovation was its business model: by getting inexpensive Scantron test-scoring machines into schools, the company could later make a profit by selling the proprietary test sheets. This is a variant of the classic "razor blade" business model in which you effectively give away the handle but sell the blades, and it worked well for Scantron.

It's important to note that there are lots of players in the standardized test business, so it's likely that many test forms we call "Scantrons" are not the real Scantron-brand item. "Scantron" is one of those trademarked terms like "Xerox" and "Kleenex" that has become partly genericized through common use and overwhelming popularity, despite its valid trademark status.

The College Prep Pro Tip

I flirted with the idea of being a college prep tutor, until I learned about the pay scale involved. But before I gave up on that weekend-long dream, I picked up one pro tip: test-takers should bring slightly blunt pencils to tests. The logic is that if you use a very sharp pencil, it takes longer to fill in the oval completely and you run the risk of breaking the tip; a slightly dulled point gets you to a filled-in oval faster.

If you really do want a sharp pencil, I must refer you to the instant classic How to Sharpen Pencils: A Practical & Theoretical Treatise on the Artisanal Craft of Pencil Sharpening for Writers, Artists, Contractors, Flange Turners, Anglesmiths, & Civil Servants; a book that is, no kidding, the definitive resource on pencil sharpening techniques -- written by David Rees, the world's "Number One No. 2 Pencil Sharpener."

The Scantron Test-Taking Machine

Artist/engineer Christian Croft made a Scantron test-taking robot as part of an art installation. Here's a photo of the machine by Kevin Slavin, used under CC license:

A Crazy Scantron/TRON Crossover

And finally, a Light Cycle scene from TRON done using Scantrons. The animators are clearly not using No. 2 pencils.

What are Your Scantron Memories?

If you're like me, you have a lot of memories of the Scantron from school, including "Christmas-treeing" a test (drawing a Christmas tree or other image using the bubbles, because you knew you'd fail the test anyway), the common lore that "C" is the most common answer on A-D tests, and a bunch of (bogus) notions that things like Chapstick can help you ace a Scantron test. Share your Scantron memories in the comments.