I've mentioned Dr. Arthur Benjamin on my blog here and here, so when I started the video portion of Grey Matters, I was bound and determined to find video footage of him somewhere on the web. I'll tell you right now, it isn't easy.

However, I have finally found footage of him on the web! Dr. Benjamin's challenge in the video is to work out the answer to 89573 times 36475 in his head. The complete video itself is broken up into part 1 (above) and part 2. The video itself is somewhat choppy, but it is still watchable.

One thing from the video that may need explanation is the weird words he keeps throwing in, such as “uncle” and “totem” that don't seem to have anything to do with the math problem. These are the word equivalents of various numbers as determined by the use of the Major System of memory. Keeping an image of an “uncle” in your mind is far easier than keeping its equivalent (275) in your head. “Totem”, if you're curious, is helping him to remember the number 113.

There is also a full 20-minute lecture video by Dr. Benjamin available in RealPlayer format. This lecture is about game theory as applied to a game called “Le Her”.

On a related note, this newsletter suggests that video of Dr. Benjamin's “Mathemagics” lecture is available on MSRI site, but I haven't been able to locate it. “Mathemagics” is the name given to the performances and classes that Dr. Benjamin does in which he does complex math in his head.

When I had the honor of meeting Dr. Benjamin at the Magic Castle earlier this month, we talked briefly and had the opportunity to perform for each other. I demonstrated the Knight's Tour for him, allowing him to choose the starting and ending squares. In return, he demonstrated his amazing ability to square two-, three- and four-digit numbers in his head faster than I could do it on a calculator!

Update (6/1/06): I've found another video of Dr. Benjamin multiplying two 5-digit numbers in his head. In this Windows Media movie, he doesn't any mistakes, so you get a better feel for the impressive magnitude of this feat.

Video Formats:
MySpace
RealPlayer
Windows Media