Tuesday, March 2, 2010

Channel Capacity or the Limits of the Human Brain

One of my undergraduate professors taught a class on organizational behavior. A former CEO and something of a guru on the inner workings of corporate structure and relationships, his course took roots in psychology and cognitive science. One of the concepts he introduced to us was that of channel capacity. Companies are best served to limit the size of each of their units to fewer than 150, as humans just can't keep track of the relationships between a group larger than that. In addition to a social channel capacity, humans also have an intellectual channel capacity and are limited in their ability to keep more than seven items simultaneously in their RAM. It's why phone numbers are (used to be) seven digits.

Preparing for an anatomy practical requires understanding, either explicitly or implicitly, the concept of channel capacity. The practical exam last week, the end of my second quarter, covered face, neck, thorax, and abdomen. The list of structures held us accountable for about 350 named items to identify on sight based on structural relationships and appearance. Identifying any individual item on the list requires knowing at least three or four relationships in order to make identification possible. Let’s take the thyrocervical trunk of the subclavian artery as an example. I know that the thyrocervical trunk is the third branch of the subclavian, and the second that branches upward. I know that it gives off the suprascapular artery, the transverse cervical artery, and the inferior thyroid artery. I know that the suprascapular and transverse cervical arteries split off in front of the anterior scalene muscle in the shape of a V, and that the thyrocervical trunk branches near the downward aiming internal thoracic artery. I know what arteries generally look like in the body (they hold shape, unlike veins), and I know where the subclavian artery sits. Also, structures vary slightly from body to body and the dissection usually differs as well. We’re not given a word bank, so we have to pull the names out of our memory only. Lab practicals cover 75 items. Walking through the room from body to body is like going back home from college after a few years, showing up to synagogue, and trying to put a name to all the faces. Except the people at synagogue are generally more alive and less rotten. Generally.

The ability to keep fewer than ten items in your RAM simultaneously plays in as well. Arteries branch like crazy. Memorizing the branches works best in clusters. As opposed to memorizing the subclavian artery and all of it’s branches and their branches and their branches and so on, it’s best to memorize the branches of the subclavian (there’s a mnemonic for that), the branches of the external carotid artery (there’s a mnemonic for that), and then the branches of those branches. I’m very visual, so it’s almost like looking at Google Maps; I can view the whole image at a low resolution or zoom in on individual regions one at a time. The human brain is a ridiculous piece of hardware.

*I'm having trouble recalling the exact number (on account of the subclavian artery). Gladwell says it's 150, but I distinctly remember it to be 300, and I'm struggling to come up with sourcing. Until I find proof either way, my point remains the same.