Before humans stored memories as zeroes und ones, we turned to digital devices of another kind — preserving knowledge on the surface of fingers and palms.
When Mogao Caves was uncovered in 1900, an aging drawing was lifted from a trove of religious manuscripts. The drawing illustrates a mnemonic (助记符号) system, a way of projecting knowledge onto the hands so it can be studied, memorized, and stored in a pocket. Around the same time this mnemonic was made, a monk named Bede halfway around the world was developing a different system of manual knowledge. These two systems are perhaps the earliest examples of manual mnemonics.
Beginning roughly twelve hundred years ago, we started using the hand itself as a portable (便携的) place of knowledge, a place to store whatever tended to slip our mental grasp. The hand became an all-purpose memory machine.
In different times and places, hands provided mnemonic maps of sound. As early as the thirteenth century, Chinese scholars were projecting syllable charts (音节图表) onto the palms and fingers. The so-called "Guidonian hand" owes its name to the eleventh-century Italian music teacher, Guido d'Arezzo. Arranging the different pitches in a scale onto the joints, he developed this technique to help students learn "unheard melody most easily and correctly". Other thinkers in Europe, perhaps inspired by Guido, developed systems for learning the sounds of language.
Then questions arise. First, what makes the hand so popular as a mnemonic prop? A large part of the answer, surely, involves portability. The hands are always, well, ready to hand. A further advantage stems from how hand mnemonics offer both visual and kinesthetic (动觉的) routes to memory: They are both seen and felt.
It's also hard to determine when and why hand mnemonics faded out. Hand mnemonics are still used to teach the "right-hand rule" in physics classrooms and remain especially popular in medicine. Today we increasingly store our "thoughts" in virtual realms (领域), but we sometimes still reach for that original "digital" repository (存储库) in our pockets.
