Pearson Education Measurement, which scores more than 40 million student achievement tests each year, announced in February that it would begin using computers to grade student essays. After decades scanning number two pencil dots, the machines have advanced to prose. And the key to that advance is an ingenious process called latent semantic analysis, one of several techniques that researchers and corporations are exploring to cajole machines into understanding the meaning of strings of words instead of just manipulating them.
Illustration by Leo Espinoza
The idea of a computer doing more sophisticated evaluations than tallying up multiple-choice answers has alarmed parents and teachers. If computers still can't figure out that those penis enlargement e-mails in their inboxes are spam, how can they possibly assess the merits of a book report on The Sun Also Rises? As it turns out, the process of training a machine to grade essays is similar to the process of training human graders.
