Reportedly, Robo-Graders -- computers capable of grading 16,000 essays in 20 seconds -- perform as well as human beings, who are expected to spend no more than two to three minutes per essay. The automated efficiency is appealing, but speed comes with a catch: you can write a terrible paper, filled with incorrect facts and get a better mark than a paper that actually sticks to history.

Mr. Perelman found that e-Rater prefers long essays. A 716-word essay he wrote that was padded with more than a dozen nonsensical sentences received a top score of 6; a well-argued, well-written essay of 567 words was scored a 5.

An automated reader can count, he said, so it can set parameters for the number of words in a good sentence and the number of sentences in a good paragraph. "Once you understand e-Rater's biases," he said, "it's not hard to raise your test score."

E-Rater, he said, does not like short sentences.

Or short paragraphs.

Or sentences that begin with "or." And sentences that start with "and." Nor sentence fragments.

However, he said, e-Rater likes connectors, like "however," which serve as programming proxies for complex thinking. Moreover, "moreover" is good, too.

Gargantuan words are indemnified because e-Rater interprets them as a sign of lexical complexity. "Whenever possible," Mr. Perelman advises, "use a big word. 'Egregious' is better than 'bad.' "