My first shopping week ever was a marathon. I attended more class hours in five days than I was required to attend in the entire remainder of the semester. I took notes in the classes I shopped, dog-eared the course catalogue most of the way through, sat through entire classes even after they started looking bad and spent a lot of time in the Coop reading books.

Most importantly, though, I asked around. Older friends, friends of older friends, roommates all had advice to give. Any class offered for more than a few years develops a reliable reputation, a strange mix of fact, opinion and hearsay that scales enrollment by factors of ten.

Grow older, grow wiser. Last Shopping Period I had everything down to a science. Master scanner of syllabi and shuffler of classes, I could tell within minutes whether a class was right for me. I'd absorbed enough departmental and extracurricular hearsay to pick classes practically before the lectures began.

But acquiring enough information about a class is rarely a matter of asking more people. Two, three, five opinions or off-hand remarks are usually a representative sample, even for large classes. This is because, I was surprised to find, there's not much dissention.

Ask around about a particular class and people who've never spoken will echo each other's assessments, sometimes even using the same phrases. How is it that 500 people in a lecture class independently come to the conclusion that "the lectures are archaic, the head TF sounds like Marge Simpson, the midterm was hard and the professor is brilliant but incomprehensible"?

Some things are obvious. By junior year, we've all got similar benchmarks. Everybody can tell whether the professor is organized or the reading is superfluous. But the diversity of opinion that exists during shopping week has shrunk, by the end of the semester, to a comfortable homogeneity. Is this a natural process? Or a strange kind of mob psychology?

After the first few sections, territory has been established, the discussions take on a certain character, sleep patterns solidify. Maybe the kid next to you in the baseball jacket complains to you after class and slowly, you notice, class isn't as great as you thought. Maybe your whole tutorial is fascinated by Celtic poetry and you find yourself looking forward weekly meetings despite yourself. Where does the consensus come from? It's all in the details: an off-hand remark that someone makes, a perfect characterization, the collective curve-setting on the midterm. Slowly, the class opinion converges to a mean.

Though the mean's characteristic, it may not be fair. Occasionally I've been surprised to find a required class with a bad reputation quite enjoyable. The problem is not that bad reputations are acquired too hastily and good ones take time--nothing is so easy. Instead it seems that fair and unfair reputations are results of the same process, the same sets of intuition, reaction and details.