People naturally partition the world into round numbers. We say it takes 30 minutes to get to work and ask where we see ourselves in five years. Rain Man knows when 246 toothpicks fall on the floor, but most of us would hazard a guess of couple hundred (and a clean 250 came in the box). High school students are much more likely to retake the SATs when their scores fall just below a double-zero ending. Baseball players hitting .300—the threshold for a fine season—often remove themselves from a final at-bat to avoid dropping to .299.
Nowhere is this tendency toward round numbers more prevalent than on lists, and nowhere are lists more prevalent than on the Internet. Recently, marketing scholars Mathew S. Isaac of Seattle University and Robert M. Schindler of Rutgers University conducted a simple little test of this web norm. They searched the term "top [number]" in Google using all numbers 1 through 100. Those ending in zero dominated, followed closely by those ending in five.
This affection for round-numbered lists might seem irrelevant, but Isaac and Schindler believe it biases the very way we perceive certain items on these lists. In an upcoming issue of the Journal of Consumer Research, they argue that people exhibit a so-called "top 10 effect": lumping things into round-number groups and viewing everything outside them as inferior. So the difference between items ranked No. 10 and No. 11 feels enormous and significant, even if it's actually quite minimal or unknown.
"Our own experiences sort of led to this impression that if it's not in the top 10, then it's in the next category," Schindler tells Co.Design. "The overall idea is that numbers generally are considered to be equidistant, but subjectively they're not."
Isaac and Schindler tested the top 10 effect in a series of experiments. For one study, they showed 205 test participants a fictional list of students in a math class ranked in order of their performance on a recent exam. In fact, the researchers devised five different lists, and placed one name—Charles Pipp—in various spots in each. Depending on the list, test participants found Pipp ranked No. 8, 9, 10, 11, or 12.
After reviewing the list, test participants evaluated Pipp's individual math skills on a scale ranging from weak to strong, then evaluated his skills relative to the student ranked immediately above him. In both cases, Pipp's perceived skills suffered most when he was ranked 11th. The relative ratings were especially telling: of all the comparisons between Pipp and the student ahead of him, the greatest evaluative gap occurred when he was ranked 11th and the other student 10th.
In another study, Isaac and Schindler demonstrated that the top 10 effect infects behavior outside the lab, too. They compiled data on more than 484,000 people who took the GMAT over a three-year period, and also documented business school rankings in U.S. News and World Report over this same stretch. GMAT test takers submit their scores to five pre-selected business schools, and the researchers wondered whether the U.S. News rankings might have influenced those decisions.
For the most part, the rankings had no statistical effect on where scores were sent. There was no connection between test-taker submissions and the magnitude of a school's shift (its change in ranking) or a shift within a 10-number window (say, from eighth to seventh). All told, Isaac and Schindler found only one change that predicted how many score reports were sent to a school: when the school moved into a new round-number rank category, as from 11th to 10th.
Of course, circumstance and context can help conquer the top 10 effect and its round-number cousins. In another experiment, Isaac and Schindler found that when test participants were exposed to a sharp-numbered list—like a Top 19—their perceived gap between 10 and 11 diminished. The business lessons for the Number 11s of the world is pretty clear: crack the Top 10 at whatever the cost or change the reference point to Top 12.
Schindler himself fell victim to the round-number bias when contacted by Co.Design for this piece, saying he couldn't talk now but would call back in an even 20 minutes. Recognizing that irony later, he suggested a very simple reason for this habit and the top 10 effect that comes with it: categorizing things helps us process a massive amount of information quickly. "It's absolutely characteristic of people, when they have to produce numbers, to produce round numbers," he says. "They're just so much easier. You wouldn't know where to start."