In hockey, the team behind after the first period wins fewer than 33 percent of the games. In baseball, the team losing after three innings wins less than 20 percent of the time.

Basketball is no different. N.C.A.A. teams across all divisions that fall behind in games tend to lose, and more so as the deficit increases. Teams down by 4 at halftime lose about 60 percent of games. Teams down by 8 lose about 80 percent of the time.

But falling behind is not always bad. We analyzed more than 6,000 N.C.A.A. basketball games played in the past four seasons. Surprisingly, the data show that trailing by a little can actually be a good thing.

Take games in which one team is ahead by a point at the half, as Duke was in the 2006 loss to North Carolina. On average, the team with the lead should win more than half of those games. The data, however, show the opposite. The team trailing by a point actually wins more often and, relative to expectation, being slightly behind increases a team’s chance of winning by 5 percent to 7 percent.

The reason is not that teams become cocky, complacent or lazy when they are slightly ahead. And it is not that better teams tend to fall behind at halftime. The results are the same even when taking into account homecourt advantage, the team winning percentages and which team got the ball to start the second half.