Take a simple study on pens led by Avni Shah and George Wolford, psychologist at Duke University and Dartmouth College, respectively. The scientists found twenty different pen options, all of which cost between $1.89 and $2.39 and contained black ink. The subjects were told that the pens cost about $2, but that they could purchase any of them for a special discounted rate of $1.
Here’s where things get interesting. At first glance, offering people more pens might seem like a good thing, since they can find the pen that best suits their needs. Some people like ballpoint pens, others prefer roller-balls, or just care about the texture of the grip. Sure enough, offering people more pens led to a higher percentage of people buying pens, at least at first. When only two pens were offered, 40 percent of students bought one. However, when there were ten pens to consider, 90 percent of people found one they liked enough to buy.
But now comes the inverted U-curve—when more than ten pens were offered, people became much less willing to choose any pen at all. The drop-off was steep: when there were sixteen different pens to choose from, only 30 percent of subjects bought one.