Few ideas from psychology have travelled as far beyond the laboratory as the…

Few ideas from psychology have travelled as far beyond the laboratory as the notion that too much choice is bad for us. Its best-known source is a study published in 2000 by the psychologists Sheena Iyengar and Mark Lepper. At different times, shoppers at an upmarket supermarket in California were offered a tasting table with either 24 or 6 kinds of jam. The larger display attracted more attention: 60 percent of passing shoppers stopped at it, compared with 40 percent for the smaller one. Yet when it came to buying, the pattern reversed dramatically. Around 30 percent of those who visited the small display went on to buy a jar, while only 3 percent of those who had faced 24 options did so.

The finding seemed to capture something people already suspected about modern life. In 2004 the psychologist Barry Schwartz brought it to a mass audience in his book The Paradox of Choice, arguing that an abundance of options, far from making us freer, often leaves us anxious, slow to decide and less satisfied with whatever we eventually choose. If we pick one of 24 jams, the argument goes, we are haunted by the thought that one of the other 23 might have been better.

The idea proved irresistible to businesses and policymakers alike. Retailers cut the number of products on their shelves, and advisers urged governments to simplify everything from pension plans to health insurance. Choice overload had become, in the eyes of many, an established fact.

Science, however, rarely moves in straight lines. As other researchers tried to repeat the jam study using different products and settings, the results proved stubbornly inconsistent. Some found the same effect; others found none at all; a few even found that more choice made people more likely to buy. In 2010, a team led by Benjamin Scheibehenne combined the results of 50 experiments and reached a striking conclusion: on average, the effect of the number of options on people's decisions was close to zero.

This does not mean the original study was wrong. Rather, it suggests that choice overload is real but appears only under certain conditions. A later review, published in 2015, identified some of them. People are more likely to be overwhelmed when the options are difficult to compare, when they have no clear idea of what they want, when the decision itself feels complex, or when they simply want to get it over with quickly. A wine expert faced with a hundred bottles may enjoy the challenge; a newcomer, unsure what distinguishes one bottle from another, may walk away empty-handed.

The story of the jam study is therefore a useful lesson in how scientific ideas become popular. A single, memorable experiment can shape public thinking for decades, while the more complicated picture that emerges later rarely makes headlines. For anyone designing a menu, a website or a public service, the lesson is not that fewer options are always better, but that the way choices are presented may matter as much as how many there are.