Merchants are hard at work these days trying to influence customer choice. Here’s some new research that might help. Specifically, these researchers looked at how assortment size influences whether shoppers choose indulgent or practical products.

In one experiment, two groups of participants were shown pictures of ice cream, and were asked to select their preferred flavor. For each flavor, there was both a regular version (e.g., vanilla) and a reduced-fat version (e.g., reduced fat vanilla). The difference between the groups was this: in the “low-variety condition,” there were just two options available: one regular and one reduced fat. In the “high-variety condition,” there were 10 options available: five in each category.

Yummy! Ten varieties of ice cream! That group chose the most sinful options available, right? Well, of course not.

Surprisingly (at least for ice cream lovers), the participants who chose from the larger assortment were more likely to select a reduced-fat flavor—the virtuous option. A subsequent experiment offering cookies or fruit got the same result.

Why? These researchers concluded that “because choosing from larger assortments is often more difficult, it leads people to select options that are easier to justify. Virtues … are generally easier to justify than indulgences.”

Advice for marketers? The researchers suggest that manufacturers of healthy snacks or other more virtuous products may be better off “pursuing venues with larger selections.”

Match size to substance. Before you decide on an assortment size, figure out if your product is a vice or a virtue.

Source: “Variety, Vice, and Virtue: How Assortment Size Influences Option Choice,” by Aner Sela, Jonah Berger and Wendy Liu, Journal of Consumer Research

Skip Sommer