A nudge is a suggestion, a small incentive, but it can have big consequences on the outcome.
Placing certain products at or just above eye level in the shop is a nudge to consider these (presumably, most profitable) items first. Placing broccoli early in the lunch line-up leads people to get it more often, improving nutrition. Automatic enrollment in 401k is a strong nudge to save for retirement, since the money will go in automatically. Enrollment in a gym isn't much of a nudge, but signing up for a group exercise class or sessions with a trainer may work as a nudge and encourage attendance.
The nudge can come from a policy, from a physical environment, or from software. Mozilla Thunderbird is smart enough to nudge the user to actually attach a file if it finds the word "attachment" in the text. Amazon.com and many other online retailers learned to nudge customers to write reviews, and to rate reviews left by others. Word processors nudge users to correct the spelling and sentence syntax by visually marking unknown letter sequences.
However, there is plenty of software that is less helpful than it could be if it was to nudge the user to follow better practices.
- PowerPoint offers no nudges to produce good presentations - small font is as easy to reach as large, bullets go in indefinite layers with no suggestions to keep it simple.
- Modern IDEs have a lot of great capabilities to help write readable code, but don't yet automatically generate nudges to rename and refactor.
- Software like Infinitest nudges the developer to update unit tests regularly to keep them passing, but not to write new ones.
- Neither Wordpress nor Blogger.com nudge to limit the size of the blog post, suggest pagination, and do not remind to include pictures (but not too many pictures).
Behavioral research shows that nudges work. Yet, in order to work and improve performance, nudges need to be carefully designed and created. Software design industry is currently in the early stages of learning how.