Use “pseudo-sets” to control how many actions people take

When you group tasks or items into a set that when reached feels ‘complete’, you encourage people to reach that exact number.

This fascinating research was published 3 years ago by IESE and Harvard researchers and builds on Gestalt psychology (“the whole is greater than its parts”) - first studied over 100 years ago.

It shows us how we can influence people to take more, or less, actions (e.g. reading or buying something, going to the gym) by grouping them into sets that feel ‘complete’.

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Group tasks or items into pseudo-sets to encourage people to reach that goal

Impacted metrics: Engagement | Customer spending | Purchase frequency
Channels: Website/app | Product

“Suppose you were asked to participate in a charitable service project by writing greeting cards to isolated senior citizens. You could complete as many or as few cards as you liked. How many would you write? And how would you determine when to stop? Perhaps you would write a card, maybe two, and finish when your output felt “good enough.”

Now imagine learning that the greeting cards would be arbitrarily batched in sets of four, or discovering that your card-writing progress would be tracked as part of a four-slice pie chart that “filled in” as you went. How might this change your stopping point?”

- The introduction of the paper explains the concept very well


Create and communicate clear ‘pseudo-sets’ to persuade people to complete a certain number of tasks (you’ve read 1 out of 4), encourage a specific number of donations (donate 6 packs, 1 for each family member), or buy a group of products (collect all 5 candles). 

People will stop at the reference point you set, but they are much more likely to reach it rather than abandoning earlier.

For example, a gym could encourage members to workout 2 times per week, enough to keep paying the subscription, but not too much that it becomes overcrowded.


  • Pseudo-sets are groups of tasks or items that when reached give a sense of ‘completeness’ (e.g. filling a pie chart, 100% completion).

  • They encourage people to complete exact sets (or multiple of them) of tasks or items, without changing the tasks or incentives.

  • The effect works whether the pseudo-sets have meaning (e.g. write 4 letters, because we ship them in batches of 4), or none at all (e.g. a 4 part pie chart counting the number of pages read on the BBC news website, would make it much more likely that people read multiples of 4, or stop at the first 4).

  • It works to encourage moderate effort, but if the goal is too high the effect backfires. People will be dissatisfied - and abandon - before they even start.

Why it works

  • Framing tasks or items in pseudo-sets works by (a) conveying the notion of a larger group or entity, which (b) increases perceptions of incompleteness, and in turn (c) activates people’s desire for completeness.

  • We naturally find complete, cohesive units to be symbolic and meaningful, so we strive to achieve them. Think of the slight annoyance you may feel when buying a ‘6 pack’ of sodas with 1 missing.

  • If the goal is too high to achieve (e.g. workout 10 times this week), we expect we won’t reach a satisfying endpoint - so we won’t even start it.


  • The researchers ran several experiments, and similar human behaviors have been well researched in the past decades. This study is widely applicable.

  • The main limitation to keep in mind is that this is a nudge to tweak a behavior, not drastically change it. Don’t expect to sell 3x the amount of laptops by selling them in sets of 3 ‘collectible’ colors (the effort required vs value received for something like that is on vastly different levels).

Companies using this

  • Pseudo-set framing is widely used in areas like web design (“you’ve read 66% of this article”. Really), gaming (“unlock 8 new levels”), and collectible products (e.g. cards, toys).

  • However, it could be used much more widely in areas like social good (e.g. a pie chart showing you’ve used bike-sharing 2 out of 5 times this week, to encourage healthy behavior without straining capacity), services (“you’ve tried 1 of 4 spa treatments”), employee welfare and productivity (“take four 10 minute breaks during the day”), or digital wellbeing (“you’re at 80% of your time on your phone today”, as some apps do already).

  • These effects could also be applied to new product categories not normally seen as ‘collectibles’, since the researchers found that pseudo-sets don’t need to have meaning.

Steps to implement

  • Select an action of your customers, users, employees, or citizens that you would like to increase or reduce.

  • Test the number of tasks/items that work best. It can require moderate effort, but not more, or it will backfire. The ideal number may require too much effort (e.g. asking someone who never ate fruit to suddenly eat 5 per day. Try starting with 2).

  • For example, if you see that most users abandon your website after 3 pages, try adding a counter (e.g. a pie chart with 6 parts that tracks progress at each visit). It will guide users to read 6 pages. But be careful, it will also encourage those who would have read more than 6 to stop, and might be a barrier for people to return to your website if they don’t want to put the effort into reading 6 pages again.

Study type

Field, lab, and online experiments, United States


Barasz, K., John, L. K., Keenan, E. A., & Norton, M. I. (October 2017). Pseudo-set framing. Journal of Experimental Psychology, 146(10), 1460.

[Link to paper]


IESE Business School and Harvard Business School

Remember: This research could be disproven in the future (although this is rare). It also may not be generalizable to your situation. If it’s a risky change, always test it on a small scale before rolling it out widely.

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