January 3, 2021 2 Comments

Set-Fit Effect

bundling inferior items together can make the items look more valuable than they actually are

cool paper in 3 min (13)

Suppose I give you two pens to choose from. One is clearly better than the other. You will, most probably choose the better one. Now what if I tell you that, no matter which pen you choose, you also get 3 extra pens similar to the bad one. Would these free add-ons make you change your mind and choose the less good pen?

Does this sounds like a crazy question to ask? In a magically short and clearly written paper, Ellen Evers and colleagues show that people do in fact fall for this simple trick and change their mind. The paper provides 4 creative experiments that ask “can forming a good set be a source of economic value in and of itself“?

Below, I have illustrated 3 of their experiments.

Experiment 1. Top: Pie chart shows that most people preferred the (good) metal pen over the (bad) plastic one. Bottom: when the same bad pen is offered together with a group of similar bad plastic pens, suddenly a lot more people (50%) choose this “good set” group over the other set that includes one good pen and 3 bad pens. In other words, the yellow part of the bottom pie chart has expanded purely because the bad pen “fits” with the others but the good pen does not.

Experiment 2. Which set of paper-clips do you prefer? Top: One set (left) consisted of 4 colourful (red, green, yellow and blue) clips. The other set (right) consisted of three exact same colourful clips (red, green and blue) and one, oddball metallic one. Most people (yellow segment of pie chart) preferred the colourful set on the left. Bottom: The same yellow and metal clip were now added to three metal clips (rabbit, duck and penguin). This time, most people (green segment) preferred the metal set on the right. In each case, the set with the oddball was less likely to be selected.

Experiment 3. Children (around 7 yr old) too prefer homogenous sets with similar items. Top: when presented individually, most children prefer the fancy blue marble with white stripes (right) over the simple plain marble on the left. Bottom: when choosing between two sets of marbles, however, children prefer the homogenous set of 4 plain marbles to the irregular set of 3 plain and 1 fancy marble.

These experiments show that fitting in a set can modify our preferences over the set’s individual items. This is important because it can be used to create marketing offers by ‘bundling’ a number of inferior similar items (e.g., 2 for 1 offers) together and exploit the “good set” effect that it creates in costumers without having offered any extra value.


  • Bahador Bahrami

    @mitra_eft this is very interesting indeed. Maybe we can work with your company and do some research on this topic


  • Mitra

    This exact bundling is used in dealing with pharmacies and ends to the replacement of your prescribed brand to the ones they stock as a bundle


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