Complementary products boost your main product

A rich display of complementary products attracts attention to your main product and boost its sales. The more varied the display the better.

This Swedish-American study used eye-tracking in a retail environment to observe how different product arrangements attract our attention and boost sales.

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Previous tip: How to reduce choice overload and increase satisfaction (All tips here)

Use complementary products to increase attention for your main product

Impacted metrics: Customer acquisition
Channels: Product placement | Promotions | Retail store | Ecommerce sales


Surround your main product with complementary products (e.g. sauces, accessories, add-ons) to attract more attention to it and increase sales.

The more complex and varied the assortment of complementary products (from flavors to colors, to different shapes), the better.


  • When a main product (e.g. hummus) is surrounded by complementary products (e.g. pita bread, carrots, dipping chips), we will pay more attention to the assortment and are more likely to buy the main product.

  • This effect also works if we don’t see the main product yet (e.g. it’s in a freezer, or you need to scroll down the page). Complementary products commonly associated with a product (e.g. hotdog condiments), can trigger our search for the main product (e.g. hotdogs).

  • The larger and more varied the display of complementary products, the stronger the effect. Particularly if they are different colors and shapes (e.g. orange carrots, red bell peppers, a loaf of sourdough bread, flat pita bread).

(Likelihood of choosing the main product in one of the experiments, depending on how many and how varied the complementary products surrounding it are - Click to zoom in)

Why it works

  • Displays of a large variety of products attract our attention. The downside is that we can easily go into choice overload, and become less likely to buy (read about this effect and how to mitigate it here). However, in this case, we use complementary products to concentrate this increased attention on a single ‘focal’ product, increasing its sales.

  • The quality of this large variety makes a difference because we find displays with high design complexity (different shapes, objects, arrangements) more likable, interesting, and engaging. Think of award-winning shop window displays during Milan’s fashion week or at Harrods in London during Christmas.


  • The study focused on in-store marketing of groceries (chips and frozen food). The effects should hold for other product types (e.g. electronics) and situations (e.g. fast food restaurants), but that was not directly tested.

  • It seems the effect only works if the main product is one. If there are variations of the main product (e.g. different flavors) the effect is diluted because people start to experience choice overload.

  • It’s not clear if the effect works the other way around: does seeing the main product also transfer attention to the complementary products?

Companies using this

  • Complementary products are often used to promote a main product in grocery stores. Fashion stores and fast food restaurants also sometimes use this technique.

  • It’s more common offline, but occasionally happens online. Think of Amazon’s “customers also bought this”.

Steps to implement

  • Use this technique to heavily promote a specific product. For example, if it’s new to the market or has high margins or branding value.

  • Think out-of-the-box to apply this online. For instance, if you’re a women’s fashion ecommerce store and you’re launching a special edition dress, you may want to promote it on a specially designed page, surrounding it with related complementary items (e.g. bags, shoes).

Study type

Lab and field experiments, United States and Sweden


Radon, A., Brannon, D. C., & Reardon, J. (October 2020). Ketchup with your fries? Utilizing complementary product displays to transfer attention to a focal product. Journal of Retailing and Consumer Services, 58, 102339.

[Link to paper]


Södertörn University and Monfort College of Business, University of Northern Colorado, Sweden and United States

Remember: Because of the groundbreaking nature of this paper, it 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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