Mental Models
Mental Models are a powerful way to describe what is going on inside user’s brains. It gives us more cues about how they perceive certain things so we can empathize with their experiences [1]. Viable cues concerning mental models can be identified via different methods. A popular one is card sorting, it is especially relevant for challenges concerning information architecture. Furthermore, we can get a better understanding of user’s processes by observing how they interact and act in their current environment. Specifically in the grocery and retail context so called “PLU-lists” are a major artifact.
PLU-List
Every customer of a supermarket has already been exposed to this code – wether they know it or not. A PLU number is an international code, that defines products like fruits and vegetables. The PLU code for a banana typically begins with the number 4. Additional information, like country of origin of the product can also be identified through this code. Sometimes employees know this number, or at least specific selected numbers, by heart. In case they have to look it up, they have to take a look at a list – this is also where the name stems from: PLU stands for price-look-up code. [2]
Possibilities for informal user research with high value and impact
I’m aware this might be a bold move, but I believe that a lot of online forums, especially via reddit, can be an interesting way to observe user’s and customer’s behaviour. This works for both – in a market research as well as a design related user research way. While this is obviously an informal way of researching something, I strongly believe it is of high value. It gives you first hand impressions of customers, and possibly even employees.
Subreddit “Target”
Down below I have found a picture, this is an example from Target that I found via Reddit. It was attached to a post, where an employee reached out to the forum in the r/Target subreddit, because they were curious about which codes are popular and commonly used.
Source: Reddit | r/Target | User: csrlrnz
Subreddit “schei**aufnbilla”
While this subreddit has a rather extrem title, it definitely opens a new horizon concerning honest opinions of angry customer’s.
Reviews
In contrast to reddit google reviews covers a larger range of customers. Clicking through various stores on google maps quickly gives you a good overview of different challenges customers and sometimes even employees face. This works efficiently via google maps, because they also give you options to filter the different reviews (e.g. by keywords)
Sources
[1]
M. Chan, “Mental Models and User Experience Design,” Nielsen Norman Group, Jan. 26, 2024. https://www.nngroup.com/articles/mental-models/
[2]
Bayerischer Rundfunk, “Lebensmittel Code entschlüsseln: Was bedeutet der PLU-Code auf Lebensmitteln?,” Www.br.de, Mar. 11, 2024. https://www.br.de/radio/bayern1/lebensmittel-code-entschluesseln-100.html (accessed Jan. 30, 2026).
