When you are out in a store, looking for something specific, you usually compare a number of products regarding their features and functionality. Only after you did this, you make your choice and decide which one to buy. When comparing, you are confronted with a wide range of product differentiation, which makes comparison even more fruitful but also harder.

Psychologists have been doing a lot of research about this phenomenon and created a model of choice – the so-called cancellation-and-focus (C&F) model. With this model the arbitration between choices with unique or shared attributes can be predicted and explained. Former research endorses greater emphasis of unique attributes in the decision-making process and the “cancellation” (ignorance) of shared attributes. However, that this phenomenon applies has only been proven for text descriptions of choice alternatives.

In a design context this outcome would only be useful if the same phenomenon would occur with actual product visuals. Therefore, Ping Du, Graduate Student in Mechanical Engineering at the Iowa State University and Erin F. MacDonald, Assistant Professor in Mechanical Engineering at Stanford University conducted an eye-tracking study combined with the traditional survey method regarding this issue.

With eye tracking researchers are able to investigate how respondents visually evaluate products, for how long they fixate certain areas (fixation time) and how often they look at that certain area (fixation count). Based on that data it is possible to draw areas of interest (AOI), which are user-defined selections of one or many areas, revealing their attention results.

Du and MacDonald’s study has been executed under different conditions, divided into the representation mode, where “text-only”, “image-only” or “image-with-text” have been shown, and the presentation of choice alternatives (sequentially, or side-by-side). The outcome of the study showed that in a design context the cancellation-and-focus model only applies in a few situations. Even the cognitive responses from eye-tracking and survey data to shared image features vs. shared text attributes differ significantly. The replication of attributes in an image supports the importance of such in a decision-making process, while its replication in “text-only” ignores it.

Du and MacDonald’s study confirms that the unique features attract more gaze attention than the shared features. However, the study also finds that the shared features are not cancelled and they can affect consumer decisions. It was observed that when only the product images were provided, the unique-good product pair (a pair that shared the same bad feature designs but have unique good feature designs) left worse impressions to the participants than the unique-bad pair (a pair that shared the same good feature designs and have unique bad feature designs) in some cases. This indicates the importance of the shared features. This fact is especially important for designers that want to design into a crowded market. They need to be careful about features that will be shared with other products. Ideally, product designers would therefore focus on both differences and commonalities since the former ensures attractiveness while the latter can affect impressions.

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