This is the first edition of my new blog series on neurodesign. In this series, I’ll discuss principles of neurodesign and the psychology of design you can use in your business in order to maximize positive results from your designs. The first principle I will discuss is the Contour Bias.
Contour Bias: People have a natural tendency to prefer objects with contours (curves) over those with sharp angles or points. Psychology and design researchers believe this preference comes from humans’ tendency to significantly prefer objects that look natural over objects that look synthetic.
In nature, both objects and settings are rife with curves. For example, simply look at the setting below:

And compare that to the NYC skyline, which is rife with sharp angles, points, and rectangles.

Further, sharp angles are usually dangerous! Think about a lion’s tooth, a bear’s claws, or a sharp household object that might hurt you or your loved one.

Evidence for the contour bias has been shown in experiments. Researchers have tested this with both surveys (subjective measures) and biometric testing (objective measures).

In opinion surveys, the participants significantly preferred the rounded objects over the angled objects; for example, a round-faced watch over a square-faced watch (1).
In fMRI studies, the degree of amygdala activation was measured when subjects viewed both contoured and sharp-angled objects. For context, the amygdala is the “fear center” of the brain (2). It has also been shown to play significant roles in the formation of long term memories and helping one determine whether a stimulus is positive or negative (more on the amygdala in layman’s terms here).
When researchers measured amygdala activation for contoured objects vs. angled objects, they found significantly more activation for those with angles. Further, they found that the degree of amygdala activation was inversely proportional to object preference. That is, the more sharply-angled the object, the less it was liked (1).
It is a bit more complicated than just saying:
“Just make your designs curved if you want them to be liked.”
Researchers minimized “expectation bias” in the aforementioned experiments by using “neutral” objects. That is, objects that could be either round or square without their function being significantly changed. This would include objects like watches, smartphones, pocket calculators, or dinner plates. It would not include objects like knives or baby dolls. Further, there are some cases in which using sharp angles in your designs may be useful! Although angled objects tend to be less liked, they have two redeeming factors. First, they elicit a higher level of memory activation, meaning they are more memorable. Second, they are more effective at capturing attention.
In short, you may think of contours like this: contoured objects are more liked, so they can help you maximize positive impressions both emotionally and aesthetically. Sharp objects are both more easily recognized and memorized, meaning they can help you more easily get your audience’s attention.
How can you apply this to your designs?
Based on the research, it is my opinion that you should use both contours and angles in your design. As I mentioned in the last paragraph using both can help you more effectively influence your audience’s attention and interest. You won’t get interest without first getting attention, so it is (by and large) prudent to work to influence both.
Next, I will show you some examples of this principle in practice. First, one of my own designs!

As you can see, I used curves on the “Learn More” button to make it more closely match a button that would appear in nature. However, I did not make it a completely rounded circle. Instead, it’s in the shape of a leaf to help match the aesthetic of the website, which is focused on the beautiful nature of Hocking Hills. I also used rounded corners on the podcast player and on the weather widget in the top-right corner.

Other companies have started catching onto the contour bias as well. For example, #imgrc=8QFpl767ztLp_M” target=”_blank” rel=”noreferrer noopener”>remember how Google used to look? Rectangles. Rectangles everywhere!
Compare that to how it looks now (screenshot captured April 2023):

As you can see, Google designers significantly increased the roundness of the Google search bar. I don’t know about you, but I like that rounded look a lot more.
Old Apple devices were also once remarkably square. For example, just look at the old PowerBooks. Now, basically all of their devices have that “squircle” look. That is, a square with slightly rounded corners. See a great example with the latest Apple devices below:

They found their “squircle” look so important that they even managed to patent it. Their multi-hundred million dollar lawsuit against Samsung in the early 2010s even included charges that Samsung stole this look. Evidently, Apple considers rounded corners an integral part of its business success, so another company “borrowing it” was not something they took lightly.
Summary:
People have a natural tendency to prefer objects with contours (curves). Sharp-angled objects tend to elicit amygdala activation and are also less liked. However, this does not mean you should always use curves in your design and never use sharp angles. Instead, it is often practical and effective to use both. Use curved objects to maximize positive emotions and impressions in your designs. Use sharp angles when you would like to increase the attention and make a certain element in your design more memorable. For example, if you have a table at a conference, you might use sharp angles to capture attention and curved angles to leave a positive impression for your visitor
If you have any other questions about how to apply this to your designs, leave a comment below or send me a message! 👋
References:
- Humans Prefer Curved Visual Objects by Moshe Bar and Maital Neta, Psychological Science , 2006.
- Discovering Behavioral Neuroscience by Dr. Laura. A Freberg