Mind & Body

Can Shapes Be Angry? Scientists Put Our Emotional Perception to the Test

Ever wondered why valentines are rounded but caution signs have hard edges? What about the difference between the soft, fluffy shapes we use in children's nurseries and the angled, spiky designs on heavy metal albums? Don't worry if your answer is no: Most of us never give those things a single thought. The matches just feel so natural. Now, new science suggests that's because the human brain automatically applies emotion to inanimate objects. So, yes, some shapes can be angry — and that has implications for how we perceive everything around us.

It's All About That Spectral Centroid

Generally speaking, humans are really good at detecting emotion. We can tell if someone's angry, embarrassed, or surprised based on small shifts in their body language or tone of voice. And for over a century, we've known that humans associate certain sounds with certain shapes.

A recent study by Beau Sievers at Harvard University explored that ability to sense emotion and how it could apply to shapes and sounds. It turns out that our emotional associations are so strong that we also unconsciously apply them to inanimate objects.

While previous research has already shown something like this to be true, this team wanted to explain why. Their hunch was that humans of all cultures both encode and decode these automatic connections between shapes, sounds, and emotions with a property called the spectral centroid. The spectral centroid is an equation that relies on the idea that you can break an image or sound into a spectrum of different frequencies. For example, a curvy shape has lower frequencies than a spiky one. Scientists take the average of each shape's frequency spectrum to get its spectral centroid.

What Sievers and his colleagues wanted to learn was whether the spectral centroid could be used to determine levels of emotional arousal. The hypothesis: anger and excitement involve high arousal and could be associated with spiky shapes and a high spectral centroid. The inverse would be true for sad, peaceful emotions.

Which is sad, and which is angry?

What's the Shape of Your Sadness?

To start, Sievers and other researchers on his team asked participants to match shapes and sounds to feelings. Sure enough, they matched sharp shapes and bursts of white noise to anger and excitement — and no surprise, those sounds and shapes also had high spectral centroids. And "round" sounds and shapes had lower spectral centroids and were matched to peaceful or sad sounds.

Next, the researchers asked another group of participants to draw their emotions. You can do this for yourself at home. How would you draw your excitement? What about your sadness? Anger? Joy? Most likely, you'd draw just what these participants did: sharp shapes for anger, rounded ones for sadness. When scientists calculated the spectral centroids of each participant's shape, they could predict the emotional label with almost 80 percent accuracy.

A Universal Code

The fact that there's a universal emotional quality to sounds and shapes lends support to a hypothesis that goes all the way back to Darwin, who believed that humans could understand the emotions of other animals from the sounds they make. In 2017, a study demonstrated that people could guess the true emotional state of eight different animals — from pigs to treefrogs — just from hearing their calls. This study suggests that those participants were probably using the spectral centroid to make their judgments, even if they didn't realize it.

While more research is warranted, Sievers and his team have high hopes for their findings. They conclude their study with the hope that "we can build a deeper understanding of how communication can transcend immense geographic, cultural, and genetic variation." So the next time you feel like you can't understand how someone is feeling, ask them to draw it for you. Science says you'll understand immediately.

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Learn more about the universality of emotion in "Mama's Last Hug: Animal Emotions and What They Tell Us About Ourselves" by primatologist Frans de Waal. The audiobook is free with an Audible trial. We handpick reading recommendations we think you may like. If you choose to make a purchase, Curiosity will get a share of the sale.

Written by Kelsey Donk September 24, 2019

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