In the early study of emotional expressions, researchers believed humans only had six basic emotions: anger, disgust, fear, happiness, sadness and surprise. Later researchers believed there might be as many as seven or eight. Every emotion was shoehorned into one of those categories.

That didn't make much sense to Aleix Martinez, a cognitive scientist and professor of electrical and computer engineering at The Ohio State University.

"I always figured that was very strange for many reasons," Martinez tells MNN. "First, it was a small number. But more important, why so many negative emotions and only one happy expression? We tend to be more happy than angry or disgusted."

After a recent study that involved more than 7 million online images and 30 countries, Martinez found there are actually 35 different expressions that are recognized across cultures. Of these, 17 of them convey happiness.

"It was reassuring to me that we are a happier society and world than we thought," Martinez says. "Almost half of the expressions we identified were positive ones."

Studying millions of faces

To figure out how many expressions translate across cultures, Martinez first had to start with a list of possible feelings. He and his team identified 821 words that are associated with emotions, such as anger, frustration, love and happiness. They had these words translated into Spanish, Mandarin Chinese, Farsi and Russian by professional translators. Then the words were used to mine the web in popular search engines in 30 countries.

The process resulted in about 7.2 million images of faces that reflected those specific emotions. Each image was coded by a computer algorithm using a measurement called action units (AUs) which represent the muscular activity that trigger changes in facial appearance. They were sorted into categories of emotions that spanned all the cultures studied.

Because the human face is capable of configuring itself in 16,384 unique ways, Martinez figured they would come up with at least 100 or more expressions that were the same across all cultures. He was surprised when they found only 35.

"We were shocked," he says. "I thought there would be way, way more."

The study was published in the journal IEEE Transactions on Affective Computing.

Why so much happiness?

Humans have the ability to convey so many different emotions, but it's fascinating, Martinez says, that we have a rainbow of ways to express happiness while only one way, for example, to show disgust.

"The most likely explanation is if I find something really disgusting or you do something and that I find morally disgusting, one expression is sufficient to convey my disgust," he says.

Happiness however, comes in so many shapes and sizes, from slight pleasure to extreme euphoria. And a person's face may show the difference simply by a wider smile, brighter eyes or more crinkles around the lips or eyes.

The study also found that we use three expressions to show fear, four to convey surprise, and five each to express sadness and anger.

Martinez doesn't yet have names for the 17 different expressions of happiness, but he's working on. The good news, he says, is that we definitely have more than those eight basic emotions.

"To think that humans are only capable of eight emotions is absurd," he says, in a statement about his research. "We are complex creatures. What about the different forms of joy? We experience the world on a much deeper level than just eight emotions."

Mary Jo DiLonardo writes about everything from health to parenting — and anything that helps explain why her dog does what he does.

You have 17 different facial expressions to show happiness (and that's reason to smile)
From slight pleasure to extreme euphoria, our faces convey happiness more than any other emotion.