I’m a special needs teacher. We don’t usually get storms in May. We were having a fairly unremarkable school day and I’d seen the last of my class of five-year-olds leave when my dad rang to warn me that there was a storm heading straight towards us. At first, I thought he couldn’t be right, but then the storm alarm went off. My own daughter, Kali, was at the school, in the kindergarten class across the hall, and that’s where I headed. Her teacher, Jennifer, was following the standard procedure: moving the 10 children into the hallway,getting them to kneel (跪下) with their elbows on the ground, hands over their heads.

We encouraged the children to sing, to keep up their spirits,but when the sky grew dark dim and the lights went out, it became harder to keep everyone calm. Hail (冰雹) and broken glass showered into the hallway. Instinctively, Jennifer and I took five children each and lay across them. It wasn’t something we had to think about. They were small children; we were adults and we would protect them with our lives. My daughter was among them. I just kept saying over and over, “We’re going to be OK. We’re going to be OK.” But soon I couldn’t hear my own voice above the sound of the school’s metal roof exploding under huge pressure.

Then came a big noise so loud that I’ll never forget it, like a plane but 10 times louder. It was the storm passing directly overhead. Suddenly I realised the roof had gone; the wind had torn it clean off.   We were at the mercy of the elements. My mouth was filled with dirt and I wondered if we were going to be buried alive. Beneath me, the children were packed together tightly. I did my best to cover them, but there was water, too, pouring down. Then I felt a blunt thing against my back. By now, I was simply repeating to myself, “Please go away. Please go away.” I just wanted it to stop.

By the time it did,

Fortunately, no children died or hurt in the storm.

Mental health conditions, including everything from depression and phobias (恐惧) to anorexia (厌食) and schizophrenia (精神分裂症) are shockingly common. In the UK, one in four people experience them each year, so it is likely that you, or someone you know, has sought help from a professional. That process usually begins with a diagnosis. Then you start on a treatment tailored to your condition. It seems an obvious approach, but is it the right one? “For millennia, we’ve put all these psychiatric (神经病的) conditions in separate corners,” says neuroscientist Anke Hammerschlag at Vrije University Amsterdam, the Netherlands. “But maybe that’s not how it works biologically.”

There is growing evidence that she is correct. Instead of being separate conditions, many mental health problems appear to share an underlying cause, something researchers now call the “P factor”. This realization could thoroughly change how we diagnose and treat mental health conditions, putting more focus on symptoms instead of labels and offering more general treatments. It also explains puzzling patterns in the occurrence of these conditions in individuals and families. Rethinking mental health this way could be revolutionary.

At first glance, the idea that different mental health conditions with distinct symptoms share an underlying cause seems unrealistic. The key to understanding it lies in its name. “P factor” has intentional parallels with one of the most famous concepts in psychology. More than a century ago, British psychologist Charles Spearman noted that children’s performance on one kind of mental task, say verbal fluency, was correlated with their mental skill in other areas, like mathematical reasoning, spatial manipulation and logic. In other words, children who are good at one thing tend to be good at another, while those who struggle in one area tend to struggle in others. Using a statistical tool called factor analysis, Spearman showed that this is because these different mental abilities are all linked to an overarching cognitive capacity, which he named general intelligence, or the “G factor”.

10 . On March 7, 1907, the English statistician Francis Galton published a paper which illustrated what has come to be known as the “wisdom of crowds” effect. The experiment of estimation he conducted showed that in some cases, the average of a large number of independent estimates could be quite accurate.

This effect capitalizes on the fact that when people make errors, those errors aren’t always the same. Some people will tend to overestimate, and some to underestimate. When enough of these errors are averaged together, they cancel each other out, resulting in a more accurate estimate. If people are similar and tend to make the same errors, then their errors won’t cancel each other out. In more technical terms, the wisdom of crowds requires that people’s estimates be independent. If for whatever reasons, people’s errors become correlated or dependent, the accuracy of the estimate will go down.

But a new study led by Joaquin Navajas offered an interesting twist (转折) on this classic phenomenon. The key finding of the study was that when crowds were further divided into smaller groups that were allowed to have a discussion, the averages from these groups were more accurate than those from an equal number of independent individuals. For instance, the average obtained from the estimates of four discussion groups of five was significantly more accurate than the average obtained from 20 independent individuals.

In a follow-up study with 100 university students, the researchers tried to get a better sense of what the group members actually did in their discussion. Did they tend to go with those most confident about their estimates? Did they follow those least willing to change their minds? This happened some of the time, but it wasn’t the dominant response. Most frequently, the groups reported that they “shared arguments and reasoned together”. Somehow, these arguments and reasoning resulted in a global reduction in error. Although the studies led by Navajas have limitations and many questions remain, the potential implications for group discussion and decision-making are enormous.