You’ve probably seen ads for apps promising to make you smarter in just a few minutes a day. Hundreds of so-called “brain training” programs can be bought for download.

These simple games are designed to challenge mental abilities, with the ultimate goal of improving the performance of important everyday tasks.

But can just clicking away at animations of swimming fish or flashed streets signs on your phone really help you improve the way your brain functions?

Two large groups of scientists and mental health practitioners published consensus statements, months apart in 2014, on the effectiveness of these kinds of brain games.

Both included people with years of research experience and expertise in cognition (认知), learning, skill acquisition, neuroscience and dementia (痴呆). Both groups carefully considered the same body of evidence available at the time.

However, they issued exactly opposite statements.

One concluded that “there is little evidence that playing brain games improves potential broad cognitive abilities, or that it enables one to better handle a complex condition of everyday life.”

The other argued that “a large and growing body of evidence shows that certain cognitive training methods can significantly improve cognitive function, including in ways that generalize to everyday life.”

Brain training programs are an attractive shortcut, a “get smart quick” scheme. But improving or maintaining cognition is likely not going to be quick and easy. Instead, it may require a lifetime — or at least an extended period – of cognitive challenge and learning.

If you’re worried about your cognition, what should you do?

First, if you do engage in brain games, and you enjoy them, please continue to play. But keep your expectations realistic. If you’re playing only to obtain cognitive benefits, instead consider other activities that might be as cognitively inspiring, or at least more rewarding — like learning a new language, for instance, or learning to play a musical instrument.

Does stress cause gray hair? Many people believe that tension and stress can cause your hair to lose its color. In fact, it is an old-wives’ tale that being upset all the time can result in premature graying. Here is a closer look at this situation and why some believe that this old wives’ tale could be true.

As one ages, the hairs on the head also age. In fact, just about everything on the human body begins to show signs of wear and tear (磨损) after a while. The joints wear and become stiff and skin wears and becomes wrinkled. Hairs on the head grow and eventually die. They are replaced, but in the process something else happens.

When new hairs are replacing the old ones, the color or pigment (色素) is also added to them. However, as one ages, this pigment becomes less and less available. At first, hairs will have a limited amount of pigment and they will appear to be grayish in color. In time, they will lose all of their pigment and will be white. Many things are known to cause graying, and genetics is a very powerful factor. If one of your parents turns gray at an early age, there is a good chance that you will too. Some people begin the graying process in high school, while others may be over the age of forty.

Constant worry and tension can have many harmful effects on the human body. It is a known fact that stressful times can cause one to suffer hair loss. It would make sense that if it can cause these problems, perhaps it also may contribute to graying. However, there is no sound evidence to support this.

On the other hand, many medical professionals believe that there may be a link between graying and a constant state of anxiety or tension. Does stress cause gray hair? There is no scientific evidence to support the theory, but it is best to avoid stressful situations.