Many of the psychological benefits of outdoor play are already well established. Our brains evolved in natural landscapes, and our perceptual(感知的)systems are particularly well suited to wild outdoor spaces. 

This means that natural scenes provide the perfect level of stimulation, which is thought to help recharge the brain when it is tired and easily distractible. Supporting this theory, one study found that children with attention-deficit hyperactivity disorder (ADHD) were better able to concentrate following a 20-minute walk in the park, compared to a 20-minute walk on the streets of a well-kept urban area. Being exposed to grass and trees seemed to have had a beneficial effect on their minds. The authors recommended using such "doses(剂量)of nature" as a safe and accessible way of supporting children with ADHD, alongside other tools.

Besides these restorative effects, outdoor play can offer valuable learning experiences. For example, playing with mud or sand can help children develop the way their senses and movement interact, which allows the child to gradually understand his or her body signals. 

Such activities — away from the house or classroom — may also help children to find ways to cope with emotions that maybe hard to explore in other environments. So-called "sand tray therapy", which involves using sand and clay to express one's thoughts and feelings, is an accepted form of counselling for children who are struggling to verbalise their emotional state.

When it comes to the child's physical health, the most obvious advantage of outdoor play maybe the exercise A child may find it easier to buildup strength and endurance in a large open space resulting in a reduced risk of overweight, according to one study led by Elizabeth Gershoff, professor of human development and family sciences at the University of Texas at Austin, US.

The latest findings, however, suggest there could be a host of other advantages to playing in natural environments — and the secret maybe alive in the mud itself. 

New research has found that young adults who smoke both tobacco cigarettes and e-cigarettes appear to have a higher risk of stroke than those who only smoke tobacco.

Carried out by researchers at George Mason University, the new study looked at 161 ,529 participants aged 18 to 44 years of age， who were surveyed about their cigarette and e-cigarette use.

The researchers also calculated the participants' risk of experiencing a stroke, taking into account factors such as how much participants smoked, high blood pressure, diabetes, cholesterol levels, body mass index and physical activity levels.

The findings, published in the American Journal of Preventive Medicine, showed that the participants who smoked cigarettes and used e-cigarettes were nearly two times more likely to have a stroke compared to current cigarette-only smokers, and nearly three times more likely than non- smokers.

The team also found that participants who used only e-cigarettes had a lower risk of stroke than those who smoked only tobacco cigarettes. In fact, those who used e cigarettes on their own did not have a significantly greater risk of stroke than nonsmokers.

However, the researchers failed to find any clear benefit from switching from cigarette smoking to using e- cigarettes，even though many people believe that e- cigarettes are a "healthy" alternative to cigarettes, and a way to help smokers kick the habit. They also noted that the nicotine dependence and toxicity associated with e-cigarettes is worrying, particularly among young adults who smoke them for fun and the range of flavors.

"It's long been known that smoking cigarettes is among the most significant risk factors for stroke. Our study shows that young smokers who also use e-cigarettes put themselves at an even greater risk," explained lead investigator Tarang Parekh, MBBS, MSc."This is an important message for young smokers who perceive e- cigarettes as less harmful ones and consider them a safer alternative. We have begun understanding the health impact of e-cigarettes and concomitant cigarette smoking，and it' s not good."

"Our findings demonstrate an additive harmful effect of e-cigarettes on smokers' blood vessels, hearts and brains,"explained Parekh.

"Consider this study as a wake-up call for young vapers, clinicians, and healthcare policymakers. There is an urgency to regulate such products to avoid economic and population health consequences and a critical need to conduct further research on the benefits and risks of smoking cessation alternatives," warned Parekh.

    They had a dozen children, six boys and six girls, in seventeen years. One reason Dad had so many children was that he was confident anything he and Mother teamed upon was sure to be a success.

    Our house at Montclair, New Jersey, was a sort of school for scientific management and the removal of wasted motions — or “motion study,” as Dad and Mother named it.

    Dad took moving pictures of us children washing dishes, so that he could determine how we could reduce our motions and thus hurry through the task. Each child who wanted extra pocket money put forward an offer saying what he would do the job for. The lowest bidder got the contract(合约).

    Dad put process and work charts in the bathrooms. Every child old enough to write — and Dad expected his children to start writing at a young age — was required to sign their names on the charts in the morning after he had brushed his teeth, taken a bath, combed his hair, and made his bed. At night, each child had to weigh himself, mark the figure on a graph, and sign the process charts again after he had done his homework, washed his hands and face, and brushed his teeth. Mother wanted to have a place on the charts for saying prayers, but Dad said as far as he was concerned prayers were voluntary.

    It was strict management, all right. Yes, at home or on the job, Dad was always the efficiency expert. He buttoned his vest from the bottom up, instead of from the top down, because the bottom-to-top process took him only three seconds, while the top-to-bottom took seven. He even used two shaving brushes to make his face smooth enough, because he found that by so doing he could cut seventeen seconds off his shaving time. For a while he tried shaving with two razors, but he finally gave that up.

    “I can save forty-four seconds,” he complained, “but I wasted two minutes this morning putting this bandage on my throat.” It wasn't the injured throat that really bothered him. It was the two minutes.