Hospitality means the relationship between a guest and a host, where the host receives the guest with goodwill, including the reception and entertainment of guests, visitors, or strangers. Louis de Jaucourt describes hospitality in the Encyclopédia as the virtue of a great soul that cares for the whole earth through the ties of humanity.

Hospitality originated (起源) from the Latin hospes, which means “stranger” or “enemy”. In the West today hospitality is rarely a matter of protection and survival and is more related to politeness and entertainment. However, it still involves showing respect for one’s guests, providing for their needs, and treating them as equals. It is expected to show hospitality to strangers, rather than to personal friends or members of one’s ingroup.

In ancient Greece, hospitality was a guest’s divine right, with the host being expected to make sure the needs of his guests were met. The ancient Greek term xenia, or theoxenia when a god was involved, expressed this ritualized (仪式化的) guest-friendship relation. In Greek society a person’s ability to obey the laws of hospitality determined nobility and social standing.

In India, hospitality is based on the principle “the guest is God”. This principle is shown in a number of stories where a guest turned out to be a god who rewards the provider of hospitality. From this originates the Indian practice of graciousness towards guests at home and in all social situations.

Celtic (凯尔特人的) societies also valued the concept of hospitality, especially in terms of protection. A host was expected not only to provide food and shelter for his/her guests, but to make sure they did not come to harm while under their care.

Grandparents who help out occasionally with childcare or provide support for others in their community tend to live longer than seniors who do not care for other people, according to a study

The findings are drawn from data on more than 500 people over age 70 in the Berlin aging Study. The participants completed interviews and medical tests every two years. Overall after considering grandparents age and general state of health, the risk of dying was one-third lower for grandparents who cared for their grandchildren, compared with grandparents who didn’t provide any childcare.

Half of the grandparents who cared for grandchildren were still alive ten years after the initial interview. The same was true for participants who did not have grandchildren but supported their adult children in some way, such as helping with housework. In contrast about half of the participants who did not help others died within five years after the start of the study.

“Caregiving may be thought also as an activity that keeps caregivers physically and mentally active, said Professor Arpino, adding that previous studies suggest that caregiving may improve cognitive functioning, mental and physical health.

Arpino noted, however, that caregiving is not the only activity that can improve health, and too many caring responsibilities can take away benefits from other activities like working, being in social clubs, or volunteering.

“Children should take into account their parents' needs, willingness, and desires and agree with them on the timing and amount of childcare," Arpino suggested.

A quick increase of dopamine (多巴胺) shifts mice into a dreamy stage of sleep. In the mice’s brains, the chemical messenger triggers rapid-eye-movement sleep, or REM, researchers report in the March 4 Science.

These new results are some of the first to show a trigger for the shifts. Understanding these transitions in more detail could ultimately point to ways to treat sleep disorders in people.

Certain nerve cells in the ventral tegmental area of the mouse brain can pump out dopamine, a molecule that has been linked to pleasure, movement and learning, which is then delivered dopamine to the amygdalae, two almond-shaped structures deep in the brain that are closely tied to emotions.

Using a molecular sensor that can tell exactly when and where dopamine is released, the researchers saw that dopamine levels rose in the amygdalae just before mice shifted from non-REM sleep to REM sleep.

Next, the researchers forced the mice into the REM phase by controlling those dopamine-producing nerve cells using lasers and genetic techniques. Compelled with light, the nerve cells released dopamine in the amygdalae while mice were in non-REM sleep. The mice then shifted into REM sleep sooner than they typically did, after an average of about two minutes compared with about eight minutes for mice that weren’t prompted to release dopamine. Stimulating these cells every half hour increased the mice’s total amount of REM sleep.

Additional experiments suggest that these dopamine-making nerve cells may also be involved in aspects of narcolepsy (嗜睡症). A sudden loss of muscle tone, called cataplexy, shares features with REM sleep and can accompany narcolepsy. Stimulating these dopamine-making nerve cells while mice were awake caused the mice to stop moving and fall directly into REM sleep.

The results help clarify a trigger for REM in mice; whether a similar thing happens in people isn’t known. Earlier studies have found that nerve cells in people’s amygdalae are active during REM sleep.

Many questions remain. Drugs that change dopamine levels in people don’t seem to have big effects on REM sleep and cataplexy. But these drugs affect the whole brain, and it’s possible that they are just not selective enough.