Many of us have experienced the following: the day before an exam, we try to squeeze a huge amount of information into our brain. But just as quickly as we acquire it, the knowledge we have gained is gone again. The good news is that we can solve this problem. With expanded time intervals between a person's learning events, we keep the knowledge for a longer time.

But what happens in the brain during the spacing effect? It is generally thought that during learning, neurons (经经元) are activated and form new connections. In this way, the learned knowledge is stored and can be regained by reactivating the same set of neurons. However, we still know very little about how pauses positively influence this process.

Neurobiologists Annet and Pieter did an experiment, during which mice had to remember the position of a hidden chocolate piece in a maze (迷宫). On three continuous chances, they were allowed to explore the maze and find their reward—including pauses of different lengths. "Mice trained with the longer intervals between learning phases (阶段) were unable to remember the position of the chocolate as quickly," explains Annet. "But the next day, the longer the pauses, the better was the mice's memory."

"If three learning phases follow each other very quickly, we naturally expect the same neurons to be activated," Pieter says. "After all, it is the same experiment with the same information. But after a long break, we imagine the brain interprets the following learning phase as a new event and processes it with different neurons."

However, the researchers found the opposite. In fast continuous learning phases, the mice activated mostly different neurons. When taking longer breaks, the same neurons active earlier were used again later. Reactivating the same neurons could allow the brain to strengthen the connections between these cells. With spaced learning, we may reach our goal more slowly, but we benefit from our knowledge for much longer.

If you have trouble falling asleep, listen up. You might fall asleep 15 minutes earlier and wake up far less during the night if you put on a pair of socks at bedtime. To understand why, you first need to grasp the relationship between core（核心）body temperature and sleep. During daylight hours, the human body has an average temperature of 37℃. But your core body temperature drops as much as 1. 2°℃ over one night's sleep. This gradual decrease is a key part of how we sleep. To put it simply, the faster you can lower your core body temperature, the faster you will fall asleep.

One way that your body controls its temperature is through blood vessels （血管）in the skin. If your body is too hot, your blood vessels widen, pushing the warmer blood nearer the skin' s surface, helping it to cool. If your body is too cold, the opposite happens. Your blood vessels narrow, restricting the flow of blood to the surface.

The soles, the bottom surface of your feet, are one of your body's most efficient heat exchangers, since they are hairless and less protected than other skin surfaces. Researchers have shown that warming the feet before going to sleep using a warm foot bath or by wearing socks promotes blood vessel widening, which in turn lowers the body's core temperature faster than going to sleep with cold, bare feet.

Scientists suspect that socked feet have a neurological effect as well. The warm-sensitive neurons（神经元）in the brain become more active when there's a temperature difference between the body's core and the feet. Researchers have found that these neurons become more active as we get sleep and slow down as we wake up, so that warming up the feet before bedtime may give warm-sensitive neurons an extra promotion, making you feel sleepier.

In a small study, researchers found that wearing a pair of special "sleeping socks" not only sped up the coming of sleep, but increased overall sleep time by an average of 30 minutes and cut night-time waking times in half. If you're worried about becoming too warm, look for socks made of natural fibers.

Recently I bought a book about signposts.  Signposts aren't very interesting, you're thinking. Well, that, of course, depends on whether you happen to be lost! Ancient travelers would have been grateful for these when settlements were smaller and further apart. In winter, the ability to reach shelter for the night could be the difference between life and death. 

One of the very earliest waymarks discovered is in Cumbria. Dating from Roman times, it had lain fallen until 1836, when a farmer ploughing his fields came across a sandstone shaft(碑文). There are other stone posts that have stood by roadsides for centuries. It wasn'tuntil 1697 that an act was passed declaring that guide-stones must be built. 

This applied to remote parts of the country where there might be confusion as to which path led to the nearest market town. Later, with the appearance of the Royal Mail, the number rose still further. Nowadays many of these early road signs are designated(指定)as Listed Monuments. 

"How times change!" Lucy, an enthusiastic walker, to whom I loaned the book,exclaimed. 

"I suppose now we all rely far more upon mobile phones to guide us. "

"Yet they aren'tperfect. Whenever I go out, I prefer a map. I never have to worry about running out of battery. " "T'm always grateful to whoever is placing way-markers along the route," she added,"I suppose that however sure we are, a little outside confirmation is always welcome. "

Lucy is quite right there. Life itself can offer us a great many choices of path, and sometimes it isn't easy to know if we've chosen the best one. 

Perhaps when it comes to gratitude, we should also include thanks for those people who appear in our lives when we most need them—either giving us gentle warning that we might be heading in the wrong direction, or reassurance that we are on the right track. After all, we'd be lost without them!