Deep-fried foods are tastier than bland foods, and children and adults develop a taste for such foods. Fatty foods cause the brain to release oxytocin, a powerful hormone with a calming, antistress, and relaxing influence, said to be the opposite of adrenaline, into the blood stream; hence the term "comfort foods." We may even be genetically programmed to eat too much. For thousands of years, food was very scarce. Food, along with salt, carbs, and fat, was hard to get, and the more you got, the better. All of these things are necessary nutrients in the human diet, and when their availability was limited, you could never get too much. People also had to hunt down animals or gather plants for their food, and that took a lot of calories. It's different these days. We have food at every turn ― lots of those fast-food places and grocery stores with carry-out food. But that ingrained "caveman mentality" says that we can't ever get too much to eat. So craving for "unhealthy" food may actually be our body's attempt to stay healthy.

Do you advise your kids to keep away from strangers? That's a tall order for adults. After all, you expand your network of friends and create potential business partners by meeting strangers. Throughout this process, however, analyzing people to understand their personalities is not all about potential economic or social benefit. There is your safety to think about, as well as the safety of your loved ones. For that reason, Mary Ellen O'Toole, who is a retired FBI profiler, emphasizes the need to go beyond a person's superficial qualities in order to understand them. It is not safe, for instance, to assume that a stranger is a good neighbor, just because they're polite. Seeing them follow a routine of going out every morning well-dressed doesn't mean that's the whole story. In fact, O'Toole says that when you are dealing with a criminal, even your feelings may fail you. That's because criminals have perfected the art of manipulation and deceit.

It seems natural to describe certain environmental conditions as ‘extreme', ‘harsh', ‘benign' or ‘stressful'. It may seem obvious when conditions are ‘extreme': the midday heat of a desert, the cold of an Antarctic winter, the salinity of the Great Salt Lake. But this only means that these conditions are extreme for us, given our particular physiological characteristics and tolerances. To a cactus there is nothing extreme about the desert conditions in which cacti have evolved; nor are the icy lands of Antarctica an extreme environment for penguins. It is lazy and dangerous for the ecologist to assume that all other organisms sense the environment in the way we do. Rather, the ecologist should try to gain a worm's-eye or plant's-eye view of the environment: to see the world as others see it. Emotive words like harsh and benign, even relativities such as hot and cold, should be used by ecologists only with care.

Petroleum is the "blood" of industry. But as it is buried deep in the earth, how can we find it? Sometimes, considerable labor, materials, and money are spent without exactly identifying the distribution range of petroleum. Here, bacteria can be said to have a mysterious bond with petroleum. Petroleum is composed of various organic compounds, of which the majority is a carbon and hydrogen compound called hydrocarbon. Although petroleum is buried deep, there are always some hydrocarbons coming up to the earth's surface through the gaps in rock formations. Gas components in petroleum can also leak to the surface. Some bacteria feed on petroleum. Therefore, when explorers detect a great amount of such bacteria in a place, they know there is probably petroleum. On the basis of the quantity of bacteria detected in the sample, they can also predict the quantity of petroleum and gas in reserve.

In spite of thousands of research studies, we are still unclear on the most basic question ― What is the function of sleep? The most obvious explanation is that sleep is restorative. Support for this idea comes from the observation that species with higher metabolic rates typically spend more time in sleep. A less obvious explanation is the adaptive hypothesis; according to this view, the amount of sleep an animal engages in depends on the availability of food and on safety considerations. Elephants, for instance, which must graze for many hours to meet their food needs, sleep briefly. Animals with low vulnerability to predators, such as the lion, sleep much of the time, as do animals that find safety by hiding, like bats and burrowing animals. In contrast, vulnerable animals that are too large to burrow or hide ― for example, horses and cattle ― sleep very little. In a study of 39 species, the combined factors of body size and danger accounted for 80% of the variability in sleep time.

Tap your finger on the surface of a wooden table or desk, and observe the loudness of the sound you hear. Then, place your ear flat on top of the table or desk. With your finger about one foot away from your ear, tap the table top and observe the loudness of the sound you hear again. The volume of the sound you hear with your ear on the desk is much louder than with it off the desk. Sound waves are capable of traveling through many solid materials as well as through air. Solids, like wood for example, transfer the sound waves much better than air typically does because the molecules in a solid substance are much closer and more tightly packed together than they are in air. This allows the solids to carry the waves more easily and efficiently, resulting in a louder sound. The density of the air itself also plays a determining factor in the loudness of sound waves passing through it.

Most people fear many things, both great and small, and though we may never have to face up to our worst nightmares, few of us are unfamiliar with the sweaty palms and parched lips that are typical physical accompaniments to the emotion of fear. Fear is not, of course, a pleasant sensation, and it often impedes our acting in the ways we think we ought to. For those reasons, we might consider that humankind would have been better off if endowed with a literally fearless nature. But that would be a big mistake. For frail and vulnerable creatures like ourselves, a disposition to feel fear is a vital evolutionary acquisition, since it prompts us to take care of ourselves in situations of danger. Those who feared nothing would dare anything; and the consequences would all too often be disastrous. Fear, it is true, sometimes applies the brakes too sharply to our efforts; but it is better to possess brakes that are occasionally over-effective than to have no brakes at all.

Monkeys sleep on branches high in the forest canopy. This certainly keeps them safe from ground predators such as leopards and jaguars, but it must be unstable and uncomfortable. The monkeys sit on as thick a branch as they can find, resting their weight on pads of skin that develop on their buttocks, but even so they repeatedly wake up throughout the night. An ape, sleeping within a broad, cup-shaped nest, is far safer and can sleep for longer periods and more deeply. Studies by David Samson, now at the University of Toronto, and his coworkers, comparing neural activity in sleeping monkeys and sleeping apes, have shown that the apes have more frequent periods of both NREM (non-rapid eye movement) and REM (rapid eye movement) sleep. These types of sleep are important in reordering and fixing memories, which can in turn help improve cognitive ability. Building nests could have helped apes get even cleverer.