A dog can be a person’s best friend, or so the theory goes. But that relationship can be tested when a dog begins barking at an empty comer of a room, at a door, or anywhere where there doesn’t appear to be any activity at all taking place. Is the dog hallucinating? Is it communicating with ET? Or does it simply want to drive its owner crazy?

According to the American Kennel Club, the most common explanation for dogs’ barking without reasons is that it’s not really unprompted at all. Dogs are, obviously, equipped with superior hearing, including the ability to detect sounds that are higher in pitch. It is said a dog could be reacting to a noise that a person wouldn’t be able to hear. If a dog barks seemingly for no apparent reason at night, it might be because the noise nearby is lessened and some barking of other dogs become more clearly. Because dogs are territorial, one dog barking can turn into many others to guard themselves.

Dogs are also able to see better in the dark than humans thanks to their ability to get more light into their retinas (视网膜). If a dog is reacting to what looks to you like an empty backyard at night, it’s possible that something has caught their attention, be it a wild animal, a leaf, or a stranger.

That’s not to say that dogs only bark because of their cute senses. Some dogs might bark out of boredom in which case more exercise or play time is probably needed. They might also be trying to get their owner’s attention.

The AKC recommends that owners avoid scolding their dogs for barking, since they’re simply trying to remain alert, instead, you can try calming the dog to let them know you’re aware of their concern. If they tend to bark while gazing out a window, you can also try to pull the curtains. If you suspect the source is an audio cue, some white noise, like a television or radio can help.

Less often, chronic barking might be a sign of cognitive issues. If barking is persistent and no fugitive is hiding out in your bushes, then you might consider a trip to the vet.

Dogs are much smarter than people imagine. A new study has even shown that they will ignore (忽视)us when they know that we are lying to them. They can even tell when strangers are lying to them when it comes to food.

The study tested if dogs could use clues in order to tell whether people were being honest on not. The study found that in certain cases, dogs are able to understand when someone is lying

Of course, the main interest for dogs is food, which is how researchers tested this theory. They gathered 260 dogs of different kinds. The researchers found that dogs were able to follow their own sense when they were given wrong instructions about where the food actually was

The dogs were given two boxes and were taught to follow the advice of a human they did not know in order to find the treat. The human tapped the box with the treat while looking at the dogs and saying “look, this is good.” By following this advice, they got the treat

Next, the dogs watched as a second human they did not know changed the box the treat was in, at times while the first human was still there, and sometimes while he was not. Half the dogs did not follow the human’s advice if he was not present while the change happened, meaning the dogs knew the fact that he did not know where the treat was. Interestingly, two thirds of the dogs were able to refuse the advice from the humans pointing to the wrong box when they were there for the change, which shows that the dogs knew that they were being lied to, the opposite of what researchers were expecting.

The researchers said that in earlier studies, both young children and primates (灵长类) were more likely to follow the advice of the lying person, though they saw the truth, suggesting that dogs are less trusting humans’ advice.

Overheating is a serious issue for birds flying long distances, and paler feathers that reflect more of the sun's heat may be one of the ways they cope.

The latest study of nearly all of the 10000 or so bird species has found that the farther birds migrate (迁徙), the paler their feathers tend to be. This is probably because it helps birds flying in sunlight to keep cool, says Kaspar Delhey at the Max Planck Institute for Ornithology in Seewiesen, Germany. “Feather colour is extremely diverse and many factors can drive the evolution of colours, of which migration is only one.”

Several recent studies suggest that overheating is more of a problem for birds flying long distances than previously thought. For instance, sensors have shown that the body heat of migrating eider ducks can rise so high that they have to stop flying.

Another study found that some migrating birds fly much higher during the day than they do at night, despite having to spend more energy staying high in thinner air. This suggests that the heat of the sun makes them much more likely to overheat, and made Delhey and his colleagues wonder whether migrating birds have lighter feathers to help them cope.

The researchers used photos from the Handbook of the Birds of the World to rate the lightness of birds' feathers from 0 to 100, treating males and females as separate species because colour is so often different between the sexes. They found that short-distance migrants were significantly lighter than birds that didn't migrate, and long-distance migrants were significantly lighter than short-distance migrants, even without taking into account factors such as body size or the environmental conditions where birds live.

One possible result of the phenomenon is that migrating birds are going to find it even harder to stay cool as the planet heats up. Rising temperatures may force darker species to fly only during the night while migrating, says Dellhey, or to fly even higher during the day. These responses will probably involve costs, which may reduce individual survival, with potential negative consequences at the population level, he says.