You're a generous person (or not)
I make judgments about you based on your actions. University of Milan researchers had dogs watch some people sharing food with a beggar and other people telling the beggar to leave. Later, when the individuals beckoned the dogs at the same time, the pups overwhelmingly trotted over to the generous people. Your pets also know these other secrets about you.
You don't like someone
When you have negative feelings about a person, I can hear your breathing pattern change, observe your body stiffen slightly, and even smell the subtle pheremones your body emits. So if your in-laws suspect that I don't like them, it may simply be because, um, you don't really like them. (Make sure you always follow these summer safety tips for your pooch.)
Where you've been
You humans are like sponges. You pick up volatile organic compounds from everything you walk by or touch. If you just visited, say, the supermarket, I will smell the butcher and fish counters, the food you bought, and maybe even the people you stood next to at checkout. I can smell something 100 million times more subtle than the faintest smell you can pick up. Read the inspiring stories of these heroic dogs that saved their owners.
You may have cancer
Some of us are being taught to detect different types of cancer by smelling certain chemicals that cancer cells can emit. In some studies, we were 88 percent accurate in detecting breast cancer, and 99 percent accurate in detecting lung cancer. These are signs that your dog is sick.
You're coming home
We've learned your schedule, and we know roughly when to expect you back at the house each day. But even if you an get home at an odd hour, I can pick out the sound of your particular car coming down the street, and I am always listening for it.
You've had a fight with your spouse
Even if you don't yell in front of me, I may notice your clipped tone of voice, the fact that neither of you is speaking, the stiffness of your posture, or the agitated way you're walking or opening drawers. Some of us get sick to our stomachs when our owners are bickering.
You need protection
Do I sleep cuddled up next to your bed instead of in my usual spot when your spouse is out of town? Do I stay closer to your leg than normal when we walk through a dark area? I can smell the adrenaline your body releases when you're scared, and I'm also more vigilant anytime someone in the household is missing.
You're going on a trip
I hate it when you leave, so I've learned to pick up on all the clues when a departure is imminent--suitcases pulled from the closet or the way you always spread clothes out on your bed. Some of us start to shake and pant because our anxiety spikes. Feel bad? One study found playing classical music for us when we're alone can help us calm down. This is how you can keep your pet busy when you're away from home.
You're a sucker for our puppy dog eyes
Researchers have found that your body releases the hormone oxytocin (the same chemical that's released when you look at your baby) when we make eye contact with you. So there's a reason we gaze at you lovingly when we want something: It works.
What your intentions are
I can pick up nearly imperceptible signals in your body language--a darting of your eyes or the way you grab the leash--that tell me what you're planning. In one study, dogs were easily able to identify the location of hidden food simply by following a human gaze.
You're not feeling well
We can be trained to sniff out everything from a drop in your blood sugar to a migraine. A growing number of epileptic patients are getting dogs that alert them to a seizure before it happens. In one Hawaiian hospital, dogs sniffed out urinary tract infections in paralyzed patients who couldn't report symptoms.
Your baby is weak
I know your little one is a member of my pack, and I also know she's the most vulnerable. Because I have a strong instinct to guard my family members, I can be extremely protective. That's why I bark aggressively when someone approaches the stroller and why you should be vigilant if someone is playing with your child while I'm around. (If I mistakenly think she is getting hurt, I may attack.)
You're bummed out
I am a master at reading your body language and emotional state. One study found that I can tell if someone's sad simply by reading facial expressions (even if I'm looking at a photo of just half a face!). I'm also more likely to approach someone who is crying than someone humming or talking, an indication of empathy.
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