They can, according to K9 officers' partners I've heard. When they're on the hunt for a suspect who is running on foot and hiding somewhere, a K9 officer can actually follow the scent being put out by the suspect and locate him.
Adrenaline is a very potent hormone and when us human type folks are excited or fearsome tend to have this realesed in our bodies.The result is an odor of this coming through our pores and anyone with a nose the size of an ear of corn can pick up on this,it's not sensing fear but just something that gets them excited as well...just my opinion.
I think Lola can. Today I walked into my bedroom to find my cell phone antenna chewed. She chewed the tip off and the plastic base of the antenna where it connects to the phone. She had it completely off.
She must have heard me coming because I found her under the bed so she knew she did wrong.
I guess in this case the fear that she smelt was her own.
I don't know if they can smell it or not, but I think they can pick it up. If we humans can pick up on whether someone is fearful or not and the dog has senses that far exceed our own they can surely pick up on it too.
There are dogs being trained/are trained to smell out cancerous cells amongst healthy ones. There are many stories of dogs picking up on cancer in patients LONG before they realized they had it--their dog would poke at the spot, etc.
I'm fairly sure that if they are capable of differentiating such tiny secretions put out by cancerous cells, they can smell the hormone changes that take place in the body of someone who is afraid, etc.
Honestly, I think dogs, and cats both (well, most animals really) can sense fear, anger, you name it, in humans.
I groom dogs, and cats, for example. My husband, baths, on occasion for me. There are some dogs and cats, that will 'lash out irrationally' at him for no apparant reason, other than they seem to know he is afraid of them. When I go to pick them up, on the other hand, they show no anxiety, or threatening jestures. I think they just know who is afraid of them; I am not one of them!
I groomed a cat today, that one of the other groomers said is absolutely terrible; bites, claws...is just plain MEAN! Well...she hissed a few times, but other than that, I had NOT an ounce of trouble from that kitty...I figure it is mainly the demeanor difference between the other groomer and I; I am really calm, and will take my time and not subject the cats to extras (like the hi vo dryer), that tend to upset the cat further. I also don't raise my voice when they get 'loud' or 'viscous'...she does (saying "Stop that" or "Quit"), and I don't understand that...it's not like it accomplishes anything, other than further aggrivating an already finicky critter!Lol!