Sadly, can't have dogs now, but my cats are extremely good at cold reading my intentions to snatch them up for a dose of flea preventer or to take them to the vet.
Sometimes, the older sister is wrong and hightails it when I'm only going to close the door or give her a scratch on the chin. The younger sister is just generally skittish, so it's harder to tell with her.
I've tried to pay attention to my behavior, and I've actually been able to notice (and correct) some "tells".
But you know, it's really no more amazing than a skilled poker player's ability to read opponents and make what appear to be miraculous calls and lay-downs.
Certainly, when my intent is to grab a cat, there must be differences in my physical attitude, even when I'm pretending that I'm not angling for a capture.