Horses are extremely intelligent, and their extra vigilance is just one of the many indicators that they are smarter than many of us realize.
They are not only able to learn how to respond to commands, horses are also able to recognize familiar people just by looking at their faces.
Horse intelligence is measured through scientific studies and experiments, many double-blind, so that the humans within the study do not inadvertently treat the animals differently.
Horses communicate with other horses all the time. Communication is key to help keep horse herds safe and alert horses will warn the rest of the herd of nearby predators.
Horses can recognize their owners, they can sense changes in human emotions, they have amazing memories, and they can communicate.