Regardless of how real the stress may or may not be, when our brain perceives a situation as being threatening, the process it engages is the same. Just like airport security, our brain has to take every situation seriously because failure to identify threats could be disastrous.
Therefore, whenever we encounter a stimulus, whether it is a bear, a highway full of slow-moving cars, or a traveler who for some reason chose to wear shoes, the first thing our brain has to do is determine if that stimulus is going to kill us. It is a very high-priority decision that the brain has to make before we take any other action. I am sure I don’t have to explain to you why it is so important that our brains do this.