Experts talk of the development of brains, from "reptilian" to "mammal' to "primate/human". From early reptilian times, apparently for about 300 million years, the reptilian brain has reacted more-or-less automatically to external stimuli. According to the experts, over many millions of years, brains evolved from simple/reptilian brains to more-sophisticated mammalian brains and finally to extremely-sophisticated human brains. [Nature's greatest creation]

Reptilian brains are considered to be primitive and reactive…illustrating a complete lack of social skills and limited by pre-set tendencies to freeze, fight, or flee.

Mammalian brains are capable of connection with one another. For example, wolves live in groups [packs], hunting together and to a degree serving one another.

Primates and particularly their elite – the humans – have much more elaborate social capabilities. We possess mirror neurons which allow us to have an understanding of others thoughts and emotions. And the human brain contains a large cortex, which allows, among other things, logical thought.

As human brains evolved the 'reptilian core' remained at the centre of things…reacting automatically to the wide array of fearful things presented by Mother Nature…freezing, fighting, and fleeing. In addition to these ‘natural’ reactions to the threats brought to us by Mother Nature, some of us [maybe all of us?], at least from time to time, also exhibit freeze/fight/flight reactions while we are interacting with our families in our homes and our coworkers in our offices. In these situations our reptilian brains can make our lives more complicated and stressful.

Fear is Mother Nature’s preferred method of motivation. [The experts are quire certain that reptilian responses worked well for a few hundred million years.]

Fear still motivates. [although I have argued against this in the past]

Fear motivates in ways that save our lives. [assuming we find ourselves in life threatening situations and react properly]

For some people in some situations, fear is countered by courage and heroic action follows. [...i.e., heroism is deemed an admirable response]

And, some people create plans that help them condition themselves against fears to they take themselves beyond normal physiological reactions. [as examples, Navy Seals and the Dalai Lama know how to go beyond freeze/fight/flight]

Regardless, we should not be confused about motivation and compete with the role of Mother Nature - we  should not behave in ways that inject fear into our workplaces. [Workplace fears rarely bring about constructive reactions.] 

People put up with Mother Nature when she brings fear. Perhaps, that’s because Mother Nature brings so many positive things to us? People have less tolerance of the fears brought to them by other people. At best, fear-mongering generates temporary positive action. 

PS: If you buy into Ralph Waldo Emerson's views on compensation...the fear you present to others will become the fear that, sooner or later, comes back to bite you. [and your reptilian brain will not appreciate the bites]