There is plenty of literature in the fear management/education genre that more or less breaks down "fear" origins into genetic (primal) or learned (conditioned). I think there's lots of validity in those two categories, although I do not believe they are fully adequate to cover the more sublime phenomena and territory of fear origins. I have been carefully observing one of my own interesting "fear" experiences for several years now, and it has arisen only significantly as I have got much older, in early-60s is when it began. I think this blog speaks to issues in feariatry.
The fear experience I am speaking about is one that comes spontaneously out of the unconscious, and although it has no doubt some genetic and learned components, I would say it is unique in that it comes from within the dream state, when I am sleeping or very near sleeping (some call the hypnogogic). For e.g., last night I was deep in a dream of having sex and it being very pleasurable and I was very concentrated, yet relaxed, and suddenly with no clues or stimulus from within the dream narrative itself, my entire body jolted and woke me up, my heart rate jumped and I realized I was having a fear/startle experience that seemed to have no obvious cause at all. I listened intently and heard no follow-up real sounds in the awake state. I even got up and checked out all the windows to see if there were any prowlers trying to break in as maybe I heard a bang--that was my first intuition of why I bolted up from the dream/sleeping state. But nothing was there. I saw a white-tailed prairie hare feeding on the front lawn of the yard and it was totally relaxed and that cued me that there was nothing unusual going on in the real world, nor did a loud noise actually happen. My mind had made it up. That was my conclusion.
As I say, I have had this rather disconcerting phenomena for several years now, which I don't remember having when I was young. Sometimes, I am certain in the bolting up from sleep/dreaming state that a gun shot or bang took place. Obviously threatening stimuli potentially. But no, my inspections after had me concluded that no such noise actually happened, but rather my mind made it up, and from what I can tell it did so without any external stimuli or material from within the dream itself that would warrant such a powerful fear/alert response. The whole experience can also sometimes include fairly loud voices of people, even somewhat distinguishable with words, but usually not. This is what might be called "hearing voices" that many psychiatric patients will talk about. These spontaneous productions are from the unconscious reservoir and what I would call the primal state below any dream narrative/imagery, etc. They literally seem to be illusions. They can totally fool my body into their "reality" and enough so to totally give me a fear/startle reaction with all the physiological equipment going into full gear. It takes me only 20-40 sec.'s usually to pull down the heart rate and calm down but they are strong enough illusions of "realness" to make me check out my environment in the house, again, often checking for burglars or some other event that is unusual and could be dangerous to myself or to others (e.g., neighbors).
So, it is a kind of hyper-vigilance that is interrupting my sleep/dream states at times, and even more disconcerting is when I am only falling asleep and in that trance where the unconscious can throw these stimuli forward and a fear/startle with it that is amazing to me how it can produce this effect. I see why many people can get very freaked out with this kind of spontaneous unconscious experience which seems able to flood all other brain activity, even a sleeping calm body. Why does it do this when there is, as far as I can tell in my analyzing these experiences, no external or internal stimuli that I am aware of? And, because i watch and listen and record my dreams as a regular practice I do well remember usually what I was dreaming at the time of these spontaneous irruptions. So, I can say confidently, there was no imagery in the dream or semi-dream state (hypnogogic) that produced the high arousal of danger. Equally, but a little less confidently, can I say, there was no external stimuli in the environment at the time that was producing the arousal I experienced so suddenly.
The WHY question remains, and I have this morning come up with a hypothesis that there are parts of the brain/mind/body system that are involved as source of these experiences I've been having. They could be from old (if not traumatic) circuits in the nervous system/tissues, that "replay" and "practice" both a threat and response to a threat, and these experiential loops of rehearsal and 'working through' seem to operate virtually on their own accord without any obvious reason coming from the physical environment or dream imagery and narrative--they have an independence. It is this latter trait, that verges on what could be called a mini-psychotic episode. Because I have lived with an x-spouse and worked with a few clients over the years who have psychotic experiences, my hypothesis seems reasonable and I also know how there can be this weird (if not subtle terror) that one is 'losing their mind' because of the information and experiencing going on in the aroused state that seems to have little to no cause that one can pin down as empirical or rational. Now, my experience of this min-psychotic 'break' is very minor compared to what some people I have seen go through when the flooding of material (e.g., loud sounds, voices, etc.) is highly intense and doesn't let up and it exhausts the fear-response system--and all other rational control systems as well.
I share this to record and highlight what may be more common than people (so-called 'normals') may experience but don't report to others nor even give it the time of day to reflect upon. I am a fearologist and I like to make notes on these phenomenon for research purposes, but also to make sense of what is happening to me. In the hypothesis I present, I think it is useful (less terrifying) so suggest that I am not 'losing my mind' (and ability to keep in touch with reality) but that my primal fear-system is rather "practicing" now and then as like going to the gym to build up its skills in "helping" me when any real situation of threat comes along, no matter of how subtle. So, in this meaning re-frame, rather than believe maybe I am going psychotic, I prefer to explore the meaning of "practice" and that indeed, I (my ego) is not in control of the "practice" and "working out" that is going on. And, I am learning to be okay with not being in complete cognitive control of all my functions, especially the Defense Intelligence systems (e.g., like the fear/startle response). On the other hand, I will say, that in my analysis of these spontaneous irruptions and illusions I experience now and then, there is always a bit of cognitive linking that I am able to do as to possible causes of such an irruption based on something I saw on TV in a glance or heard of as bad news, or as dangerous somewhere in the world. No doubt, I am linked by "matrixial strings" to these irruptions that are real in the physical and psychical world of people somewhere, or even animals and plants... and, I maybe just attuning in the dream/sleeping state to those matrixial relationships and having an empathic experience. I don't want to rule that out as an explanation either.