ArmoredSkeptic said on a recent video about ghosts that:
EM fields actually trigger our fight or flight response
Is that true?
It may be helpful to look at different regions of the EM-spectrum one by one to attempt an answer.
The spectrum ranges from static fields, over very low frequency and radio waves to high and ultra high frequency fields, equivalent to photons of very high energy.
A rough overview:
static electric fields: some animals, such as sharks, have fine tuned sensors that detect the very weak fields created by other animals. Humans can only feel static electric fields if they have very high intensities (think your hair standing off when touching shift voltage generator). This may trigger some response, though (as far as I see) no immediate fight or flight.
static magnetic fields: again, humans do not have sensors for them
low frequency fields up to radio waves: no sensory in humans, no fight or flight.
high frequency fields, as used by cellular phones: no sensory in humans. It is disputed (and considered unlikely) that these have adverse effects on the human health, in any case, they do not cause fight or flight response. The associated photons have too low energy to excite any molecules in the human body, however, very high intensity fields cause some amount of local warming in the body due to absorption.
infrared light: contains enough energy to excite molecules. This is the radiation warmth you feel coming from a heater or a fire. (You may consider for yourself under which conditions this triggers “fight or flight”).
visible light: can excite molecules, e.g. in your eyes:-) Can obviously cause fight or flight. Then again, why not just say “flash of light” instead of “EM-field”? I guess this is not what the video was talking about.
higher energy than visible light: UV, X-rays, gamma radiation. Can cause huge damage to the human body, but no fight or flight (this makes radiation damage so treacherous).
Summary: fight or flight may occur for those regions of the EM-spectrum where the human body has some form of sensors (e.g. your eyes reacting to light). But then, you would probably not call that an "EM-field".