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Prey and Predator: Illustrations of the Fear System in action

Much of what I write about concerns the human Fear System – our biological response to threat.   Where it functions as it was designed to – switching on when danger threatens, and switching off when we are in a place of safety – then all is well with us.  However, where it malfunctions, particularly where it fails to switch off when it is not needed, it has a huge impact on us, and is perhaps the key underlying cause of most physical and mental ill health.

In this post I want to look at three video examples which vividly demonstrate the Fear System in action.

I am using the overall description of “Fear System” to cover 3 responses to danger or threat.  The first is the initial response of being alert to danger – going very still, holding the breath, trying to locate the source of danger.  The second, once the danger is clearly perceived, is fight-flight, where the sympathetic nervous system triggers a powerful and sudden physical mobilisation to escape from the danger, and the third, when the danger is too close for escape, is tonic immobility, a bodily shutdown triggered by the parasympathetic nervous system, that can switch off a predator’s attack and open up the possibility of a last ditch escape, or render death less fearful and painful.

Our Fear System evolved over countless millenia in the crucible of one animal’s need to catch and eat another.   I want to comment on three examples available on You Tube of prey and predator, which show various aspects of fight-flight and tonic immobility.

In the first example (click here)  we see fight-flight in action as a springbok is chased by a cheetah.   The springbok runs until it is caught, then puts up a fight until it is hopeless, then collapses.   The collapse is tonic immobility in action – the heart rate and blood pressure have plummeted – the animal is effectively in a faint.  The video then cuts to the aftermath of another chase where a cheetah has caught an impala. We see its limp body being dragged along by the cheetah, then lying on the ground as if lifeless, with its eyes still open – it is also in a state of tonic immobility.  At this point the cheetah is chased off by baboons.  Then the camera comes back to the impala – it still seems lifeless, but the camera focuses on a slight movement of the nostrils then a deeper breathing which moves the whole body.   At this point the camera angle shifts and it’s hard to see what’s going on, but in fact the impala is shuddering.  This is a release of the energy of fight-flight which was interrupted by the immobility collapse, and, along with the deep breathing is the natural way the body “resets” after major threat and is a key part of the mechanism by which the Fear System switches off.  We then see the impala standing up – it does not need to run away as it is already in a safe place with the protection of the troupe of baboons. 

In the second example (click here) a leopard has already caught an impala which is lying as if lifeless, eyes open, with its nose in the leopard’s jaws.   A hyena is spotted and the leopard is distracted – notice how, when the cheetah releases its grip to look at the hyena, the impala’s head flops onto the ground.  The “tonic” bit of tonic immobility refers to the fact that in this bodily shutdown, the muscles lose their “tone” or tension – hence the flop.  (There is a huge amount of confusion in the literature over the use of the word “freeze” being applied to this state, and tonic immobility being muddled with “rigid immobility” – a totally different biological state.  I will go into that when I write separately about Freeze)

The leopard is then further distracted by a couple of baboons which chase it off.    The implala is lying completely still at first, then its abdomen moves as it starts breathing deeply, and you can see some movement of the eyelids.  Then as it starts to right itself it shudders for almost a full minute, resolving into more gentle trembling – this is the “resetting” of the fear system referred to in the first example, but much more visible.  Finally the impala is up and away.  

In the third example (click here) we see another impala in fight-flight mode, and then collapsed, having been brought down by a cheetah.    The cheetah, exhausted by the chase, is itself chased off by a hyena.   However, as the cheetah and hyena face off against each other, the impala suddenly comes out of tonic immobility and makes off at high speed.  (ignore the narrator’s uninformed “cunning dissimulation” comment).    This is a good example of the “window of opportunity” that can open up after an immobility collapse, prompting a sudden switch out of immobility and back into fight-flight.  With both cheetah and hyena still on hand, this is not a safe place, but the energetic escape will burn off the energy of the fight flight response, and the fear system will switch off once a safe place has been reached. 

So the first two examples show a recovery from tonic immobility in what is now a safe place (protected by baboons), where there are a number of deep spontaneous breaths which expand the abdomen, followed by a period of shaking or trembling in which the tension and energy of the fight-flight impulse is dissipated  (effectively “resetting” the fear system).   The third example shows a window of opportunity for escape opening up in an unsafe setting, where there is a sudden switch out of immobility and back into fight-flight.

If you find this interesting, I would recommend reading Peter Levine’s book, In an Unspoken Voice. The first chapter gives an account of his experience of being hit by a car and shows how the same biological responses occurring in animals when a predator attacks its prey,  operate in us as humans when we face major threat.

Depression – a biological response to threat?

Published in Counselling Matters, (the magazine of the National Counselling Society) August 2022.

What do we know about depression?  We can list its symptoms such as low mood, low energy, a slowing of thought and movement, loss of concentration, and loss of pleasure and interest in activities.  There is also a disruption of our patterns of appetite and sleep, negative, hopeless, and sometimes suicidal thoughts, and a loss of both the ability and desire to socialise with others. 1     But what exactly is depression?   I am going to argue that it is a normal biological response to threat which has become “stuck”. 

Our human nervous system can respond to danger and life-threat in two key ways.  The first is by going into fight-flight, a state of heightened metabolic arousal. The second is by means of a bodily shut-down brought about by a sudden metabolic collapse. 2     This two-fold “threat response system” can be best understood by looking at the context in which it evolved – one animal’s need to catch and devour another, and the prey animal’s need to stay alive.   

When a predator attacks its prey, the prey goes into a state of highly aroused running or fighting to help it escape.   However, if this fight-flight response fails, an older threat response shuts down the body and the prey collapses, as we can see when a cat catches a mouse.   This collapse, which is the same biological mechanism as a faint3, stops the predator’s attack and can lead to a window of opportunity for escape if, for example, the predator has to fight off competition.  If such an escape route opens up, there is a sudden metabolic switch from collapse back into fight-flight4.   Then, if a place of safety is reached, the prey animal can rest and relax, and the threat response system switches off.

This threat response, which I refer to as our “Fear System”, evolved in the context of relatively brief attacks and chases5, but where the danger lasts too long or there is no place of safety that can be reached afterwards, the fear system becomes dysfunctional and is unable to switch off, and, as a result, fight-flight or shutdown reactions to any level of threat, whether real or imagined, become habitual6.   As humans evolved as intensely social animals, for whom expulsion from the group was a life-threatening danger, this fear system was wired-up to react to social threats, such as rejection, bullying or loss of status, with metabolic arousal or collapse, in the same way as if they were physical attacks7.   

I am proposing that this threat-induced collapse is the biological mechanism underlying depression.   Such a theory could clearly explain the experience of depression.  The metabolic collapse is brought about by a drop in heart rate and blood pressure8 that disables energy production by starving cells in every part of the body of the glucose and oxygen they need to function9.  This means muscle cells stop working, and our limbs feel heavy as lead.  Lack of understanding has stigmatised depression sufferers by treating energy loss as if it was just imagined.  This theory points to the physical (biological) reality of energy loss in depression.   

It would also explain many of the other symptoms of depression, as this shutdown de-energises brain cells, so we can no longer concentrate, or think clearly, and what thinking capacity remains is negative and hopeless.    The same de-energising of brain cells in the cortex deactivates our social engagement system10, so we lose both the desire and the ability to relate socially to others.  Unsurprisingly, we therefore lose all sense of pleasure in life. 

This theory raises the question as to why depression does not normally present as the full physical collapse seen in prey animals when they are caught by the predator.  I think the answer to this lies in our social engagement system which has developed to powerfully control our fear system responses (thus making social life possible).  However, where the fear system has become chronically stuck, and can’t deactivate, the ability of the social engagement system to control fear responses becomes impaired.  I think this impairment is the underlying cause of depression which can be seen as a metabolic collapse that has been partially but ineffectively controlled by the social engagement system11.  Thus, there may be “gradations in reactions to life threat” 12 so that the threat-based shutdown can be experienced not only as a full physical collapse, but also at lower levels of intensity, in the same way as we can experience a full faint, and also various levels of “feeling faint”.

Seeing depression as a stuck form of bodily shutdown would explain why it is so often experienced alongside anxiety, which can be viewed as a stuck form of the fight-flight response.  Where the overall threat system cannot switch off, these are the two most common states in which we are trapped.  Some people are affected predominantly by anxiety, others by depression, but many oscillate between both.

We see from the context of prey and predator that one way out of bodily shutdown is back through fight-flight.   When psychological therapists help people to get in touch with anger that has previously been inaccessible, they are helping them to reconnect with the physical sensations of fight-flight which can trigger a raising of mood. 13

However, the key factor in switching off the overall threat response system is safety14.  This system can only switch off if we can find safe places in which we can relax.  In a world of increasing poverty, zero-hours contracts, over-monitored employees, government-created “hostile environments”, over-tested schoolchildren, collapsing care services and fear-driven and polarised politics, safe places where we can truly relax are disappearing, and unsurprisingly, levels of anxiety and depression are rising.   

As a sense of safety depends on the contexts in which we live and work, this theory suggests that depression is not some sort of “defect” in the individual sufferer but arises from a normal biological response to threat. However, if there is insufficient support to enable us to return to a sense of safety in the aftermath of a threat, or we live in contexts where threats are unrelenting, the threat response cannot deactivate, and will manifest as anxiety and depression.

Michael Guilding                                                                                        

Notes

  1. American Psychiatric Association. (2000) Diagnostic and Statistical Manual of Mental Disorders. Fourth Edition, Text Revision. Washington, DC, American Psychiatric Association. p.356
  2. Porges, S. W. (2017) The Pocket Guide to the Polyvagal Theory; The Transformative Power of Feeling Safe, New York, WW Norton & Co Inc., pp. 53-56
  3. Porges, S. W. (2017)  pp.10-11.
  4. Levine, P. (2010).   In an Unspoken Voice: How the Body Releases Trauma and Restores Goodness, Berkeley, North Atlantic Books.  pp. 47-50
  5. Sapolsky, R.M. (2004). Why Zebras don’t get Ulcers (3rd Ed.), New York, Holt Paperbacks.  pp.154-5. (When flight-fight is activated, the immune system increases activity for about 30 minutes then drops back to normal levels by about one hour.  If stress continues beyond this point, the immune system is impaired, compromising the ongoing defence of the body.) 
  6. Levine, P. (2010) p. 19-30, 54
  7. Sapolsky, R.M. (2004).  pp. 355-383
  8. Van der Kolk, B. (2014). The Body Keeps the Score. London, Allen Lane. p. 82
  9. This process is very clearly explained in Myhill, S. (2014).  Diagnosis and Treatment of Chronic Fatigue Syndrome. London, Hammersmith Health Books. pp. 20-24
  10. The biological system involved in sending and receiving signals of safety which enable us to engage with each other without activating defensive responses.  Porges, S. W. (2017)  p.26.
  11. Guilding, M. (2020). What is Complex Trauma?  Perspectives on Trauma. The Journal of the Complex Trauma Institute,Volume 1, Issue 1, pp. 3-18. 
  12. Porges, S. W. (2017)  p.12.
  13. Agazarian, Y.M. (2004). Systems Centered Therapy for Groups, London, Karnac.  p. 203. See also Levine, P. (2010) pp. 73-95. and Ogden, P., Minton, K., Pain, C. (2006)  Trauma and the Body:  A Sensorimotor Approach to Psychotherapy,  New York, WW Norton & Co Inc. pp.186-187
  14. Porges, S. W. (2017) pp.xv-xvi.

For a fuller account of the thinking behind this theory, see the article “Rethinking Depression“