We may fear the same thing that our parents do, especially if we feel, to put it literally, their fear – because it has a distinct smell and it can be inherited. Jowita Kiwnik Pargana talks to Jacek Dębiec, a psychiatrist at the University of Michigan.
As a psychiatrist, Jacek Dębiec specializes in the therapy of fear and trauma; as a scientist he researches, among other areas, the smell of fear. I would like to find out if we really can sense someone’s fear and if its smell may cause our fear. I also want to understand what the mechanism of transferring fear from one generation to another consists of.
Jowita Kiwnik Pargana: What is the smell of fear?
Jacek Dębiec: Fear is passed on through olfactory stimuli that we wouldn’t refer to as smell. By smell, we usually refer to something that we can consciously sense: the smell of food, flowers, a meadow, a forest. The smell of fear is a combination of many smells. For example, when we are frightened, the level of stress hormones rises and we sweat more. This also contributes to a different smell of our body. In the animal world, fear is also communicated through pheromones. Research suggests that they can also play a certain part in transferring fear between humans, but we don’t experience them consciously, as they are odourless for us. Pheromones stimulate the nervous system, causing specific inner states. We can only realize the outcome of this stimulation – for example, a feeling of fear.
Does this mean that the smell of fear from others can also affect us?
Ways of communicating fear have been shaped by millions of years of evolution. For animals living in groups, communicating about a life-threatening danger is essential for survival. If an individual notices a predator, it is in the interest of the whole group to quickly warn all of its members so that they can react by, for example, running away or hiding. Let us imagine a herd of antelope. If an antelope sees a creeping or attacking lion and starts to run, the others automatically start to run in the same direction, without even looking towards the predator. There is no time to stop and check calmly if the danger is real, because the most important thing is to keep the herd alive. Information about the threat may be conveyed through visual stimuli (e.g. the sight of horror in others, or through voice). The loud screaming of frightened animals – often referred to as the ‘primal scream’ – conveys a message about danger and mobilizes others to escape. This doesn’t only operate among the same species of animals, but also among others. For example, monkeys can react to the screaming of birds that warn about an approaching predator. The smell of fear can also alert others about a threat.
In your research, you proposed an interesting hypothesis: that progeny can be afraid of the same thing as their mother, all they need to sense is her smell of fear.
And this hypothesis was proven. In our research, female rats were subjected to mild electric shocks. Mild, because the aim wasn’t to cause pain, but to frighten them a little bit. Similar research is also conducted on humans. During the time when the rats were subjected to an unpleasant stimulus, the space in which they were in was filled with a peppermint scent, which normally doesn’t cause any fear in them.
I suspect that the female rats started associating the smell of peppermint with the anticipation of something unpleasant?
Yes, after such conditioning the animals started showing signs of fear in their reaction to the peppermint scent. Frightened rats usually freeze, their heart beats faster, their blood shows increased levels of corticosterone (a steroid that is the equivalent of human cortisol). Several weeks after this experiment, we left female rats in cages with male rats. After a while, they got pregnant and gave birth. Then we sprayed the peppermint odour into the room in which the female rats and their offspring were kept; the mothers reacted with fear. It is hard to measure reactions in pups, as they do not have fully developed senses after birth. They are born with membranes over their eyes and ears, so they can neither see nor hear. But they have a very good sense of smell. After some time, when the offspring grew a bit and were separated from their mothers, we checked how they reacted to the peppermint odour. It turned out that the pups displayed fear, just like their mother had done earlier. The conclusion of these experiments is that the mother’s reaction to the peppermint scent in her children’s presence creates fear in them in response to the same smell.
Are you confident this is about the smell?
First of all, we established that the reaction was not transferred through congenital factors, such as genes or epigenetic changes, as we also observed similar reactions in the case of foster mothers. Therefore, we put forward the hypothesis that since the pups cannot hear their mother’s vocalization, nor can they see her when she reacts to stress – when she freezes in response to the peppermint scent – then perhaps she communicates this fear to them through smell. In the following experiments, we separated the mothers from the pups. We gave mint to the mothers to stimulate fear in them and then we pumped the mixture of the smells of a frightened mother and mint into the room with the pups. That was enough for them to start feeling afraid, too. If, on the other hand, the mother wasn’t frightened and we mixed her ‘usual’ smell with the peppermint scent, the pups weren’t afraid. Further research by other scientists from Japan and Canada led to isolating the pheromones responsible for fear in rats and mice. It was found that exposure to these compounds evokes a fear reaction, and when they are combined with other stimuli, such as a specific smell or sound, they can also evoke fear, even though initially the animals didn’t react with fear to these stimuli.
Yet we are talking about research on animals. Can these results be applied to humans?
Similar experiments have also been carried out on human beings. For example, volunteers were given to smell the T-shirts of people who had just seen a horror film. It was established that their smell evoked reactions pointing to a heightened level of stress. In other experiments, researchers selected people with a fear of heights and asked them to climb a climbing wall, which obviously evoked fear in them. Simultaneously, the control group was cycling and not experiencing any stress. Later, researchers compared the reactions of research participants to the smell of the T-shirts of those who were afraid and those who only exercised. Interestingly, the volunteers weren’t able to consciously differentiate between the smells. However, research using fMRI showed that the smell of people who were afraid activated the amygdala, which in our brains is responsible precisely for the fear reaction. Of course, human reactions to the smell or pheromone of fear are not as intense as those displayed by animals. There is no evidence that anyone would, for example, start running away in panic as a reaction to the mere smell of fear. However, the level of discomfort certainly increases.
In your publications, you claim that fear might not be genetically inherited, but rather transferred from one generation to another. How?
Some stimuli evoke in us natural fear reactions. It is the result of hundreds of millions of years of evolution. If we hear a scream of terror, we experience stress – we don’t have to learn it. Loud thunder nearby usually evokes anxiety in us. Danger was an inherent feature in our ancestors’ lives for millions of years and the fear of danger had significance for the survival of the species. Yet there are also stimuli that we learn – for example, fear of the dentist. We certainly don’t acquired this through evolution, although some people react fearfully to a dentist visit because it often involves pain.
Let’s imagine that a child has never been to a dentist before and has had no bad experiences in a dental room. Can the child simply adopt this fear from a parent or a carer?
Science suggests that it can. There is a process called instructional learning, meaning learning through instruction. In the context of learning fear, it is a situation where a parent simply says: “It is dangerous, be afraid of this.” Yet, fear is very often transferred simply through a parent or carer’s reaction. Therefore, if they are afraid of the dentist, they can transfer it onto their child.
It usually takes place when a child observes its parent’s fear reaction to a specific situation. The parent doesn’t even need to say that she or he is afraid, but the voice timbre becomes more nervous, she or he holds the child tighter and behaves in a way that indicates the experience of fear. The child reads these emotions and unconsciously associates their occurrence with the context. Let us imagine that a young girl was once brutally attacked in a park, somehow she managed to overcome this trauma, but when she walks through the park, not always aware of it, she walks faster, looks around, the fear reactions are released within her. Now let us imagine that 10 or 15 years later, the same woman walks with her child through the park. The traumatic memory isn’t present in her consciousness, but when she enters the park, she walks faster and holds the child’s hand tighter. In this way, the child learns unconsciously that the park is a dangerous place that the mother is afraid of. And the child also starts feeling afraid. There are many situations like this one. There are whole communities and nations traumatized by the war experience.
You also work with the adult children of those who survived the Holocaust. Many of them have had nightmares associated with the Holocaust, even though it took place before their birth. How is this possible?
The interest of clinicians in the children of Holocaust survivors started when therapists began to work with young people – the offspring of the survivors – and the young people described reactions that we would currently understand as part of post-traumatic stress disorder. They suffered from, among others, night terrors in which they saw scenes from concentration camps, round-ups or street executions. They also had sudden, intrusive and frightening imaginings of Holocaust events. It was as if they had lost touch with reality and entered the world of imagination.
I understand that these people heard about war experiences from their parents, but did it happen that, to a certain extent, they took over their parents’ trauma?
They learnt to be afraid of the same things that evoked fear in their parents. Yet this is not only about the transfer of trauma, as in instructional learning, but about imitation. People who have experienced great trauma, such as the experience of a concentration camp, very often experience permanent epigenetic changes, meaning changes in the structure of DNA. The changes can also affect the sensitivity or the number of receptors associated with stress hormones. This increased susceptibility to stress may be passed onto successive generations. This is not just about remembering certain situations, but about restructuring the whole system responsible for our defence reactions.
People with PTSD often overreact, and they might treat a neutral stimulus as if it was connected with danger. A person who survived World War II might, for example, start fleeing when they hear someone speaking German.
In his book I Blame Auschwitz, Mikołaj Grynberg talks to the adult children of Holocaust survivors. Some of them didn’t know for many years about their parents’ experiences during the war, but they still experienced fear and pain for some reason. Can we assume that their parents had transferred that fear onto them unconsciously?
I think so. If a human being survives an apocalypse, they might not have the words to describe it. Besides, very often we try to suppress these experiences into a corner of our minds and never go back to them. We don’t do this consciously, but they are still within us evoking incessant fear. The experience of horror or great trauma doesn’t only affect an individual, but also his or her surroundings, because the person senses and experiences fear in the presence of close family. We are talking about the Holocaust, but such traumas as a car accident or domestic abuse evoke similar reactions. It is an extreme example, but let us imagine a mother who as a young woman experienced rape. Her daughter doesn’t know what her mother experienced; the mother isn’t psychologically ready to talk about her experiences, or she isn’t able to talk about them. Yet she can react with fear to certain situations. She panics when her daughter goes to a party or on a date. The daughter doesn’t realize why the mother behaves in this way, but at the same time her mother’s fear becomes her own.
But we don’t all react in the same way, do we?
We differ when it comes to our reactions to stress. Some people are naturally more resilient and others less so. It might be connected with the levels of stress system reactivity. A lot depends on whether, following an incredibly stressful or frightening event, we receive support that allows us to build a sense of safety, or if we end up in a social vacuum and remain with our experiences on our own.
Is it possible to prevent the generational transfer of fear?
Yes, but it might be difficult in some cases. You need to notice the problem, realize it and work on rebuilding your own level of safety so that the risk of unintentional contamination of children with fear is reduced.
We already know that our sense of smell allows us to sense fear. But does it allow us to ease it as well?
Of course. In the case of those species that, following birth, stay for a long time with a parent or carer, they are dependent on the parent and develop a relationship with them – most often the parent becomes a synonym for safety. I am saying ‘most often’ because life can turn out differently. This is why in later life the sound of the parent’s voice, their presence or exact smell can reduce fear and provide a sense of safety. We often carry photos of our close family in our wallets because they offer us a soothing feeling of their presence. Fear can also be reduced by other stimuli – for example, a memory of our childhood room, our favourite toy, flavours remembered from our childhood, the melody of a lullaby. The stimuli that we associate with the safety of a family home – if, of course, it was safe – are remembered by us for the rest of our lives and we can bring them back to ease the sense of fear.
Parts of this interview have been edited and condensed for clarity and brevity.
A child and adolescent psychiatrist, professor at the Department of Psychiatry at the University of Michigan in the US. He specializes in trauma and PTSD therapy, as well as treating perinatal psychological disorders.
Translated from the Polish by Agata Masłowska
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