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The unconscious and the smells

The unconscious and the smells

June 13, 2024

The trace of odors in the human unconscious

Like Gregory Samsa, Stephen D. woke up one day having undergone a metamorphosis. That morning, possibly due to the recent consumption of amphetamines, the smell took the reins of his entire perceptive world . And this was what defined this young man's life during the following days: an incredible sensitivity towards aromas. The exaltation of his smell made everything he noticed around him fragrant notes and, while retaining the rest of his senses, all seemed to have lost importance under the rule of the nasal.

For the first time, Stephen D. had the need to smell everything, identify people by their smell before seeing them and recognize the moods of their peers without looking at them. Not only did he become much more sensitive to all smells: all the layers of the real became powerful olfactory stimuli. In addition, this metamorphosis also meant entering into a reality in which a strong emotionality dyed everything , making the here and now come to the fore while the abstract thought dwarfed to dissolve in that rich range of sensations.


Unfortunately, after three weeks everything returned to normal. The loss of this gift, as abrupt as his arrival, and was a strong emotional blow. Once opened the door to a world of pure perception was difficult to give up those feelings.

These events, narrated by Oliver Sacks in a chapter called The dog under the skin, are presented as true by the author (Sacks, 2010/1985). However, to most of us this could seem like an almost alien story, something that has little or no relation to our daily experience. In general, we believe that smell is something like the poor brother of the five senses . This is true up to a point.



Smell, emotionality and unconscious

All our life seems to have audiovisual format : both our leisure time and the people with whom we relate and the situations in which we are involved are defined by what we can see and hear. However, the story of Stephen D. has a particularity that questions this rule: this young man increases his sensitivity to smells due to the effects of a drug, but the large structures of his body do not undergo any transformation.

Neither his nose is enlarged nor his brain transformed into that of a dog, and the changes appear and disappear very quickly, suggesting that they are due to a relatively superficial alteration. Simply, your nervous system works differently for three weeks on the brain mechanisms that already exist.

Perhaps everything is explained because, in the case of Stephen, some processes that normally remain unconscious came to make the leap towards consciousness. Maybe, even if we do not realize, we all have a dog under our skin, an unconscious part of us that reacts to odors beyond our control.


Scientific evidence seems to support this perspective. Today we know that the sense of smell is of crucial importance in our lives, even though we do not realize it. For example, it has been proven that odor is a potent trigger of memories associated with each of the fragrances, and that this happens regardless of our willingness to remember something. In addition, the experiences that the scents bring us to memory are much more emotional than the memories evoked by images or words (Herz, R. S., 2002). This happens with a wide variety of smells.

However, it may be that the most interesting repertoire of reactions we have to the smell is when that smell comes from another human being. At the end of the day, the information that other people provide us is as important, if not more so, than that which can provide us with a mature pear, cut grass or a plate of macaroni. If we want to understand how communication between people works based on smell, we have to talk about pheromones and of smells signature .


Invisible communication

A pheromone is a chemical signal emitted by an individual and alters the behavior or psychological disposition of another individual (Luscher and Karlson, 1959). They are chemical signals defined by each species in particular and that produce instinctive reactions. Smells signature, on the other hand, serve to identify each specific member of the species and are based on the recognition of odors previously experienced (Vaglio, 2009). Both occur everywhere in many forms of life, and the case of humans does not seem to be an exception.

Although the human species is not as sensitive to odors as other mammals (a sample of this is that our nose has flattened drastically, leading to fewer olfactory receptors), our body is able to know aspects of other people such as his identity, his emotional state or other aspects of his psychology from these "traces" that we are leaving through the air.

For example, in a 2012 study it was proven how people can get to be emotionally synchronized through the smell they emit. During the experiment, a number of men were exposed to two types of film: one of them was scary, and the other showed repulsive images. While this was happening, samples of the sweat of these participants were collected (in general, it must have been a very disturbing experience). Once this was done, these samples of sweat were exposed to a group of women volunteers and their reactions were taxed: those who smelled sweat segregated during the vision of the fear film showed a facial gestures associated with fear, while the language of the face of those who smelled the rest of the samples expressed disgust (de Groot et al, 2012).

Despite this, it is possible that the most important property of these odor traces is their ability to influence our reproductive behavior. The olfactory acuity in both men and women increases when reaching puberty (Velle, 1978), and in the case of women this ability to perceive smells fluctuates with their menstrual cycle (Schneider and Wolf, 1955), so the relationship between sexual behavior and smell It is obvious. It seems that men and women judge the attractiveness of people in part because of their smell, because it provides relevant information about the internal state of our bodies, an area over which sight and hearing can not contribute much (Schaal & Porter, 1991).

Women, for example, seem to tend to prefer couples with a repertoire of immune responses different from their own, perhaps to breed offspring with a good list of antibodies (Wedekind, 1995), and they are guided by smell to receive this type of data. Beyond the search for a partner, in addition, mothers can differentiate the signature smell of their babies two days postpartum (Russell, 1983). Babies, on their part, already from the first months of life are able to recognize their mother by smell (Schaal et al, 1980).


The explanation

How is it possible for smell to influence our behavior so much without our noticing it? The answer lies in the disposition of our brain. Keep in mind that the parts of the brain responsible for processing information about the chemical signals that surround us are very old in our evolutionary history, and therefore appeared much earlier than the structures associated with abstract thinking. Both the smell and taste are directly connected to the lower part of the limbic system (the "emotional" area of ​​the brain), unlike the other senses, which first pass through the thalamus and are therefore more accessible by conscious thought (Goodspeed et al, 1987) (Lehrer, 2010/2007).

For this reason the chemical signals that we receive through the nose act drastically on the emotional tone regulation , even if we do not realize it, and that's why smells are a unique way to affect the mood of people even if they do not realize it. In addition, since the hippocampus is included in the limbic system (a structure associated with memories), the signals collected by the nose easily evoke experiences already lived, and they do so accompanying this memory with a great emotional charge .

All this means, of course, that theoretically some type of handling about the rest of the people without them being able to do much to control their own feelings and psychological dispositions. The clearest example of this principle of manipulation is found, of course, in bakeries. Let's hope that the big television and computer manufacturers take a little longer to discover it.

Bibliographic references:

  • de Groot, J. H. B., Smeets, M.A.M., Kaldewaij, A., Duijndam, M.J.A. and Semin, G.R. (2012). Chemosignals Communicate Human Emotions. Psychological Science, 23 (11), pp. 1417-1424.
  • Goodspeed, R. B., Gent J. F. and Catalanotto, F. A. (1987). Chemosensory dysfunction: clinical evaluation results from a taste and smell clinic. Postgraduate Medicine81, pp. 251-260.
  • Herz, R. S. and Schooler, J. W. (2002). A naturalistic study of autobiographical memories evoked by olfactory and visual cues: testing the Proustian hypothesis. American Journal of Psychology, 115, pp. 21 - 32.
  • Luscher, M and Karlson, P. (1959). "Pheromones": a new term for a class of biologically active substances. Nature, 183, pp. 55-56.
  • Russell, M. J. (1983). Human olfactory communications. In D. Müller-Schwarze and R. M. Silverstein, (Eds.), Chemical Signals in Vertebrates 3. London: Plenum Press.
  • Sacks, O. (2010). The man who confused his wife with a hat. Barcelona: Anagram. (Originally published in 1985).
  • Schaal, B., Motagner, H., Hertling, E., Bolzoni, D., Moyse, R. and Quinchon, R. (1980). Les stimulations olfactives dans les relations between l'enfant et la mere. Reproduction Nutrition Development, 20, pp. 843-858.
  • Schaal, B.and Porter, R. H. (1991). "Microsmatic Humans" revisited: the generation and perception of chemical signals. Advances in the Study of Behavior, 20, pp. 474-482.
  • Schneider, R. A. and Wolf, S. (1955). Olfactory perception thresholds for citral using a new type of olfactorium. Applied Physiology, 8, pp. 337-342.
  • Vaglio, S. (2009). Chemical communication and mother-infant recognition. Communicative & Integrative Biology, 2 (3), pp. 279-281.
  • Velle, W. (1978). Sex differences in sensory functions. Psychological Bulletin, 85, pp. 810 - 830.
  • Wedekind, C., Seebeck, T., Bettens, F. and Paepke, A. J. (1995). MHC-dependent mate preferences in humans. Proceedings of the Royal Society of London B, 260, pp. 245-249.

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