Ch 1 L7: smell, the first step to learn

    1. Our extremely slow and meticulous analysis of the first experience on the Earth [1] has yet to conclude. So far, we’ve experienced the thing [2], then we realized that our first reaction should be to feel fear [3]. Given the fact that our confidence level is zero [4], we’d go for the flight response; however, it’s very theoretical because, during the short experience, we hadn’t detected any motion (change); so, we instinctively found it harmless [5].  Here comes another question, how certain can we be?

The Thing

      1. Right now, we can’t even analytically think about the thing; however, to scratch this moment, we can say that our brain has been collecting data, even for the fraction of a second, based on which it decided to call it probably not dangerous. This experience lays the egg of two intertwined branches of mathematics: statistics and probability [6] which we’re gonna exhaustively discuss later.
      2. The drive to find sources of energy [7] which makes us approach things around us is called curiosity. So, we cautiously move towards the thing. However, the uncertainty still keeps us anxious; therefore, we need more information to have a more accurate judgment which can be expressed by the raised eyebrows and dilated pupils to collect more light. As you know, this reaction is called surprise [8,9]


      1. So far, the level of fear hasn’t reached the threshold of fight-flight response. Everything seems to be normal, no strong stimuli. Suddenly your nose sends some signals to the brain. you have detected some smell.
      2. knowing the fact that some bacteria can respond to chemical changes in their environment which can be roughly considered as the first sign of smelling, the olfactory system could be considered the first evolved sense. We vitally need to react to chemical changes because, in some situations, we instantly die, say, if we breathe in toxic air.
      3. The outcome of the analysis is translated into emotional reactions. we find it either good or bad (like or dislike it) which can be somehow correlated with life and death [10]. It’s very important to know that nothing has any natural good or bad smell which is our assessment of an experience: what we find stinky or pungent is often dangerous to our health [11,12].
      4. The same judgment goes with taste; we find sugar, carbs or other nutritions palatable, because of the amount of energy and the molecular components our body needs and is able to digest [13].
      5. It shouldn’t be surprising why we relate a disgusting behavior or incident to gustatory experience and our facial expression would be the curled upper lips and wrinkled nose or as Darwin observed: to close the nostrils against a noxious odor or to spit out a poisonous food. [14]
      6. The olfactory system has two advantages over the other senses:
        1. It’s one synapse away from the limbic system, so we react to smell faster than visual or auditory signals. [15]
        2. we don’t need to touch or taste things to evaluate them. In other words, it can be done from a relative distance.
      7. The sense of smell even contributes to the pleasure of eating more than the taste. When you smell a delicious food, it activates dopamine, a happy hormone released by reward. Interestingly, researchers have shown that it’s released earlier while anticipating a reward. So, thanks to our nose, the pleasure of eating even starts before the first bite. Besides, you also don’t feel much of taste, if you can’t smell it [16].
      8. We react to other’s smell as well. Our brain can detect dominance and fear from pheromones. An amazing fact about our brain and what’s going on subconsciously is it can distinguish someone’s fear from their smell. A group of researchers collected the sweat of two groups: ones who sky-dived (an indicator of fear) and the other who ran. Then they asked people to smell them and find the difference. The participants didn’t find any difference. but the MRI of their brain showed that two different parts of their brains were activated. So, the brain could distinguish the difference between the smells [17,18].
      9. A mesmerizing yet tragic portrait of the power of smell is in the movie “Perfume: the story of a murderer” [19] based on the novel “Das perfum” [20] which explores the relationship between smell and emotions. Spoiler alert: you can skip the rest of the paragraph if you’re interested to watch it. The protagonist kills 12 girls to capture the smell of their dead body (from their sweat) which would be the essence of the mythological smell that could bring down the scent of paradise. I haven’t read the book but I watched the movie which I strongly recommend you. I can talk about the metaphors in the movie but it might spoil your experience.


Exercise 7:

      1. I read on the Internet that if you chewed a gum with a new flavor while studying a topic, then chewed the same flavored gum on the exam, you’d more easily remember the content. What do you think about it?
      2. Another idea to think: there are special chemicals in different types of toothpaste which tingle your tongue and gums. They don’t help with the cleaning at all, but they give you the feeling that your teeth are cleaned. [21]


[1] Again I recommend you to start from the first lesson if you’re interested to follow the story. Link to the first lesson.

[2] Link: P. 19.

[3] Link: P. 33.

[4] Link: P. 37.

[5] Link: P. 52.

[6] That’s why these two subjects go hand in hand because for every decision, we need to collect data and we also need to consider the chance that it fails.

[7] Link: P. 6.

[8] Again for more information, you can refer to Emotional Intelligence by Daniel Goleman.

[9] As we’ve discussed fear is the dominant feeling to which we’ve related the existence of all other feelings. Now we saw that surprise is nothing but mild fear. But the anticipation of reward (energy) releases dopamine which makes us excited as well. It depends on one’s history that experiencing new things brought joy or pain.

[10] Link: P. 16.

[11] We might like the taste of a food though it’s very smelly. Then after a while, the smell doesn’t bother us, and we might even like the smell.

[12] Another factor to evaluate a smell is its familiarity which we discuss later. For instance, you might find people from other ethnicities or countries smelly mainly because their natural smell is different than yours.

[13] our body needs minerals but processed by plants. Some people who suffer from lack of minerals especially iron might start eating soil which is called geophagia which is not digestible.

[14] Again for more information, you can refer to Emotional Intelligence by Daniel Goleman.

[15] Since the limbic system is in charge or learning and long-term memory, similar smells can easily bring back childhood memories.

[16] It happens especially when you catch a cold, so your nose gets blocked and you can’t smell anything.

[17] You can find more information about the smell in prof. Sapolsky’s lectures at Stanford: “Behavioral Biology“.

[18] The factor of smell can affect the way that we’re attracted to people; we may find them more attractive and that’s what the perfume industry is working on.

[19] Link

[20] Link

[21]  Link to “The Power of Habit”

*The pictures are respectively taken from:



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