Read this article in 4 levels: Basic A1 (英検3級), Intermediate B1(英検2級), Advanced C1(英検1級), original version. Multiple choice content questions for each level. Free English reading practice. The more you read in English, the more your English will improve. Why do some things smell good and some things smell bad?
A1 Beginner 英検3級
B1 Intermediate 英検2級
C1 Advanced 英検1級
Original article
Basic A1 (英検3級) Version:
Article: Why do some things smell good and some things smell bad? Things smell good or bad because of what we learn and how our bodies have changed over time.
We smell things because everything around us is made of tiny parts called molecules. Some of these molecules go into the air, and when they reach our noses, they touch special parts inside called smell receptors. We have around 400 to 1,000 of these receptors. When a smell touches them, it sends a signal to our brains. Our brain puts all these signals together to understand the smell. This is like how we taste food and see colors.
The first reason we like or don’t like a smell is because we learn it. For example, some people love the smell of durian fruit because they grew up eating it, but others think it smells bad. We learn to like or dislike smells based on our experiences. If you enjoy cookies, you will think they smell good. But if you have bad memories of something, you may not like the smell of it.
The second reason is evolution. This means changes in our bodies over a long time. Long ago, we learned to avoid things that could make us sick. Bad smells often come from things like rotting food or poop. These things have harmful bacteria, so we learn to stay away from them. Some animals, like hyenas, eat rotting meat, so they like those smells. But most animals, like us, avoid them.
Questions:
- Why do we smell things?
a) We see them
b) Molecules enter our noses and touch smell receptors
c) We hear them
d) We taste them - How many smell receptors do we have?
a) 10
b) 100
c) 400 to 1,000
d) 5,000 - What is the first reason we like or dislike smells?
a) Our eyes
b) Learned experiences
c) Our ears
d) Our feet - Why do some people like the smell of durian?
a) They have eaten it before and like it
b) It smells like cookies
c) It is sweet
d) It smells like flowers - Why do we usually like the smell of cookies?
a) They are good for us
b) We learn that they taste good and have sugar
c) They look nice
d) They are healthy - What is the second reason we dislike certain smells?
a) Evolution
b) Because they are loud
c) Because they are colorful
d) Because they are cold - Why do we dislike the smell of rotting food?
a) It is safe to eat
b) It is dangerous and could make us sick
c) It is fun to play with
d) It is too colorful - Which animals like the smell of rotting meat?
a) Dogs
b) Hyenas and vultures
c) Cats
d) Birds - What do bad smells protect us from?
a) Good food
b) Nice things
c) Harmful bacteria and sickness
d) Toys - What happens if an animal evolved to dislike rotting meat but needed it to survive?
a) It would avoid it and find something else
b) It would enjoy it more
c) It would play with it
d) It would stop eating it
Answers:
- b) Molecules enter our noses and touch smell receptors
- c) 400 to 1,000
- b) Learned experiences
- a) They have eaten it before and like it
- b) We learn that they taste good and have sugar
- a) Evolution
- b) It is dangerous and could make us sick
- b) Hyenas and vultures
- c) Harmful bacteria and sickness
- a) It would avoid it and find something else
Intermediate B1 (英検2級) Version:
Article: Why do some things smell good and some things smell bad? The reason things smell good or bad is a mix of what we learn from experience and how we evolved over time.
We smell in the same way we taste. Everything around us is made of molecules, and some of these are released into the air. When these molecules enter our noses, they attach to smell receptors, of which we have about 400 to 1,000. Each receptor can respond to many different molecules. When triggered, they send signals to our brain, which combines the information to identify a scent, similar to how it recognizes tastes and colors.
One reason we like or dislike certain smells is that we learn to do so. Different cultures find different scents appealing. For example, durian fruit is loved by some because they grew up with it, but others find its smell unpleasant. Our brains link scents with experiences, which is why we might enjoy the smell of cookies but not of certain vegetables. Bad experiences can also make a pleasant smell seem bad.
The second reason is evolutionary. Our ancestors evolved to avoid smells associated with danger, like rotting food or excrement, which often contain harmful bacteria. These bacteria produce sulfur compounds, which have a strong, unpleasant odor. By avoiding these smells, humans avoided illness and had a better chance of survival. This response is common in many animals, but some, like vultures and hyenas, have evolved to seek out rotting meat because they can safely digest it.
Questions:
- How do we smell things?
a) By seeing them
b) By molecules attaching to smell receptors in our nose
c) By tasting them
d) By touching them - How many smell receptors do humans have?
a) 10-20
b) 400-1,000
c) 5,000-10,000
d) 100-200 - Why might someone dislike a smell that others find pleasant?
a) Because of a bad experience associated with that smell
b) Because it is unhealthy
c) Because it is noisy
d) Because it looks bad - Why do people in different cultures have different preferences for smells?
a) Because of different genes
b) Because they have learned to like or dislike certain smells
c) Because of different diets
d) Because of different weather - What is one reason we dislike the smell of rotting food?
a) It tastes bad
b) It contains bacteria that can make us sick
c) It is too colorful
d) It is too soft - What compound do harmful bacteria release that smells bad?
a) Oxygen
b) Sulfur compounds
c) Carbon dioxide
d) Nitrogen - Why did humans evolve to avoid bad smells?
a) To find food faster
b) To avoid dangerous bacteria and toxins
c) To run away from animals
d) To sleep better - Which animals are mentioned as seeking out the smell of rotting meat?
a) Lions and tigers
b) Hyenas and vultures
c) Dogs and cats
d) Bears and wolves - How do animals like vultures safely eat rotting meat?
a) They don’t smell it
b) They have strong stomach acid that neutralizes toxins
c) They cook their food
d) They wash it first - What helps link smells to memories?
a) The ears
b) The olfactory center of the brain
c) The eyes
d) The tongue
Answers:
- b) By molecules attaching to smell receptors in our nose
- b) 400-1,000
- a) Because of a bad experience associated with that smell
- b) Because they have learned to like or dislike certain smells
- b) It contains bacteria that can make us sick
- b) Sulfur compounds
- b) To avoid dangerous bacteria and toxins
- b) Hyenas and vultures
- b) They have strong stomach acid that neutralizes toxins
- b) The olfactory center of the brain
Advanced C1 (英検1級) Version:
Article: Why do some things smell good and some things smell bad? The reason things smell pleasant or unpleasant is a combination of learned experiences and evolutionary adaptation.
We perceive smells in a similar way to how we taste. All things are composed of molecules, some of which are released into the air. When these molecules enter our nose, they attach to olfactory receptors, of which humans have between 400 and 1,000. Each receptor is capable of detecting a wide variety of molecules. Once activated, these receptors send electrical signals to the olfactory center of the brain, which interprets them and constructs a scent profile, much like how our brain interprets tastes from our taste buds or colors from the cones in our eyes.
The first reason we find certain smells pleasant or unpleasant is based on learned associations. Cultural differences can lead to varying scent preferences. For instance, the durian fruit, which is appreciated in some cultures, might smell intolerable to those unfamiliar with it. Our brains associate smells with experiences, so if a scent is linked to a positive memory, it’s perceived as pleasant. Conversely, if a smell is tied to a negative experience, it can seem unpleasant.
The second reason is evolutionary. Our ancestors evolved to avoid harmful bacteria and toxins, many of which are associated with foul smells like those from rotting food or excrement. Bacteria responsible for decay often produce sulfur compounds, which humans find particularly offensive. This aversion helped our ancestors avoid potentially deadly toxins and illnesses. Over time, this trait became widespread, increasing the likelihood of survival. However, not all animals share this aversion. Scavengers like vultures and hyenas have developed strong stomach acids that allow them to consume decaying meat safely, so their evolution has led them to seek out, rather than avoid, these smells.
Questions:
- How do olfactory receptors in the nose work?
a) They reflect light
b) They attach to molecules and send signals to the brain
c) They only detect food
d) They filter air - What role does learned association play in our perception of smells?
a) It has no effect
b) It links scents to memories and experiences, shaping our preferences
c) It only affects our taste
d) It changes our sight - Why might someone enjoy the smell of a food that others find unpleasant?
a) They have different olfactory receptors
b) They grew up with positive experiences related to that smell
c) They can’t smell well
d) They see the food differently - How does evolution affect our response to smells?
a) It makes us attracted to all smells
b) It has led us to avoid smells associated with danger and disease
c) It only affects animals
d) It makes no difference - What types of compounds are often associated with foul smells from decay?
a) Water vapor
b) Sulfur compounds
c) Carbon
d) Helium - What is the evolutionary benefit of finding some smells offensive?
a) It helps us sleep
b) It encourages us to avoid harmful substances
c) It improves our eyesight
d) It makes us hungry - How do scavengers like vultures and hyenas differ in their perception of rotting meat?
a) They have no sense of smell
b) They seek out the smell of rotting meat because their bodies can handle it
c) They avoid the smell
d) They prefer fresh food only - How did humans likely develop an aversion to certain smells?
a) Through genetic mutations that offered survival advantages
b) Through learning from parents
c) From animals
d) By accident - What is one way the brain constructs a scent profile?
a) By detecting vibrations
b) By interpreting electrical signals from olfactory receptors
c) By feeling the temperature
d) By seeing colors - Why can some animals eat decaying meat safely while others cannot?
a) They are stronger
b) They have evolved strong stomach acids to neutralize toxins
c) They have no sense of taste
d) They cook the meat first
Answers:
- b) They attach to molecules and send signals to the brain
- b) It links scents to memories and experiences, shaping our preferences
- b) They grew up with positive experiences related to that smell
- b) It has led us to avoid smells associated with danger and disease
- b) Sulfur compounds
- b) It encourages us to avoid harmful substances
- b) They seek out the smell of rotting meat because their bodies can handle it
- a) Through genetic mutations that offered survival advantages
- b) By interpreting electrical signals from olfactory receptors
- b) They have evolved strong stomach acids to neutralize toxins
Original Version:
Article: Why do some things smell good and some things smell bad? The reason things smell good or bad is a combination of learned experiences and evolution.
We smell in the same way that we taste. Everything around us is made of molecules, and some of these molecules are released. If they happen to be released in the vicinity of us and find their way into our noses, they can attach to smell receptors that we have there. We have approximately 400 to 1,000 of these scent receptors, and they can each react to a multitude of different molecules. When they are triggered by a molecule, it creates an electric signal that travels to the olfactory center of the brain, and the brain works out what signals came from what scent receptors and puts together a scent profile from that. It is the same way our taste or sight works. With taste, we have taste buds that have receptors that get triggered by different molecules in the food. These signals go to the brain, and the brain analyzes how much of which taste came and puts together a total taste. It is the same with sight. We have cones in our eyes that detect red, green, or blue light. They send signals to the brain, and the brain works out how much of each color it has seen to make an overall color and an overall picture. Some things we taste are good, and some things we taste are bad. Some things we smell are good, and some things are bad. Why is that?
There are two main reasons. The first is a learned response, and this is why people in different cultures find different scents appealing. If you have never eaten a durian fruit and were exposed to one, you would not be able to eat it because of the smell. However, if you have grown up eating them and know that they taste amazing, you would associate the same smell with something that tastes good, and the smell would be pleasant to you. This is down to memory and learned association. We learn from an early age to connect the smells of things to the experience that comes with them. For example, most people think a cookie smells better than a salad because we have learned that a cookie has an instant hit of sugar and fats that our body wants. Scent and memory have a very strong connection, which you can see when you suddenly get a nose of a smell that reminds you of something that happened in your childhood. If you had a bad experience every time you ate a cookie, perhaps if you were strongly allergic to chocolate, you would probably grow up to dislike the smell of cookies. There are also, interestingly, some scents that we cannot detect. Oxygen is one of them. We have the ability to detect trillions of different smells, but we cannot smell oxygen.
The second reason is evolutionary. We have fairly strong stomachs and fairly strong stomach acid, but there are still bacteria and certain toxins that can make us very sick, or are potentially fatal. A lot of these bacteria release sulfur and oxygen (sulphate), which we have evolved to think smells particularly bad. These bacteria release this compound when they are decomposing things, such as old food, meat, bodies, and anything that is rotting. These bacteria are also present in excrement, making it smell bad. We have evolved to dislike these smells because if there is a smell we don’t like, we will avoid the source of the smell. That will stop us from eating rotten food, staying near dead bodies, or staying near excrement. Avoiding those things will keep us safe from the bacteria and their lethal toxins. There was probably a point where we didn’t think those things smelled bad, but a mutation meant that one organism started to dislike the smells and stayed away. That organism had less chance of getting sick and more chance of passing on its genes, so disliking the smell spread. Interestingly, the majority of animals avoid smells that come from rotting meat and dead bodies. However, there are some animals, such as hyenas and vultures, that live on decayed meat and have stomach acid that is strong enough to destroy even the hardiest of toxins. They haven’t evolved to dislike the smell of rotting meat because if they did, they wouldn’t be able to eat anything. On the contrary, they have evolved to seek out the smell.
Questions:
- How do we perceive smells?
a) By touching objects
b) By molecules attaching to smell receptors in the nose
c) By seeing colors
d) By hearing sounds - How many smell receptors do humans typically have?
a) 10-20
b) 400-1,000
c) 5,000-10,000
d) 1,000-2,000 - What is one reason we like or dislike certain smells?
a) It is always genetic
b) It is based on learned experiences
c) It is random
d) It depends on the weather - Why might people from different cultures have different scent preferences?
a) They have different genes
b) They have different diets
c) They have different learned associations with scents
d) They live in different climates - How does evolution influence our sense of smell?
a) It has no effect on smell
b) It helps us avoid dangerous smells associated with bacteria and toxins
c) It makes all smells pleasant
d) It makes us smell colors - Why do we find the smell of rotting food unpleasant?
a) It looks ugly
b) It contains bacteria that can make us sick
c) It is too spicy
d) It is too sweet - What kind of compounds do decomposing bacteria often release?
a) Helium
b) Sulfur and oxygen compounds
c) Carbon dioxide
d) Nitrogen - How does the human brain create a scent profile?
a) By combining signals from the olfactory receptors
b) By reading memories
c) By listening to sounds
d) By seeing colors - Why don’t some animals, like vultures and hyenas, avoid the smell of rotting meat?
a) They have no sense of smell
b) They have evolved to seek out the smell because they can safely digest decaying meat
c) They find it sweet
d) They avoid it, but have no choice - What is an example of a scent that humans cannot detect?
a) Water
b) Oxygen
c) Carbon
d) Iron
Answers:
- b) By molecules attaching to smell receptors in the nose
- b) 400-1,000
- b) It is based on learned experiences
- c) They have different learned associations with scents
- b) It helps us avoid dangerous smells associated with bacteria and toxins
- b) It contains bacteria that can make us sick
- b) Sulfur and oxygen compounds
- a) By combining signals from the olfactory receptors
- b) They have evolved to seek out the smell because they can safely digest decaying meat
- b) Oxygen
