Why can’t I help but stick my hands into rice when I go to the supermarket?

Have you ever had this experience: when you see bulk rice in the supermarket, you have a strong urge to put your hand in and feel the tingling and cool touch? The heroine Amelie in "Amelie" has such a habit. When no one is paying attention, she likes to put her hand in the pile of grain to enjoy the feeling of being wrapped.

Source: A clip from "Amelie"

If you have had such experience or imagination, then congratulations, you are not alone! In fact, many people have such a preference, and some even call it a "rice complex."

1. Skin pressure

There are many different kinds of receptors on our skin. When you insert your fingers into rice, the rice grains will exert a slight pressure on your fingers. This pressure will stimulate the pressure receptors on the skin, thereby producing a comfortable feeling.

This compression has a relaxing effect on the body, and is actually similar to the principle of the elastic stockings we usually wear or the pneumatic massage devices we use.

Source: Wenzhou Geriatric Hospital

Compression stockings use the pressure receptors on the skin. When pressure stimulates the receptors on the skin, electrical signals are generated. The electrical signals pass through the tertiary nerve fibers from the spinal cord to the thalamus and then to the cerebral cortex. After the cerebral cortex decodes the electrical signals, it can sense and locate the pressure, allowing the brain to regulate the contraction and relaxation of blood vessels, thereby improving the speed and direction of blood flow. Pneumatic massagers also use the pressure receptors on the skin. When the skin is under pressure from the airbag, it sends signals to the brain to release some neurotransmitters that can relieve pain and tension, such as endorphins and dopamine. Therefore, when we insert our fingers into the rice, it is like giving ourselves a massage. This massage can make the blood circulation in our fingers smoother and also allow our brains to release some substances that can feel comfortable and pleasant.

Source: Pexels

2 Thermal conductivity of rice

In addition to the pressure on the skin, there is another factor that affects the feeling of our hands inserted into the rice, that is, the thermal conductivity of the rice. The thermal conductivity of air is about 0.13 W/(m·K), while the thermal conductivity of rice is about 0.2 W/(m·K), which is at a medium-to-low level. **When our fingers are inserted into the rice, the rice will absorb a small amount of heat from our fingers, causing the temperature of our hands to drop slightly, so we will feel a cool feeling rather than a cold feeling. **In addition, rice is rich in starch, which can also make hands dry. The double cool feeling is a very comfortable experience for us in summer or hot environments, and it can also relax our mood.

3. The psychological effects of gripping

The "addictive" feeling of inserting your hand into the rice is also related to the grasping action. Grasping is a very basic human behavior and also a very important human behavior . This action has a certain impact on the psychological state. Clenching a fist or grasping an object can improve our memory.

Source: Baidu

A study conducted at the University of Toledo in Ohio, USA, found that when the test subjects clenched their right fist when learning some words, they could improve their memory, that is, their ability to remember the words; and when the test subjects clenched their left fist when recalling some words, they could improve their ability to recall the words.

Source: Instant Encyclopedia

The principle of this phenomenon is that making a fist can activate the motor cortex of the brain, and the motor-related cortex is closely connected to the area of ​​the brain that stores and calls up memories, so making a fist can promote the use of memory. The left hemisphere of the brain is responsible for reasoning and calculation, and is the "rational hemisphere", while the right brain is responsible for spatial imagination, empathy, and artistic creation, and is the "emotional hemisphere". The right hand is related to the left hemisphere of the brain, so making a fist with the right hand is conducive to perceptual cognition of words and connecting them with actual things through imagination, thereby enhancing memory; making a fist with the left hand strengthens the logical thinking ability of the human brain and calls up words that have been stored in the brain. Another interesting discovery is that grasping objects can improve our mood and self-confidence. A joint team from the University of Michigan and North Dakota State University found that when subjects were faced with some difficult tasks or stressful situations, if they were asked to grasp a small ball, they could make them feel more positive, optimistic, and confident, and their performance would be better. The two groups of volunteers performed the same shorthand and oral arithmetic tasks, and the comprehensive scores of the volunteers who were provided with grasping the elastic ball increased by about 26% compared with the other group. So, when we insert our fingers into the rice, we are actually doing a grasping action, but we use rice grains instead of balls or other objects. This grasping action can make our brain more active, and give people a sense of control and confidence, a sense of stability in the heart, and thus a sense of pleasure.

Why is rice more delicious?

Why do we have such a liking for rice, but always find other grains such as soybeans, mung beans, oats, etc. unsatisfactory?

Source: pexels

First of all, it may be because of the size and shape of rice grains. Rice grains are generally rectangular, about 5-8 mm long, and of moderate size, which allows our fingers to feel tightly wrapped when inserted, but without causing a sense of oppression that causes pain and discomfort. Other grains, such as soybeans and mung beans, are generally round in shape and larger in size than rice grains, making it difficult for them to fit tightly against the fingers. There will be larger gaps, and they cannot achieve the tighter wrapping feeling of rice, which will make our fingers feel less full or less smooth when inserted; and oatmeal grains are generally flat and rough, which may make our fingers feel less smooth when inserted.

Source: The Paper

Secondly, the friction and gaps between rice grains are also important. There is a certain amount of friction between rice grains, which can make the oval rice grains change regularly under the movement and squeezing of our fingers: the vertical rice will be squeezed downward, forcing the surrounding rice grains to move horizontally, and the rice grains moving horizontally will further push the surrounding rice grains to spread. After being compressed to a certain extent, the rice grains will be forced to roll upward, thus giving our fingers a rhythmic stimulation. There are also certain gaps between rice grains, which can make the rice grains produce sound feedback when our fingers are inserted and pulled out, and also bring us psychological pleasure.

In summary, we can see that the feeling of inserting your fingers into rice is a complex and magical phenomenon, which involves our skin, nerves, blood, temperature, psychology and other aspects, and also reflects our personal preferences, living habits and other factors. However, we still do not recommend that you insert your fingers into the bulk rice in the supermarket, which not only affects other people's shopping experience, but also wastes food in the process of inserting your fingers into the rice.