Why do we have eyebrows? Wait. Let me ask Lord Voldemort. Haha. Eyebrows actually serve many functions. Firstly, eyebrows protect our eyes. Without them, the sweat and rain would easily enter our eyes and hinder our vision. Also, the salt in our sweat would irritate our eyes. But the arched shape and direction of hair help channel sweat. And rain towards the sides of our faces, thus protecting our eyes. Secondly, eyebrows help to express emotions. In a study. It was found that our ancestors were not able to easily move their eyebrows. But due to evolution. We gradually gained the ability to move them to a greater extent. Thus helping us express a wide range of emotions like surprise, anger, etc. Lastly, eyebrows also help in recognizing faces. In a study. Scientists found that participants had a tougher time recognizing famous people’s faces. When their eyebrows were erased than when their eyes were erased. Why do we feel butterflies in our stomach? Because I have invited them to my party. Naahhh. Butterflies in our stomach are basically caused by our autonomic nervous system or ANS. ANS regulates our involuntary functions like heartbeat, blood flow, digestion, etc. Also, during stressful situations such as when a ferocious animal comes in front of us. A part of ANS called the sympathetic nervous system prepares our body for fight or flight. This means, it redirects blood from other parts of the body to mostly our hands and legs. So that they get sufficient oxygen and nutrients and thus, help us fight or flight. So then why do we feel butterflies in our stomach? It is believed that since blood is redirected from the stomach. Millions of sensory nerves in it detect a sudden decrease in oxygen. Hence, in response to this, the nerve cells create the feeling of butterflies. Also, because of blood redirection, it is thought that the stomach contracts. Thus contributing to the feeling of butterflies. Why does it feel so good to scratch an itch? Because scratching gives us new ideas. Oh no. When there is an allergic reaction or when insects like mosquito bite. The itch receptors of that region send itch signals to the brain. Now, as a protective response, we scratch the itch. In order to remove or dislodge the insect. Or whatever is on the skin that is causing the itch. In addition to this, scratching also helps reduce the itch sensation. But how? Scratching activates pain receptors. So, the idea is that when we scratch. The neurons in the spinal cord transfer pain signals instead of itch signals to the brain. When the pain signals reach the brain, it releases a neurotransmitter called serotonin. Which is a happiness related chemical to make us feel good and thus, dull the pain. In this way, scratching an itch makes us feel good. Why do we bite our nails? To save our expenses on manicure. No. Nail biting or onychophagia is a bad habit. And there is no specific reason why people do it. I will find the reason in only 2 seconds. Don’t bother. A habit forms due to three things, a trigger, action and reward. So, in case of nail biting. A research suggests that a broken nail which is hurting can be a trigger. Biting and removing it is the action. When the broken nail is taken off, the pain is reduced and we feel better. This is our reward. Now, if we again encounter similar triggers like a broken nail. We repeat the same action to get the reward.