What is herd immunity?
Herd immunity occurs in populations when individuals who are not immune to a disease are protected because enough people in the population are immune to that disease. In today’s society, the most common form of creating an immunity against a disease is through vaccination. Herd immunity occurs when enough people in a society are vaccinated against a disease, and the disease is essentially unable to spread. The people who are unable to get the vaccine, often for serious medical reasons, will benefit from everyone else receiving the vaccine. They are “herd immune.” When immunization or vaccination rates fall below a certain threshold, these individuals no longer experience herd immunity and are vulnerable to the disease. Imagine, for example, that 100 people are standing in an area where it is raining. If 90 people use umbrellas, there is a pretty good chance the last ten not using umbrellas will experience herd immunity and stay dry. However, if only 50 people use umbrellas, the chance of the other 50 people getting wet increases.
Why do I cry when I laugh?
You’re supposed to laugh when you’re happy and cry when you’re sad, right? Cry-laughing is in that strange in between moment when you laugh so hard that you start crying. There are a few explanations for this weird phenomenon. Some scientists think that because crying and laughing are both responses to high emotional arousal (like being happy or sad), our bodies don’t always distinguish between the particular emotions we’re feeling. As a result, sometimes our bodies can make us cry and laugh at the same time, because all it recognizes is that you’re feeling emotionally aroused, regardless of whether that emotion is sad or happy. Another explanation is that the same parts of our brain control crying and laughing. In addition, some scientists theorize that when you laugh, you put pressure on your tear ducts, which causes the tears to come out as a reflexive response.