Sometimes, you just can't help it. Maybe you're watching a sad movie, or thinking about the friend who moved away. Why do people cry? What are tears (眼泪)？ Scientists are working hard to find the answers to these questions.
Ad Vingerhoets is a professor of psychology (心埋学) at Tilburg University, in the Netherlands. He is one of the few scientists in the world who has studied crying. According to Vingerboets, there are three kinds of tears. Basal tears are the first type. They act as a protective object between the eye and the rest of the world. Next are reflex tears. They wash your eyes clean when something gets in them. Finally, there are emotional tears. "They are connected with our feelings," explains Vingerboets. "Especially when we feel helpless. "
Scientists believe that crying has something to do with how humans developed and learned to depend on each other. "Humans are very complex (复杂的)，" says Lauren Bylsma, a professor from the USA. "It seems that tears serve to get help and support from others. " She says another reason we cry is that humans have the longest developmental period (时期) of almost any animal. It takes a long time for humans to grow up.
Vingerhoets _____________. "I think that the reason why humans cry has to do with our long childhood. " he says. "That's the time when we are still dependent on adults for love and protection and care. Tons ware a safer way to be noticed by others. In this case, it is better to use a silent signal to ask for help," he says.
Vingerhoets and Rylsma do lots of studies to better understand why humans cry. According to Bylsma, there is still much more to discover. "It's surprising." she says, "how much we still don't know."
