Simplify the following text for a Grade 8 native English-speaking person.
Original: It is also widely believed that the size and number of connections in the prefrontal cortex relates directly to sentience , as the prefrontal cortex in humans occupies a far larger percentage of the brain than any other animal . And it is theorized that as the brain has tripled in size over 5 million years of human evolution , the prefrontal cortex has increased in size sixfold .
Simplified: The prefrontal cortex is a part of the brain that helps to control behavior .