What is the main idea of the lecture?

Questions 1 through 5. Listen to part of a lecture in a biology class.
A growing body of research shows that the two halves of the brain specialize in different behaviors. The left brain controls behaviors involving approach and energy enrichment, while the right brain controls behaviors involving withdrawal and energy expenditure. In humans, the left brain is associated with positive emotions, such as love, and with feelings of safety and calm. The right brain, in contrast, is associated with withdrawal behaviors, such as fleeing, and with negative emotions like fear and depression.
It’s important to remember that each side of the brain controls the opposite side of the body. The left brain controls the right side of the body, while the right brain controls the left side of the body. This means that emotions associated with one side of the brain are expressed in the opposite side of the body. For example, the muscles on the right side of our face tend to reflect happiness—a positive emotion controlled by the left brain— whereas the muscles on the left side of our face reflect unhappiness, which is a right-brain emotion.
Now, some researchers have argued that only humans show left and right biases in the brain. However, these same biases are showing up in the brains of animals. When chimpanzees are upset, they tend to scratch themselves on the left side of their bodies, reflecting the right brain’s control of strong negative emotions. Birds show the same brain asymmetry. Because their left brain controls nourishment, a lot of birds look for food with their right eye. Similarly, because their right brain controls danger, they watch for predators with their left eye.
A recent study of body language in dogs supports these same left-right biases. The muscles in the right side of the dog’s tail reflect positive emotions, while the muscles in the left side express negative ones. When dogs feel positive about something— for example, when they see their owner—they wag their tails more to the right side of their rumps. On the other hand, when dogs see an unfamiliar, aggressive dog, their tails wag more to the left.
The research suggests that an animal’s body is hard-wired so that major nerves send certain kinds of information to the preferred side of the brain. Information that prompts an animal to eat, relax, or restore itself is biased toward the left brain. Conversely, information that tells an animal to run, fight, or watch out for danger is biased toward the right brain.
1. What is the main idea of the lecture?
2. What point does the professor make about the two sides of the brain?
3. Why does the professor say this:
"When chimpanzees are upset, they tend to scratch themselves on the left side of their bodies, reflecting the right brain’s control of strong negative emotions."
4. What does the professor imply by this statement: "On the other hand, when dogs see an unfamiliar, aggressive dog, their tails wag more to the left."
5. Indicate whether each behavior is associated with the left brain or the right brain.