In paragraph 3, depressed faces were those people who came out acting very different towards others. When I observed those other 15 people from group A, they did not all come out crying. Crying is a way to express depression and a somewhat miserable behavior. But among these 15 college students, they were simply quiet. They were very calm and did not show any signs of depression, such as crying or weeping. These 15 students did not show much impact but they did come out with a totally different behavioral change. A for sure fact was that within all 20 students from group A, they did not show any signs of smiling happily or talk regularly.
In paragraph 4, being joyful and happy means the total opposite of depression. This behavior can be expressed by smiles on people's faces, talking more often than usual, and smiling naturally without any kind of force.
Those students who were friendly came out much more talkative which means to deliver or express in speech and to make the subject of conversation or discourse.
Those students also showed a lot of motivation which means something (as a need or desire) that causes a person to act and a recurrent phrase or figure that is developed through the course of a musical composition. These students' performance had a lot of energy. They seemed perfectly normal compared to those students from group A.