That's right. Children transfer their emotions into their drawings and yes, you're right, psychologists use this as a means to assess the emotional and mental state of the children. I can remember when I used to draw as a child, I would always draw 5 kids (which is me and my siblings) and my dad. My mother was always away.

Thank you @scarletmedia for your comment. It is also a good reminder for me to be more attentive and observant of my students' art work, such as painting and drawing, and their writing, too.