William McDougall was a man who lived a long time ago and was very interested in how people think and behave. He was a kind of detective who wanted to figure out why people acted the way they did.
One of his ideas was that our behavior is influenced by something called instincts. You know how sometimes when you're hungry or thirsty, your body tells you, "Hey, I need some food or water?" well, that's kind of like an instinct. It's a feeling we get that makes us do something without even really thinking about it.
McDougall also thought that our emotions like fear and love were also connected to these instincts. So, if you're feeling afraid, it could be because your instincts are telling you something isn't safe.
One other thing McDougall was really interested in was how we learn new things. He thought we could learn through trial and error - like if you try to build a Lego tower and it falls over, you learn how to make it stronger next time - or by watching other people and copying them.
Overall, McDougall was one of the first people to study human behavior in a scientific way, and his ideas helped us understand more about why we do the things we do.