In the next video, we will watch an older child, a 3-year-old, learn an even more complex causal relation just by watching. The experimenter will play with two different toys, a green block and a yellow block. When she puts both toys on a box, it will make a marble dispense from the marble machine. Then, when she puts the green block on the box by itself, nothing will happen. No marble will come out. Then she asks the child which toy makes the marble machine go. The child has only seen the green block on the box by itself, so he doesn’t know what the yellow block will do on its own. As an adult, we can reason about what we’ve seen. The green block doesn’t make the machine go on its own. But the green block and the yellow block on the box together make the machine go. Therefore, the yellow block is probably what makes the machine go. We can reason in this way even if we never see the yellow block on the box on its own. Let’s see what the child does.