Children as young as 3 can figure out cause and effect relationships by observing patterns. They were shown a machine that reacted to certain objects, and they had to use clues to make guesses about how it worked. Even though some kids made mistakes, 4-year-olds were better at making accurate guesses based on the likelihood of events happening. This shows that kids don't just connect events they see, but they also learn to make smart guesses based on what they know.