system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5 Why babies laugh at peekaboo so much

Edit: I just noticed I don't have a question mark in the title

Edit 2: I forgot the "do" after the "why"

Edit 3: Okay now that I think about it, I wrote the title like ELI5 was part of the sentence. "Explain like I'm five why babies laugh at peekaboo so much."
gpt
Object Permanence, or the ability to recognize that an object still exists even if it changes form (like the same amount of water just switched containers) or that it becomes hidden.  It is fascinating for them to see someone appear and disappear almost instantly.