Do babies dream? The answer, quite simply is, yes - as far as we can tell.
Dr Charles P Pollak, director of the Center for Sleep Medicine in New York, points out that newborn infants all display REM sleep, because you can literally see the rapid eye movements under their eyelids.
He explains that this REM behavior is "an evolutionarily old type of sleep that occurs at all life stages, including infancy, and even before infancy, in fetal life."
So it is a well-based inference that babies are dreaming during this REM sleep.
As for the content of babies' dreams, Dr Pollak said: "That is like asking whether your pet dog or cat is dreaming, because they can't communicate, and you can't ask. We presume that infants dream infantile things, but we don't really know what it is that they dream."
If you've ever watched your pet dog sleep, you can sometimes see their feet twitch as if they're dreaming of running. Or sometimes they make little baby barks in their dreams - subdued versions of real life actions. So if your dog dreams about the the thing he loves doing most... what do babies dream about?
"There is some evidence in adults that the direction of eye movement corresponds in a crude way to the content of the dream," Dr Pollak says. "If they are dreaming about walking in a field," he said, "the movement is most likely horizontal. If they dream of looking up at a building or climbing stairs, vertical eye movement is more likely to predominate. We can't go further than that."
Sure, the scientists can't go further than that. But we can have fun guessing. My guess as to what they dream about? Babies dream of lying around pooping their pants, watching the world go by, and searching for giant nipples to suck on...