Consciousness is a subjective, personal thing, so scientists who study it usually rely on people to tell them what they are conscious of. The problem is that infants are presumably conscious but, without speech, they can’t let us know. Animals like dogs, cats, octopuses and maybe insects might also be conscious, but they can’t tell us that either.
There are even problems with studying adult human consciousness. People might not be fully authoritative about their own consciousness. Some philosophers and scientists think that awake, attentive adults might be conscious of much more than can be put into words.
