Some further indication that the mental processes of ancient peoples differed from ours may be found in an analysis of the earliest reported dreams. At least this is the gist of an argument made by Julian Jaynes in a lecture called "The Dream of Agamemnon," published in The Julian Jaynes Collection.
Jaynes surveys the early (and admittedly scanty) literary accounts of dreams, focusing on the ancient Greeks, Mesopotamians, and Hebrews. He finds that nearly all of these dreams can be categorized as "bicameral," in line with his theory of the bicameral mind.
What is a bicameral dream? First let's look at a modern, subjective dream. Typically we see ourselves engaged in some activity far removed from bedtime. We might be walking on a beach or playing the piano at Carnegie Hall. Jaynes says we dream this way because we have developed a reflective consciousness that can generate an interior mind-space and then move an analog 'I' through this space.
His bicameral men, on the other hand, had no such subjective consciousness, and therefore could not have had such dreams. And, he finds, they did not. Instead, their dreams took the form of Agamemnon's dream, as reported in the Iliad. (This is not to say that the historical Agamemnon actually had such a dream, only that the story presents a dream in a form that would have been familiar to its audience.)
In his dream, Agamemnon is asleep in his bed (just as he is in reality). A messenger from the gods comes to him, stands over his bed, and says,
Do you sleep, now, son of warlike Atreus, the horse-tamer? A man of counsel, charged with an army, on whom responsibility so rests, should not sleep! Listen closely now, I come as Zeus’ messenger, who cares for you, far off though he may be, and feels compassion. He would have you arm your long-haired Greeks speedily, for the broad-paved city of Troy lies open to you. The immortals that dwell on high Olympus are no longer at odds, since Hera has swayed all minds with her pleas, and the will of Zeus dooms the Trojans to sorrow. Hold fast to this, remember all, when honey-tongued sleep frees you.
Agamemnon is the passive recipient of divine instructions, and even in his dream he never leaves his bed.
Jaynes also mentions the famous dream of "Jacob's ladder" (or "stairway" -- possibly a tiered tower, i.e., a ziggurat). Traveling alone, the Biblical patriarch Jacob falls asleep outdoors while using a stone as a pillow.
And he dreamed, and behold, there was a ladder set up on the earth, and the top of it reached to heaven; and behold, the angels of God were ascending and descending on it! And behold, the Lord stood above it [or "beside him"] and said, "I am the Lord, the God of Abraham your father and the God of Isaac; the land on which you lie I will give to you and to your descendants ..."
As Jaynes notes, "Jacob does nothing at all. He does not say anything – he is still asleep." But upon waking, he anoints the stone with oil and names the location Bethel (house or gate of God), apparently because he believes that the mystical ziggurat actually appeared on that very spot. ("And he was afraid, and said, 'This is none other than the house of God, and this is the gate of heaven.'")
As Jaynes says, Jacob's kind of dreaming is quite different from ours: "When Jacob wakes up, he is sure it happened right there where he was sleeping. When you wake up, you do not think the dream happened right there in your bed and look under the covers."
These and other early dreams, though they don't constitute proof, are at least consistent with the idea that ancient people did not narratize their experience in terms of an analog 'I' moving through a mental space, and that, lacking reflective consciousness, they heard voices and saw visions that told them what to do.