Odin keeps two ravens, Huginn and Muninn, whose names mean roughly thought and memory. They fly out over the world each day and return to tell him what they have seen, and Snorri's Prose Edda records Odin saying he fears more for Muninn's return than Huginn's, a line usually read as anxiety about memory rather than intellect. Odin's raven association is part of a wider battlefield connection: ravens follow armies because armies produce carrion, and Old Norse and Old English poetry has a recurring formula, the beasts of battle, in which raven, eagle and wolf attend a slaughter. This is realism before it is symbolism.
The Bible uses the raven twice in quick contrast. Genesis 8:7 has Noah send out a raven, which goes to and fro without returning, before the dove; 1 Kings 17:4-6 has ravens bring bread and meat to Elijah at the brook Cherith. Leviticus lists the raven among unclean birds, which makes the Elijah passage more pointed rather than less.
The cognitive research is genuinely striking and is worth stating carefully. Corvids cache food and will re-cache it if another bird watched them, which requires tracking what a competitor has seen. New Caledonian crows manufacture hooked tools from twigs and pandanus leaves and use them in sequence. Ravens have solved multi-step problems in the laboratory and have been shown to plan for future use of a tool. Some corvids have passed mirror-mark tests, though those results are debated.
What the research does not support is the claim, common in popular writing, that ravens can talk in any linguistic sense. They mimic sounds, including speech, as several unrelated bird families do.