[Octopuses can squirt water at an annoyingly bright bulb until it short-circuits. They can tell humans apart (even those who are wearing the same uniform). And, according to Peter Godfrey-Smith, a philosophy professor at University of Sydney and City University of New York, they are the closest creature to an alien here on earth.
There’s no clear way of evaluating consciousness in other animals (or in other humans, for that matter—it’s quite possible that you’re the only conscious being alive and everyone you know is merely displaying signs of consciousness rather than truly experiencing it). But we can certainly make educated guesses. Broadly speaking, consciousness is often defined as there being an experience of what it’s like to be said creature.
Octopuses display signs of curiosity, and Godfrey-Smith believes it’s extremely likely that they’re conscious beings. “I think the exploratory behaviors, the fact that they attend to things, they have good eyes, they evaluate, are little bits of good evidence that there’s something it’s like to be an octopus.”]