SciShow host Hank Green offers an interesting explanation of the fascinating intelligence and cognitive abilities that octopuses possess and how their unique physiology helped get them there.
So, anatomically, octopuses are some pretty cool invertebrates. But what about their behavior? Octopuses have been observed using tools — like picking up two coconut halves to use as a mobile home — and manipulating objects in a way that looks a lot like playing. One 1993 study published in the Journal of Comparative Psychology even suggested that octopuses seem to display distinct personalities — reacting to food and threats in individual, but consistent ways. One octopus might be consistently curious and daring, while another is careful and shy. Another study, in 2001, seemed to show that young octopuses changed their behavior over the course of weeks, becoming more alert to danger and learning from their environment. So octopuses do seem to have some sort of advanced cognition — learning and changing their behaviors over time. …Octopuses might not look like us, move like us, live like us, or probably even think like us. But they have somehow evolved intelligence in ways we’re only beginning to understand.