[legacynl]

> like how humans feel cold and put on a jumper.

This is actually a bad example. Although cold being uncomfortable is instinctual, the way how people deal with feeling cold is not instinctual at all. People use different methods of dealing with the cold depending on situation, culture, experience.

In this way your example actually speaks for the claimed forethought, because in this analogy the octopus knows (from experience or speculation) that he will be uncomfortable when trying to sleep if he's exposed and he decides to 'put on a jumper' by putting rocks in front of the entrance.

Also instinctual behavior is in general much less sophisticated. Like an infant animal starting sucking when encountering a nipple shaped object or a moth circling a light bulb because it always tries to keep the brightest source above it. It could be that pulling debris around him before sleeping could be instinctual, but it would be very unlikely for that to include the process of looking for suitable rocks beforehand.