A Brain With 8 Arms

Q: Does an octopus have a brain? Where is it? And just how smart is an octopus?

A: In a sense, an octopus has several brains, collections of neurons that control each arm. A famous 2001 study in the journal Science described how the commands that control one arm’s movement continue even when connections to the walnut-size central processing system in the head are severed.

Since then, more has been found about why the octopus is so much smarter than the average seafood. Even the relatively small central brain of an octopus is the largest among all invertebrates — proportionally, that is. A review article in 2015 in the journal Current Opinion in Neurobiology summarized the complexity of learning processes in the octopus and its remarkable adaptability.

Some studies have examined the cephalopod’s ability to discern objects of different sizes, shapes, colors, brightnesses and textures, and its problem-solving, including the ability to navigate mazes and open jars. The creature also displays both short-term and long-term memory and recall over periods of weeks and even months.

A possible explanation of the advanced abilities of the octopus lies in its very large genome, decoded in 2015 in a study in the journal Nature.

The researchers surmised that the vast expansion of certain gene families in the octopus, and the network of linkages among the genes, could account for the development of its neurological complexity.