Octopuses have a favorite arm for each task

"They documented over 4,000 arm movements, which allowed them to create what they call an ethogram a catalog of the species' behaviors or actions. They identified 15 behaviors (ranging from hiding to mating) and 12 movements (from lifting to reaching) of their eight arms, each of which can perform four basic deformations: elongating, contracting, stretching, or twisting. Adding to this complexity, each deformation can occur in the part of the arm closest to the head (proximal), the middle, or the tip (distal)."

"One key finding is that each of the eight arms is capable of performing all types of actions; however, they also detected a clear pattern of task distribution. For example, the front limbs are mainly used for movements that help explore the environment, while the rear limbs are used for actions related to locomotion. A specific detail points to the proactive nature of this unusual animal: the two front arms are used 64% of the time, while the two rear arms are used only 36% of the time."

Researchers recorded 25 octopuses from three species across six ecosystems, including three individuals in the Vigo estuary. They documented over 4,000 arm movements and created an ethogram cataloging 15 behaviors and 12 arm movements. Each arm can perform four deformations—elongating, contracting, stretching, twisting—at proximal, middle, or distal segments. All eight arms are capable of every action, yet task distribution shows specialization: front limbs predominantly explore the environment while rear limbs mainly support locomotion. The two front arms are used 64% of the time versus 36% for the rear pair. Octopuses rely more on tactile sensing than vision and show no consistent lateralization.

Read at english.elpais.com