Joshua Sokol for Quanta Magazine:
And then there are animals that appear to offload part of their mental apparatus to structures outside of the neural system entirely. Female crickets, for example, orient themselves toward the calls of the loudest males. They pick up the sound using ears on each of the knees of their two front legs. These ears are connected to one another through a tracheal tube. Sound waves come in to both ears and then pass through the tube before interfering with one another in each ear. The system is set up so that the ear closest to the source of the sound will vibrate most strongly.
In crickets, the information processing — the job of finding and identifying the direction that the loudest sound is coming from — appears to take place in the physical structures of the ears and tracheal tube, not inside the brain. Once these structures have finished processing the information, it gets passed to the neural system, which tells the legs to turn the cricket in the right direction.The Thoughts of a Spiderweb
The broader concept is known as “extended cognition,” and in my view it may just be semantics. Many natural and artificial features of our environments, from ear shape to computers, amplify and filter information in ways that reduce cognitive load. I’d hesitate to describe these as “cognition.” But intelligence as a concept is certainly broader than brains.