Laughter is a similar kind of release, say Marijuán and Navarro. The intellectual momentum that builds up during conversation needs to be relieved, either through verbalisation or some other mechanism. Marijuán and Navarro’s suggestion is that this other mechanism is the channelling of excess cortical excitations to parts of the brain responsible for vocalisation. But without anything specific to say, the result is the kind of panting and cackling that we call laughter. That’s why it is built in. This social significance of this behaviour is the thing that has evolved, not the activity itself.