What is Nest-building in primates?

Nest-building in primates refers to the behaviour of building nests by extant strepsirrhines and hominid apes. Strepsirrhines build nests for both sleeping and raising families. Hominid apes build nests for sleeping at night, and in some species, for sleeping during the day. Nest-building by hominid apes is learned by infants watching the mother and others in the group, and is considered tool use rather than animal architecture. Old World monkeys and New World monkeys do not nest.It has been speculated that a major evolutionary advance in the cognitive abilities of hominoids may first have occurred due to the development of nest-building behaviour and that the transition from nest-building to ground-sleeping led to "modifications in the quality and quantity of hominid sleep, which in turn may have enhanced waking survival skills through priming, promoted creativity and innovation, and aided the consolidation of procedural memories".