Adopting an approach based in cognitive archaeology, Lewis-Williams and Pearce argued that the chambered long barrows "reflected and at the same time constituted... a culturally specific expression of the neurologically generated tiered cosmos", a cosmos mediated by a system of symbols.[46] They suggested that the entrances to the chambers were viewed as transitional zones where sacrificial rituals took place, and that they were possibly spaces for the transformation of the dead using fire.[40]