The model
Lewis-Williams and Dowson proposed that geometric motifs in rock art correspond to entoptic form constants produced by the visual system in altered states, and read the art as evidence of shamanic practice.
The critique
Critics point to circular reasoning, the universality of simple geometric forms, ethnographic overreach onto Upper Palaeolithic Europe, and the absence of independent tests. The San ethnography that anchored the model does not automatically transfer to Chauvet or Lascaux.
Where this leaves prehistory
Prehistoric ritual specialists are plausible and in some cases well-evidenced by burials such as Hilazon Tachtit and Bad Dürrenberg. Reading whole cave-art traditions as shamanism remains an interpretation, not a finding.