The field theories of consciousness do not appear to have been as widely discussed as other quantum consciousness theories, such as those of Penrose, Stapp or Bohm. However, David Chalmers argues against quantum consciousness. He instead discusses how quantum mechanics may relate to dualistic consciousness. Chalmers is skeptical that any new physics can resolve the hard problem of consciousness. He argues that quantum theories of consciousness suffer from the same weakness as more conventional theories. Just as he argues that there is no particular reason why particular macroscopic physical features in the brain should give rise to consciousness, he also thinks that there is no particular reason why a particular quantum feature, such as the EM field in the brain, should give rise to consciousness either. Despite the existence of transcranial magnetic stimulation with medical purposes, Y. H. Sohn, A. Kaelin-Lang and M. Hallett have denied it, and later Jeffrey Gray states in his book Consciousness: Creeping up on the Hard Problem, that tests looking for the influence of electromagnetic fields on brain function have been universally negative in their result. However, a number of studies have found clear neural effects from EM stimulation.