Consciousness, behavior, and clinical impact of the definition of pain

When we exposed the inapplicability of the current definition of pain to neonatal experiences [8], objections to our viewpoint hinged on the absence of consciousness in such nonlinguistic beings [37]. The evidence reviewed in this focus article demonstrates the occurrence and manifestations of consciousness during evolution and human development. Consciousness is described in the full-term newborn, the premature neonate, and the developing human fetus. The clinical implications of ignoring its existence excludes these patients from the benefit of pain relief, promotes more lenient criteria for their participation as research subjects, and produces marked changes in professional attitudes and analgesic practices. We conclude that the definition of pain imposes more stringent standards for acknowledging the presence of pain in nonlinguistic beings and should be changed to include sources of evidence other than verbal self-report.