After decades of research and spec­u­la­tion, the rea­sons for dream­ing are still unknown. There are many the­o­ries, of course, as Har­vard psy­chol­o­gist Deirdre Bar­rett notes as she reviews the most preva­lent evo­lu­tion­ary the­o­ries for why we dream:

  • Brain Con­di­tion­ing
  • Exter­nal Vigilance
  • Threat Sim­u­la­tion
  • Costly [Genetic] Signalling
  • Problem-Solving

The arti­cle also notes how many “notable fig­ures from all walks of life (includ­ing sci­en­tists) [have] arrived at their ground­break­ing dis­cov­er­ies and insights through dreams”. To Bar­rett, this sug­gests that “a sim­ple brain con­di­tion­ing expla­na­tion for the exis­tence of dream­ing is shortsighted”.