Dreams and dreaming: Stone Age defence mechanisms or by-products of sleep?

Abstract

This article focuses on Antti Revonsuo’s threat simulation theory of dreams (TST). The theory states that dreams are biological defence mechanisms that were selected because they helped our Stone Age ancestors practise, in virtual reality, how to detect and avoid threats encountered in the environment of evolutionary adaptedness (EEA), thus contributing to survival and improved reproductive success. This article examines the available empirical evidence for TST, and finds it weak and inconclusive. It also highlights some underlying conceptual and methodological issues concerning dream research. The article concludes that given the paucity of empirical evidence supporting TST and considering the bizarre nature of dreams, dreams are best understood as by-products of sleep with no biological function.