Do animals dream?

Dreaming is hard to study in non-human animals because it is usually identified through verbal reports. Parallels between human dreaming—its phenomenology, physiology, and behaviors—offer a way forward. Three alternative measures of human dreaming (neural correlates, memory replay, and dream-enacting behaviors) can be applied to animals. Mammals and birds, with brains similar to humans, are good models for neural and memory measures. Cephalopods, especially octopuses, may be especially suitable for studying dream-enacting behaviors.

Study at a glance

Abstract

The understanding of biological functions of sleep has improved recently, including an understanding of the deep evolutionary roots of sleep among animals. However, dreaming as an element of sleep may be particularly difficult to address in non-human animals because in humans dreaming involves a non-wakeful form of awareness typically identified through verbal report. Here, we argue that parallels that exist between the phenomenology, physiology, and sleep behaviors during human dreaming provide an avenue to investigate dreaming in non-human animals. We review three alternative measurements of human dreaming - neural correlates of dreaming, 'replay' of newly-acquired memories, and dream-enacting behaviors - and consider how these may be applied to non-human animal models. We suggest that while animals close in brain structure to humans (such as mammals and birds) may be optimal models for the first two of these measurements, cephalopods, especially octopuses, may be particularly good candidates for the third.