The exploration of consciousness in insects.

Consciousness is a state of subjective experience or awareness, e.g. of an emotion, the self or external objects. In humans, this awareness is underpinned by a suite of cognitive functions, from attention to metacognition. To understand the evolution of consciousness, the study of these cognitive functions across a variety of animal taxa is critical. Insects are useful organisms because we have a sophisticated understanding of their cognition from over a century of study and modern tools are revealing the intricacies of insect brains with increasing clarity. Here we cover the rich history of this venerable field as well as more recent discoveries relating to consciousness in insects, specifically focusing on the following areas: emotions, the distinction of self and other, prediction, attention and active sleep. There can still be no formal certainty about consciousness in insects; even in humans, there is currently no agreement over the particular combination of cognition and neural function that produces consciousness. Nonetheless, evidence from all the lines of investigation summarized here builds up to an increasing probability that insects might possess some form of subjective experience. We encourage further investigation of insects to explore the building blocks of consciousness and its evolutionary antecedents.This article is part of the theme issue 'Evolutionary functions of consciousness'.