Phenomenal interface theory: a model for basal consciousness

An increasing number of authors are willing to attribute phenomenal consciousness to relatively simple organisms like insects. Yet it is not at all clear what functional role the substrates of consciousness would play. Here, we argue phenomenal consciousness is a consequence of how mobile animals with spatial senses and a capacity for goal-directed behaviour resolve the complex problem of action selection. To adjudicate between possible goals an animal must use sensory inputs, representations of internal state and stored knowledge of values to estimate expected value vectors for different options. Brains solve this problem by taking such heterogenous information and transforming it into a common framework-a phenomenal interface-and then using this to compute multi-objective <i>Q</i>-values. We use insects to flesh out the details of the phenomenal interface. A consequence of this type of processing is that it naturally generates a distinction between self and non-self and a first-person perspective in which external stimuli have a subjective value. We discuss the consequences of this theory for understanding the evolution and distribution of phenomenal consciousness and suggest an underappreciated problem that arises when thinking about how consciousness might have expanded and changed as it evolved from its simplest origins.This article is part of the theme issue 'Evolutionary functions of consciousness'.