Insects are conscious, egocentric beings, argue Australian scientists in a new paper that suggests basic consciousness may have first evolved in insects in the Cambrian Period.

Key points: Insects have capacity for basic consciousness known as subjective experience

Insects have capacity for basic consciousness known as subjective experience Insect brain works in a similar way to human midbrain, which is responsible for subjective experience

Insect brain works in a similar way to human midbrain, which is responsible for subjective experience Cambrian insects would have needed core brain systems to support foraging and hunting argue researchers

Recent neuroimaging suggests insects are fully hardwired for both consciousness and egocentric behaviour, providing strong evidence that organisms from flies to fleas exhibit both.

Consciousness comes in many levels, and insects have the capacity for at least one basic form: subjective experience, the researchers argue in paper published today in the Proceedings of the National Academy of Sciences.

"When you and I are hungry, we don't just move towards food; our hunger also has a particular feeling associated with it," said the paper's co-author Dr Colin Klein a philosopher at Macquarie University.

"An organism has subjective experience if its mental states feel like something when they happen."

Dr Klein and his colleague biological scientist Associate Professor Andrew Barron, also of Macquarie University, studied detailed neuroimaging reports concerning insect brains.

They then compared the structure of such brains with those of humans and other animals.

Their work focused on the midbrain, a set of evolutionarily ancient structures that are surrounded by the grey folds of the cortex. The arrangement, they said, looks a bit like the flesh of a peach surrounding the pit.

"In humans and other vertebrates (animals with a backbone and/or spinal column) there is good evidence that the midbrain is responsible for the basic capacity for subjective experience," said Dr Klein.

"The cortex determines much about what we are aware of, but the midbrain is what makes us capable of being aware in the first place. It does so, very crudely, by forming a single integrated picture of the world from a single point of view."

Weaver ants (Oecophylla smaragdina) are known for their cooperative behaviour used in nest construction. ( Ajay Narendra )

Portions of insect brains work in a similar way to the midbrain in humans, performing the same sort of modelling of the world, said the authors.

As for being egocentric, there is now compelling evidence that insects display selective attention to their processing of the world, said Dr Barron.

"They don't pay attention to all sensory input equally," he explained. "The insect selectively pays attention to what is most relevant to it at the moment, hence [it is] egocentric."

The term "insect" is a broad one, generally referring to any small animal that has six legs, a body formed of three parts, and may have wings. Since diverse species under this umbrella term have widely varying sensory systems and ways of life, the authors expect that to be reflected in their conscious lives.

Not all living things are thought to have consciousness, though. Plants, for example, do not have the necessary structures for it. Jellyfish and nematodes (certain unsegmented worms, such as roundworms) do not have such hardwiring either.

Origins of consciousness traced back to Cambrian

Dr Barron and Dr Klein believe the origins of consciousness date to at least the Cambrian, which began around 540 million years ago.

"When organisms began to move freely in their environment, they faced many new challenges," Dr Klein explained.

"They had to decide where to go next. They had to prioritise their needs. They had to interpret sensory information that changed as a consequence of their motion. That required a new kind of integrated modelling, and that's where we think consciousness arose."

Bruno van Swinderen is an associate professor at the University of Queensland and is a leader in the field of insect neurobiology.

Dr Van Swinderen believes one of the most important points of the new paper is the realisation that understanding the evolution of consciousness will not come from looking for intelligent behaviour in other animals, but rather from understanding the fundamental mechanisms that support subjective awareness and selective attention, which he said "we now know insects have."

"Insects have traditionally been viewed as mini robots, responding to environmental stimuli in a rather inflexible way," said Dr Van Swinderen.

"In contrast, Barron and Klein suggest that it is likely that some of the fundamental underpinnings of consciousness have already been solved in even the smallest brains."

Completely understanding what's on the mind of an insect is still impossible, however.

As Dr Klein said: "In some sense it's very hard to understand what other people experience, much less animals! But we think that research can reveal much about the contents of insects' experience, as well as the similarities and differences in the way that these experiences are structured."

This article was first published on DiscoveryNews.com.