THAT a complex mind is required for religion may explain why faith is unique to humans. Now brain scans support this idea, revealing that the parts of the brain that process religious belief are those that evolved most recently and give us sophisticated cognition.

These regions include ones involved in our theory of mind. We share this ability to recognise that other people have intentions and thoughts independent of our own with only a few other species, including chimpanzees. Other regions involved in religious thought are ones used for language and metaphor.

Jordan Grafman of the US National Institute of Neurological Disorders and Stroke in Bethesda, Maryland, and colleagues asked 40 monotheistic believers whether they agreed with statements relating to three core elements of belief: whether God intervenes in the world; how to interpret God's emotional state; and how to relate to abstract doctrinal teachings or imagery. The researchers scanned the believers' brains as they answered.

While considering the first two statements, volunteers relied on areas such as the lateral frontal lobe and frontal gyri, which are required for a theory of mind. For the doctrinal statements, they used areas devoted to linguistics, decoding metaphor and recalling images (Proceedings of the National Academy of Sciences, DOI: 10.1073/pnas.0811717106). "We were particularly interested in determining which cognitive components of belief are stored in brain areas most evolved in humans," says Grafman.

Anthropologist Robin Dunbar of the University of Oxford says the results back his own theory that brain areas enabling the "higher orders of intentionality" shown by humans had to evolve before religion was possible. He suggests that religious people treat gods as "having essentially human mental traits, like characters in a novel or play".

Grafman stresses that the scans don't shed light on whether or not God exists. "They only address how the mind and brain work in tandem to allow us to have belief systems that guide our everyday actions."

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