In a nutshell: Bees have three extra eyes on the top of their head, which help them to see colours accurately.

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Colour constancy refers to the ability to perceive an object’s real colour, even in different lighting conditions. Remember the photo of the black and blue (or was it gold and white) dress that went viral?

For a long time, it was not clear what exactly happens in the brain to enable colour constancy. How does it discount lighting conditions to work out the true colours of objects?

Honeybees appear to solve this problem by sensing the ambient light using three extra eyes aimed at the sky. That is the conclusion of multidisciplinary research led by Jair Garcia and Adrian Dyer from RMIT University and Brain Function CoE chief investigator Marcello Rosa.

Bees have five eyes. The two main compound eyes, on each side of their head, have three colour receptors. Three smaller eyes, called ocelli, sit at the top of their head and have two colour receptors. The study found that information from all five eyes converges onto the brain areas that process colour.

Moreover, using mathematical modelling, the team found that the ocelli are perfectly suited to detect ambient light. Together, this makes a compelling case for the ocelli being responsible for discounting the illumination factor, allowing bees to find the blue flower whether it’s in full sun or under a dense canopy of trees.

“The strength of this study lies in the combination of modelling, behavioural analysis and neuroanatomy,” said Rosa. “It brought together researchers from four universities, showing how modern interdisciplinary neuroscience can point to elegant solutions to classical problems in vision.”

This research could facilitate the development of better cameras for robots and drones, as well as colour-sensitive bionic eyes.

Next steps:
The lead investigators will use this information to develop a chip for cameras that mimics the ocelli by correcting for ambient luminance to reproduce perceived colours. That would put an end to controversies about what colour a dress is in a photo!

Garcia, J. E., Hung, Y.-S., Greentree, A. D., Rosa, M. G. P., Endler, J. A., & Dyer, A. G. (2017). Improved color constancy in honey bees enabled by parallel visual projections from dorsal ocelli. Proceedings of the National Academy of Sciences USA, doi:10.1073/pnas.1703454114

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