We study visual behaviour in diverse organisms including insects, birds, primates and cephalopod molluscs, to address a range of questions about colour and spatial vision. The aim is to understand how eyes have evolved and how animals use vision to recognise the objects, to communicate and to camouflage themselves.

With Misha Vorobyev I developed a model of colour vision to predict the discriminability of light spectra from photoreceptor spectral sensitivities. This can be applied to any animal where receptor sensitivities are known and we have an estimate of noise in the receptor signals. These models account well for psychophysical measurements of spectral sensitivity in a wide range of animals and are widely used.
 
To understand the evolution of primate colour vision – including human -  I have collaborated with Peter Lucas, Hannah Buchanan-Smith, Nick Mundy and others to compare primate trichromacy to other types of colour vision for tasks such as finding colourful fruit or cryptic insects.
 
I study bird colour vision, by testing young poultry chicks in naturalistic foraging task, where they make much use of colour, but with printed paper stimuli that nonetheless give well-defined photoreceptor excitations. This has found strong evidence for tetrachromatic colour vision based on the four single cones in the bird eye, and that the double cones are probably used for tasks such as pattern and motion perception, which are colour blind. With Roland Baddeley and others we have investigated higher-level phenomena, showing how chicks generalise, categorise and learn about colours and simple patterns
 
Cuttlefish (a cephalopod mollusc) produce a vast range of body patterns under visual control for camouflage and communication, which give unique and rich insight into the vision of an animal without language. By analysing the patterns produced in different experimental contexts we have shown how these remarkable animals perceive their visual environments to select camouflage patterns and to deter predators.
 
With John Anderson  I have developed a method for recording spectral and colour data reliably with ordinary cameras. This system is Patented by the University of Sussex and is being developed for use in medical photography and other applications.