We tend to associate virtual reality more with recreational activities, such as video games, than with serious science, yet, increasingly, we are finding useful applications for this technology in neuroscience research and psychotherapy. Computer simulations can potentially recreate a limitless range of 'real-life' situations in the research laboratory, and virtual environments are being used successfully to enable people with phobias to face and conquer their fears. As Sanchez-Vives and Slater discuss in an Opinion article on page 332 of this issue, the success of a virtual environment depends on its ability to evoke presence — the sense that an individual is present in a virtual world rather than the place where their body is actually located. Presence can be measured in terms of emotional and behavioural reactions to a virtual environment, as well as by physiological responses, such as sweating or increased heart rate.

Sanchez-Vives and Slater argue that virtual reality has the potential to be more than a passive research tool, and that presence research could provide valuable insights into perception and consciousness. One unexpected result that has emerged from presence research is that presence can be induced at a surprisingly low level of visual realism. This observation might be exploited to determine the minimal features that a virtual environment requires for it to be perceived as real, and to study the extent to which cortical processing can 'fill in' the missing elements of a scene. It would also be interesting to discover what happens in the brain at the point where consciousness is transported from the real world to a virtual world. So far, presence research has been conspicuous by its absence from the neuroscience literature, but this Opinion article should go some way towards rectifying this situation.