How real is virtual reality? Psychologist Martin Crawshaw at Hull university aims to find out with help from a robot developed by his colleagues in the electronic engineering department.

The device, called reactobot, has been developed to test whether virtual reality-based training systems designed to simulate working environments actually feel "real" to their users.

The brainchild of robotics expert Paul Taylor of the university's electronic engineering department, the reactobot can be programmed to respond in different ways, producing a "feel" for the user that aims to correspond closely to the actual response of a particular tool when it is used in reality. This could be an aircraft joystick, a soldering iron or a scalpel. Reactobot could for example be programmed to create the feel of tissue yielding or the resistance of bone during surgery.

Dr Crawshaw says: "The characteristics of the virtual tool can be altered according to whatever instructions are given to the computer, so that it can seem heavy, viscous or elastic -- whatever properties are required to make it feel the same as the tool people are training to use."

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Dr Crawshaw says that his work will involve carrying out visual psychophysics experiments on reactobot users. "We'd like to find out about the sensitivity of people to different physical properties. How fine a description of elasticity, for example, do they really need in a virtual environment before it is accepted as "real". Similarity between the appearance of the real tool and the visual image will also be investigated.

He says that there is a lot of evidence to show that where there is discrepancy between what the visual system is telling a person and the information being provided by other senses such as touch, it is vision that is generally believed: "If it looks right, it will feel right."

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By determining reactobot's discrepancies in producing feel across a whole range of virtual reality-based training applications, it will be possible for researchers to make calculations for how much more sophisticated the engineering for reactobot needs to be.