A haptic computer output device comprises a data glove 10 the finger and thumb extension 10A and 10B of which have spaced ring formations 13 and 14. Each ring formation 13 and 13 is formed with an inwardly-opening blind bore 21 spanned in gas-tight manner by a membrane 23 and conduits 20 within the ring formations selectively apply pressurised air to or relieve it from the bores 21 under the control of a valve assembly 34 in turn controlled by a computer 30. The computer generates images perceived on a visual system 32 by a wearer of the glove. Data concerning the spatial position and flexing of the glove 10 is transmitted via line 31 to the computer, which additionally generates a cursor on the visual system 32. When this interacts with other virtual objects to simulate a "touch" the appropriate bore 21 is inflated via valve assembly 34 to apply a tactile stimulus to the wearer of the glove.