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Movement Making You Feeling Ill? Here’s Why

by Beth Divine 4 Jun 2018

Virtual reality is known to make some people feel sick, and this has put some people off using the technology. But this type of nausea is not unknown – it was previously called simulator sickness, and was widely experienced by test pilots, stunt drivers and pilots practising their craft in simulators before getting their hands on expensive pieces of equipment and risking their lives.

Simulator sickness is very similar to motion sickness, although they are diametrically opposite problems. Motion sickness happens when you are moving, but it feels as though you are keeping still – for example in a ship or car – any form of transport – when you cannot see out of a window to ‘see’ the movement of the landscape. Virtual reality or simulator sickness happens when your brain thinks you are moving, but you are actually remaining still, such as in virtual reality games.

Movement Making You Feeling Ill? Here’s Why motion sickness1

Both of these conditions occur because of a disconnect between what the eyes are telling the brain and what the ears are telling it. Normally, when you are moving, the fluid in the semi-circular canals of the ear respond by moving also – think of how your tea or coffee sloshes around in a cup when you carry it to your desk – and your eyes, obviously, are watching where you are going, so both senses inform the brain that movement in this direction is occurring. This is how it is meant to be, so the brain is satisfied that motion is happening.

However, in a case of either simulator sickness or motion sickness, the eyes see one thing, while the ears proclaim the truth. So seeing a steady cabin, with no discernible motion leads the eyes to declare that, ‘We are not moving.’ However, the ears’ fluid is sloshing around in response to gravity and other forces of physics and they let the brain know, ‘Yes, we are, we’re moving.’ Inside of a virtual world, the opposite happens – the eyes ‘think’ that they are moving, while the ears ‘know’ that they are not. In both cases, the disjunct between two sense that should be experiencing the same motion causes nausea and feelings of disorientation and illness. Those who do not suffer from motion or simulator sickness are simply those whose brain can overrule one of the senses, allowing the illusion of movement or non-movement respectively to continue.

Movement Making You Feeling Ill? Here’s Why motion sickness2

Simulator manufacturers introduced tilt platforms to allow a range of small movements to mimic the larger motions portrayed in the footage used in the test scenario. This works very well for most trainees, allowing their senses to send the same message to the brain, and making their training session a nicely realistic one for them. However, any lag, even of a few microseconds, between the perceived motion and the felt motion can be enough to upset the delicate balance between sight and balance, triggering nausea and illness. Therefore, it is vitally important that simulators are carefully calibrated so that the movements match up with the footage.

Movement Making You Feeling Ill? Here’s Why motion sickness3

With virtual reality sickness, there is little the user can do except hope that their brain will adapt. This is not as far-fetched or hopefully optimistic as it sounds. Developers say that the more VR is used, the more the brain will come to anticipate the disconnect between sight and balance – and that the mere act of putting on a headset will be enough for the brain to not respond to any imbalance. 

Movement Making You Feeling Ill? Here’s Why motion sickness4

Developers can do more – and they are working it. A surprisingly easy ‘cure’ has been to install a virtual ‘nose’ in the headset. It sits in our field of view where our real nose is, but inside the game, giving our brain a fixed point to hold onto, even as we explore space, fly fighter jets or race sports cars around capital cities.