Motion Sickness and Sword Art Online

Motion Sickness in VR games like Sword Art Online

Sword Art online or SAO has a number of different scientific and technological issues that I can explore. The most popular of these topics, specifically the possibility of having a real life version of SAO, will not be explored today. My reason for this is because I am not an expert on computers, it needs technology that has yet to be invented, and well I think it’s been done to death already. Today we will looking at motion sickness in VR games, and how it relates to SAO.

Vestibular System

Before tackling motion sickness in VR games also known as kinetosis or travelers sickness, we need to know how the human body detects motion. The vestibular system, is the part of the human sensory system that detects motion and spatial awareness. The vestibular system is broken into two parts, the eye provides visual detection of movement, and the inner ear which detects changes in acceleration. Also all of the nerves for these sensory systems run directly to and from the brain and do not enter the spinal cord.

motion sickness in VR games
Sense of balance

The signals from the eyes are processed in the occipital lobe of the brain, and used to determine if the body is moving. The second and less well known part of the system is the inner ear specifically the vestibule and semicircular canal.

motion sickness in VR games

The vestibule detects the body’s orientation in space. Basically the vestibule is why you always know which way is up after being spun around, underwater, in an avalanche or any other situation. The semicircular canals on the other hand detect angular acceleration of the head, vertical (nod your head up and down), horizontal (rotate the head side to side) and lateral (nod your head to the left and right). The brain then combines information from both of these system to determine if the body is moving.

Causes of Motion Sickness

There are currently three different causes for motion sickness, two of these involve the stretching of muscles and nerves involved in the vestibular system, and are not relevant to the current discussion. The third and most common cause of motion sickness, is a disconnection between the two halves of the vestibular system. Simplified what this means is that the eyes detect motion, and the vestibular system does not, or the eyes do not detect motion and the vestibular system does. The body’s response to this disconnection, is to become nauseas and in many cases induce vomiting. Before you think that this is just some quirk of our biology, there is an evolutionary basis for this response. Many plants contain various neurotoxins, which can cause visual hallucinations, and expelling these plants before they killed you would be a good thing.

Connection to SAO

Now what does all of this have to do with SAO, well a lot if you think about it. Nerve gear the advanced technology that makes a VR game like SAO possible is explained to use advanced technology to block nerve signals from traveling into or out of the brain via the spinal cord. This is so the individual can run and move around in the game without moving their body in the real world. A face plate provides the visual information so the player can see what they are doing.

Nerve gear
Nerve gear

Specifically the nerve gear is explained as stimulating the five senses, sight, sound, taste, touch, and hearing. There is no mention of a sense of motion. Thus as explained, the nerve gear is setting people for developing motion sickness in VR games like SAO, as they would see motion, but not feel it. The degree to which people will develop motion sickness will vary as some are more susceptible than others. Thus the ability of SAO to completely replicate a virtual environment is busted.


However I am more than willing to give Reki Kawahara a on motion sickness in VR games because, A I think SAO is pretty darn cool, and B he most likely isn’t a science person and did not have knowledge of this in the first place. FYI Dot Hack Sign would also have the same problem. Please leave any comments or questions you have in the comments section below.

Update 04/27/2018- SAO Progressive

I have been reading SAO progressive light novels recently and Kirito makes a comment about motion sickness in VR games during the 3rd novel which takes place on the 4th floor which is a level filled with lakes and canals. His comment was that if he was in the real world he would have gotten motion sick while staying in a town that was built on the water. His reasoning is that he can’t feel the movement in his inner ear. This is interesting because Reki Kawahara is mentioning one of the two body systems that deal with motion, and in this case Kirito would be correct because he won’t feel the motion of the boats on the water that he can’t see. It is interesting that no mention has been make so far about seeing movement and not feeling it.


3 thoughts on “Motion Sickness and Sword Art Online

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