Designing the Real World

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May 2004. Online

Left or right

When John was studying medicine, his group had a headless cadaver to dissect in anatomy lessons. John used to spend hours cutting and isolating skin and organs while listening to the lecturer; ‘notice the organs relationship to the right lung...’. For months he was told what to do on the left and right sides of this body, but the left and right of this body were the exact opposite of his own left and right. Eventually he lost track and would get confused about left and right when he was back in the ‘real world’.

Surgeons must find ways of switching between the two frames of reference; that of self and patient. This issue of self or patient as the reference point is echoed by the situation where a group of people are talking about something big surrounding them such as a ship or an airplane. Just as there could be mismatches between the self and patient frames of reference so too there can be mismatches between the self and vehicle frames of reference. This is one of the reasons that some vehicles use the terms ‘port’ and ‘starboard’. There was one airplane crash where this convention broke down; there was engine trouble, the co-pilot turned in his seat to try and see the engines through the windows and told the pilot which one it was . Instead of using port and starboard he used left and right and because he was twisted round so that his left and right were opposite to those of the plane there was confusion and the pilot ended up shutting down the good engine instead of the bad engine.

This confusion between self and vehicle frames of reference also comes about with coach tour guides; they stand at the front of the coach facing the passengers and say ‘to the left is the Cathedral’. Experienced tour guides know how to clarify the problem and tie their commentary into the passengers frame of reference; ‘on your left is the Cathedral’.

A more grisly example of the left and right confusion with bodies facing you was the account of an operation in a Dutch hospital several years ago where a young man with blood poisoning in his foot had to have his leg amputated below the knee. Only when he was recovering post-op did he realize that they had amputated the wrong leg. By the time they could get him back in again the shock of the double amputation coupled with the continued blood-poisoning meant that he died shortly after the second operation.

The other area of interaction design where left and right play a vital part is in the design of products and systems that depend on which hand the user favors. Most people know about the problems of scissors for left and right handed people. If you don’t then you are probably right handed, go and get an ordinary pair of scissors and try using them in your left hand – they just don’t cut properly. It is not just scissors, left handed people have all sorts of disadvantages when using tools and systems set up for right handers. Even something as simple as the drinks stations for marathon runners can cause problems, they are set up for runners to reach out with their right hand and grab a drink in passing. Tricky if you are doing it at high speed, when tired and using the hand that you hardly use for anything else.

As far back as medieval times the designers (or ‘master builders’ as they were then) were aware of this difference. Visit any church or castle in Europe next time you are there and you will probably find a spiral staircase or two. Most of them spiral anti-clock wise as they go down (and thus clockwise as they go up). Apparently this was to favor defensive sword use should the building be overrun at any time. If you are up the spiral stair and are right handed and facing down the stairs you will have the central axis of the stairs on your left and you will be able to swing your sword at your foe coming up the stairs. He on the other hand will have the central axis on his right and so it will be directly in the way of his sword swings. There is enough contemporaneous information to back up which hand swordsmen used to use in those days, but what about earlier times. Have we always been mainly right handed? Well, there was an interesting discovery recently of cave paintings and hand outlines. As part of the painting ancient man would put his hand on the wall, spatter paint at it and then remove it, resulting in a silhouette of his hand on the wall, surrounded by spatters. Most of these hand prints were of the left hand thus, assuming that the right hand was actively doing the spattering of the paint, we can draw the conclusion that early man was also predominantly right-handed.

As well as the left and right problems with dead bodies that I opened with, there is also a frightening front and back confusion that can arise with half-dead bodies. In the early days of motorbike riding, before they had all the special gear, riders would try and stop the high-speed drafts getting through their coat fastenings by putting their coats on back to front so that the fastenings were on their back. This was fine and warm, the only worry being that if you came off you bike and were lying unconscious by the side of the road some helpful soul might think your head had been twisted right round in the crash and try and twist it back again!

So, left-right considerations are important when you are designing large symmetrical structures with people in them, and they are important when designing things for people to use with one hand. There are probably other situations where a consideration of left-right issues are important but they will only become apparent in hindsight. The best policy is to add a ‘left-right issues’ check box to your design check list and and consider it, however briefly, for every design project that you work on.

... but which side of the text should you put the check box on?