A mistake leads me to close the wrong window.five: Human Error? No, Bad Design 205Now suppose I really intended to close a window. I often use atemporary file in a window to keep notes about the chapter I amworking on. When I am finished with it, I close it without saving itscontentsafter all, I am finished. But because I usually have multiple�windows open, it is very easy to close the wrong one. The computerassumes that all commands apply to the active windowthe�one where the last actions had been performed (and which containsthe text cursor). But if I reviewed the temporary window prior toclosing it, my visual attention is focused upon that window, andwhen I decide to close it, I forget that it is not the active windowfrom the computers point of view. So I issue the command to shut�the window, the computer presents me with a dialog box, askingfor confirmation, and I accept it, choosing the option not to savemy work. Because the dialog box was expected, I didnt bother to�read it. As a result, I closed the wrong window and worse, did notsave any of the typing, possibly losing considerable work. Warningmessages are surprisingly ineffective against mistakes (even nicerequests, such as the one shown in Chapter 4, Figure 4.6, page 143).Was this a mistake or a slip? Both. Issuing the closecommand��while the wrong window was active is a memory-lapse slip. Butdeciding not to read the dialog box and accepting it without savingthe contents is a mistake (two mistakes, actually).What can a designer do? Several things:
Make the item being acted upon more prominent. That is, change�the appearance of the actual object being acted upon to be more visible:enlarge it, or perhaps change its color.Make the operation reversible. If the person saves the content, no�harm is done except the annoyance of having to reopen the file. If theperson elects Dont Save, the system could secretly save the contents,�and the next time the person opened the file, it could ask whether itshould restore it to the latest condition.SENSIBILITY CHECKSElectronic systems have another advantage over mechanical ones:they can check to make sure that the requested operation is sensible.206 The Design of Everyday ThingsIt is amazing that in todays world, medical personnel can accidentally�request a radiation dose a thousand times larger thannormal and have the equipment meekly comply. In some cases, itisnt even possible for the operator to notice the error.�Similarly, errors in stating monetary sums can lead to disastrousresults, even though a quick glance at the amount would indicatethat something was badly off. For example, there are roughly 1,000Korean won to the US dollar. Suppose I wanted to transfer $1,000into a Korean bank account in won ($1,000 is roughly ?1,000,000).But suppose I enter the Korean number into the dollar field.
- Fall '19