Design for People

As a software engineer one has to make design decisions. I always ask my fellow engineers to keep the people factor in mind. The decision should follow the principle of least astonishment(POLA). To explain the POLA I am going to take a real world example. It is easy to remember real world examples better.

In the recent times I have accumulated lot of mobile devices. Out of them I am going to take only the following 3 devices

  • Nexus 7
  • Samsung Galaxy s3
  • Apple ipad

I myself and my family members use them interchangeably. One of the major use case is to adjust the volume. After using these devices I know that the volume button is somewhere in the side. I try to use the muscle memory, search for it and adjust the volume. But the experience differ between the devices. I will list them in the order of worst to best.

  • Nexus 7 – This the worst one among all the three. The volume and power button are placed on the right hand side. I tend to push the power button instead of the volume button and then press the power button again and get back to volume control. For a human being its hard to remember the exact location of the button unless otherwise one is using the same device for a long time.
  • Samsung Galaxy 3 – In GS3 the volume buttons are on the left hand side and the power button is on the right hand side. Even though this looks better, again correctly remembering the type of button and left/right side is hard. I tend to do the same thing here too. I press the volume button and course correct later.
  • Apple ipad – Here the volume buttons are placed on the right hand side. The power button is placed on the top. There are couple of advantages here.
    • In the above 2 cases I actually cross checked the devices for correctness of my post. In case of ipad it was not needed. I can remember top & sides. But its not easy to remember whats on left & right.
    • I always end up pressing the volume button and never enter an alternate operation by mistake.
    • This provides the best experience for me.

Now the third case of ipad satisfies the principle of least astonishment. In the other 2 cases I intend to do something, but end up doing something else and then after a moment of surprise I course correct. Now if you are an engineer make sure the design decisions follow the principle of least astonishment. It definitely saves lot of time for your fellow engineer/human being.

To give an example from the software side guess what the following object represents

var d = new Date(2011,1,23);

Any one would make a guess that it represents 23 January 2011. But if you are programming in JavaScript then it represents 23 February 2011. While the date and year start from 1, the month start from 0. When I was programming in JavaScript the question I had was hours,minutes,seconds all start from 0. That is natural. But why does month start from a 0? That was my moment of surprise.

Hope you consider the people first when making the design decisions.


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