Effective Visual Controls and the Minimum Noticeable Difference

On a recent trip to a market in southern China it occurred to me that there must be a thriving industry producing red ink in this country. By red ink I mean not financial losses but the literal wet and sanguine stuff that so much of the signage here seems to use. Red and yellow are the new black and white. No doubt only the wise judgment of this nation’s leaders that it would cause a critical shortage of red dye prevents newsprint and books from being printed on red paper.

There are cultural reasons for the ubiquity of the color red in China. Around the world many retail stores use bright red or yellow signs because the human eye is drawn to these more than other colors. Attractive images are used for the same reason. For the multi-billion dollar retail industries in which influence over human attention and interest is paramount, the scientific study of signage is taken seriously. To a greater or lesser degree, visual controls play a key part in our lives and work and understanding how to make them effective is important.

In the case of this stop sign a combination of color and shape are used to inform us of the meaning of this visual control. It is not necessary to be able to read Chinese to know this sign says “stop”. There is more information on this sign than a foreign visitor needs, yet there is enough to inform them to stop. In fact a sign without any writing, such as the one below, would have been sufficient.

The minimum distinguishable or noticeable difference in scientific terms refers to the smallest amount of light, concentration of chemicals, force or any information that is sufficient to make a difference in observation. In terms of visual controls, it is best to understand what accounts for the minimal noticeable difference and design the visual control with as little extraneous and distracting information as possible. In other words simple is best.

One could argue that in cultures such as China where there is so much red in signage that the minimum noticeable difference for a visual control such as a stop sign must be shape, not color. But one would be wrong. The stop sign itself is merely a decoration, a nod to conformity to international standards. The person making their way through the streets of China must deftly judge the size, speed and location of various moving objects while using the stop sign as a reminder at best, to temporarily increase vigilance.

Navigating traffic in China is a full-immersion activity that relies on the 5 senses plus a sense of balance, a sense of danger, and an awareness but not a naive trust in the effectiveness of visual controls.

1 Comment

  1. John Santomer

    November 2, 2010 - 10:35 pm

    Dear Jon,
    Ever wondered what that red spot on a dumpling meant? I see there are also black spots on some…Its a surprise fortune cookies never had any on them…

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