I moved recently to the university housing. One hot day, I turned on the air conditioner, and spontaneously turned temperature knob to the lowest setting. But soon I found something is wrong. It was not cool. What was problem? It was the large title saying “Temperature” that caused mismatch between my mind and the designer’s mind. When we say temperature, isn’t low temperature is cooler? However in this case there is a small caption saying “Max Cool” at the highest temperature setting. It apparently shows the conflict between the working control and the working model in user’s mind. It is also sad that a usability test in the real world setting can easily detect this problem and the fix was easy to implement because it is just change of the silk screen print.