Discrepancy between real life and mental model

Norman (2013) stated that "mental models are the conceptual models in people’s minds that represent their understanding of how things work." (pg. 26). Thus, people may have different understanding of how a product will operate even though they have used the similar product everyday because every product might have different operations. Like the heater below, the operation is totally different from my heater; this heater requires simultaneous depression of two things, which have been labeled as "1" and "2". However, because my understanding of how heater works does not correspond to this heater when I used it, I could not figure out what to do when the heater did not operate well to my expectation. Therefore, the following paragraphs will clearly indicate my experience in using this heater,

Image 1

That day was the first time I used this kind of heater. My house, definitely, has a heater, but my heater is very simple because I only need to press on a red button to heat up the water, and I can use the hot water after that. 

Before using the heater, my friend has asked me if she needed to teach me how to use, but I rejected her kindness because after looking at the heater I thought that it would be very easy as I just needed to press the bottom silver button that has been labeled as “2” to turn on the heater and turn the tap that has been labeled as “1” and the water will come out itself. The reason I knew that I should press the bottom silver button was because the word “push on-off” on the bottom silver button has already communicated the message that the button is used to on or off something. 

Also, I didn’t think that I should change the temperature of water because my friend likes to bath with hot water.  

Thus, I pressed the bottom silver button, and turned the tap but the water did not come out, and I was totally shocked because I believed that the method that I have figured out to on this heater was correct.  

Then, I tried to press other buttons, but nothing worked in my way. Although from the image on the right, you could have noticed that the heater has a power indicator that can allow me to see if I have on the heater properly. However, at that time I did not notice the power indicator as I did not know the heater will have the power indicator, which influence me not to focus on that part. Then, I simply pressed anything and turn the tap on and off and suddenly the water came out.

Looking at the image below, can you differentiate in which direction the tap is on? And in which direction the tap is off? 

Image A

Image B

For the water to come out from the shower, two conditions must be met: 1) The heater must be on, and 2) The tap must be at the right position (which is in the same direction in image A) instead of the left position.  Because these two conditions should be met at the same time, if you go in to the bathroom, and the tap is in the same direction as image, you will automatically turn it to the other direction because you might assume that the tap is off in that direction because other typical heaters only affects the water temperature and the only factor affecting water coming out from the shower is the tap. In my opinion, this heater should have been designed similarly to the other heaters to prevent confusion to other users. Also, my friend’s family will not develop the habit to just off the bottom silver button on the heater without closing the tap. And, if my friend has closed the tap properly I would have never faced any problem in using the heater that day. 

Reference:
Norman, D. (2013). The design of everyday things: revise and expanded edition. Available from http://cc.droolcup.com/wp-content/uploads/2015/07/The-Design-of-Everyday-Things-Revised-and-Expanded-Edition.pdf