Question 1:

In your own words, write a summary of the article and provide critical analysis/ discussion on the  topic of the article (300 – 350 words)

“Consistency” is an article that is written by Lidwell, Holden and Butler in 2003 that describes it as systems being usable and learnable when similar parts are expressed in similar ways. (Lidwell, Holden, & Butler, 2003). The articles state that consistency allows the user to easily learn new things, whilst also being able to transfer knowledge that they’ve previously already known to the new context. Consistency can be categorised into 4 different categories. These are aesthetic, functional, internal, and external.

The consistency of style and appearance is what is known as aesthetic consistency. It enhances recognition, and creates a identifiable uniformed community allowing those who have previously bought products from them to continue being loyal to the company. For example Apple. If you buy their iPhone, you would also want their iPad and iMac to be able to easily sync from product to product. Their logo is in the simple shape of a bitten apple, allowing customers to associate it with the simplicity and prestige in their products.

Functional consistency refers to the consistency of meaning and action. This principle improves the usability and learnability of a person by allowing them to use their existing knowledge to understand how the design functions. Take a look at media controlled devices we see around today, we automatically know that the red button with the white circle is for recording, the big triangular button to play, square button to stop, two rectangles to pause and two triangles facing either direction to rewind or fast forward. The consistent use of these symbols allows user to put their existing knowledge towards new products, reducing the time to learn how to use it. (Lidwell, Holden & Butler, 2003).

Internal consistency refers to the consistency of working with other elements in the system. It relates to designs such as pictograms; “a symbol which represents a person or object” (Baines & Haslam, 2005). Examples include a picture of food or cigarette with a red cross over it telling people not to eat or smoke in that area. These signs are similar no matter which part of the world you are in and are used for self awareness or to allow you to know their rules especially if you’re in a new place.

External consistency refers to consistency with other elements in the environment.  This principle extends benefits towards internal consistency of multiple and independent systems. Franchise businesses around the world for example, develop rules, guidelines, equipment and customer service (H&M, McDonalds) to provide the same product around the world. (Barry, 2013).

All systems should always be both internally and externally consistent. Aesthetic and Functional consistency should also always be considered when creating a new product.

Question 2:

Study 3 examples (e.g. products found in everyday surroundings) that meet the aesthetic‐usability  effect principle.

A traffic light makes use of functional consistency. This consistency is evident through the colours used in the lights. It is universal knowledge that red means stop, green means go, and yellow means slow down. People all over the world use these colours in traffic lights no matter what because everyone knows it means the same thing everywhere.

Figure 1 – Traffic Light

Remote controls are another product that meet this principle. Aesthetic consistency is noted throughout all forms of remote controls because they all look similar with identical purposes. Its fucntional consistency is evident when users apply their previous knowledge from each control to another. The buttons on in all signify the same action on each remote, the red button with the white circle is for recording, the big triangular button to play, square button to stop, two rectangles to pause and two triangles facing either direction to rewind or fast forward. This also comes in conjunction with external consistency seeing as all companies use these same buttons globally.

Figure 2 – Range of Remote Controls

The iPhone is a product that makes use of aesthetic and  external consistency. iPhones have been around since 2007, but till this day, nothing about its design has had a massive change. Each iPhone, from the first to the 6s, consist of the same buttons, same way to unlock and similar looking design. But no matter what it still looks the same, give or take the size and weight. It isn’t only the design of the body of the phone that looked the same over the years, but also its functionality and placement of the apps as seen in Figure 3.

Figure 3 - iPhones over the years
Figure 3 – iPhones over the years


Baines, P., & Haslam, A. (2005). Type and typography (2nd ed). London: Laurence King.

Barry, N. (2013). What is Aesthetic, Functional, Internal, External: Consistency?. [Blog Post]. Retrieved from 

Falkner, N (2012). Consistency: Doing The Same Thing Can Be Useful!. [Blog Post]. Retrieved from

Lidwell, W., Holden, K., & Butler, J. (2003). Aesthetic Usability Effect. In Universal Principles of Design (pp. 46). Massachusetts: Rockport.

Jason Whitlock. (2014). SMART Traffic Signals Soon Coming to Little Rock. Retrieved from

Slashgear. (2013). iPhone Comp. Retrieved from

Wikipedia. Remote controls for devices. Retrieved from

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