An affordance is a relationship between the properties of an object and the capabilities of the user that determine the different uses that can be given to said object. The transparency of the glass affords to let light through, but it does not afford for physical particles to go through, so a wine glass affords not only to contain something, but also to easily see it. Affordances need to be visible in order to provide strong clues to the operations of things without the need for labels or instructions. These unwritten clues are called signifiers.

Signifiers are indicators of any type that communicate the action needed so the affordance can take place, and it’s a term that’s widely used in the field of semiotics. For example, a door has the affordance of opening and closing. But how do we know how to do this? How do we know how if we have to push, pull or slide? For the most part, handles tell us.

Those are the door’s signifiers in relation to the affordance of closing and opening it. A large horizontal bar lets us know that we need to push it, while a handle lets us know we need to pull it. To function in the world, we need to develop internal models of what things mean and how they operate, and signifiers help us with that.

Constraints are limitations or restrictions, and they give us clues that allow us to determine a course of action by limiting the possible actions available to us. According to Norman, there are 4 types of constraints:

Physical – This pertains to the limitations caused by physical features such as size and shape.

Cultural – Restrictions that are a consequence of what is socially and culturally deemed as acceptable behavior.

Semantical – Limitations that rely upon the meaning of the situation to control the set of possible actions.

Logical – A type of constraint that comes to our attention because of its obviousness or because our logic was violated. The last piece of the puzzle must go in the only space left and if we have a bolt left after assembling a piece of furniture, then we must have made a mistake because the bolt must go somewhere.

Mapping is a mathematical term synonymous with function, which is a relationship between a set of inputs and a set of permissible outputs. For instance, to turn the volume of the tv up (turning the tv’s volume up or down is an affordance of the remote), first we look for the volume button (a signifier that communicates the remote’s affordance of volume control) and then we press up if we want the volume louder or down if we want it softer.

This relationship between up / loud and down / soft is mapping, and it works best by naturally taking advantage of spatial analogies, like in the case of the remote.

Feedback happens when an object or system notifies the user that it is working towards the completion of its objective. A clear example of this is elevators. When we press the button to call an elevator, it tells us that it’s on its way by lighting up. However, it’s not the most effective feedback because it doesn’t let us know how long we will have to wait, and this uncertainty causes users some discomfort. Good design gives back clear feedback in order to avoid any type of discomfort or difficulty.

Conceptual model is a synonym for a psychological term called association, which refers to a connection between conceptual entities or mental states that result from the similarity between those states or their proximity in space or time. In the words of Don Norman, “a conceptual model is an explanation, usually highly simplified, of how something works. It doesn’t have to be complete or even accurate as long as it is useful”.

He illustrates his point with an excellent example of the folder shaped icons found in our computers; Computers don’t have folders, however, designing the icons as folders makes it easier for us to conceptually understand how computers store information by allowing us to make an association with something that is familiar to us. This association is what allows effective communication between user and object, bringing the design one step closer to success.

A collection of success stories can be found at Erdmann.ch