Six fundamental psychological concepts for designing good products: Affordances, signifiers, constraints, mappings, feedback, and conceptual models.
In Discoverability and Understanding from I/O#62, we learned one of the essential characteristics of good design: discoverability (how easy it is to identify what actions are possible and know where and how to perform them).
Good discoverability relies on the following six fundamental psychological concepts:
Affordances indicate possible actions.
An affordance is a relationship between the properties of an object and the capabilities of the agent that determine how objects can be used.
For example, chairs afford sitting, buttons afford pressing, and handles afford pulling. A good affordance clearly shows the intended use without instructions.
Affordance is not a property but a relationship that depends on both the object and the agent. If an affordance is not perceivable, a signifier is needed to indicate its presence.
Signifiers guide you exactly where to perform an action.
For example, a flat door plate signals "push". Signifiers convey information about possible actions and how they should be done.
For signifiers to be effective, they must be easily perceivable. Otherwise, they fail to serve their purpose.
Distinguishing between signifiers and affordances can be challenging. The way I understand it is that "affordances define what actions are possible, while signifiers indicate where those actions should take place."
Constraints limit mistakes by restricting actions.
They limit our choices to guide us effortlessly. There are roughly four types of constraints:
- Physical Constraints: USB connectors fit only one way.
- Cultural Constraints: Red traffic lights universally mean "stop."
- Semantic Constraints: Motorcycle windshields imply riders face forward.
- Logical Constraints: Switches placed logically next to corresponding lights.
Mappings connect controls and their effects.
For example, imagine a classroom or auditorium with numerous ceiling lights and a row of light switches located on the front wall. Each switch controls a specific light, and this mapping defines which switch operates which light.
A good mapping to identify which control corresponds to each light in a large space is to arrange the controls in the same pattern as the lights. This also applies to stove knobs: If the knobs match the burner positions, turning on the correct burner is easy.
Feedback provides immediate clarity after actions.
For example, hearing a door shut, clicking a mouse, or seeing an icon change provides clear feedback. This feedback should be immediate because even a delay of just a tenth of a second can be disorienting. If the delay is too long, users may lose interest and move on to other activities.
Moreover, feedback must be informative. Feedback that is either vague or incorrect does not help the user.
However, it's important to note that too much feedback can be just as frustrating as too little. The annoyance caused by a "backseat driver" is widely recognized.
While backseat drivers may be correct, their constant comments can become distracting rather than helpful. Similarly, machines that provide excessive feedback can act like backseat drivers, ultimately hurting the user's experience.
Conceptual Models help users understand systems intuitively.
A conceptual model is a simplified explanation of how something functions.
It doesn't need to be complete or entirely accurate as long as it is useful.
For example, the files, folders, and icons displayed on a computer screen help users create a mental model of documents and folders stored on the computer. However, in reality, there are no physical folders inside the computer. These are just effective representations designed to enhance usability.
Designers must ensure that their conceptual models align with those of their users. That's why designers should always talk directly to the user to make sure their conceptual models are aligned.