The design of most objects and systems can be examined in terms of four layers of design.

Visual, Interface, Interaction, Motivation.

Visual layer

Visual elements of an objects and systems are typically their form, colour, texture, font, layout, styling. The design of vogue magazine is an example of visual design. The re-styling of the Ford Mondeo is visual design.

Interface layer

Interface elements of objects and systems are typically the parts that you touch. In the case of a kettle the handle is part of the interface. In the case of a software system the system of navigation, menu’s, drop downs, data entry areas, buttons, cursor hotspots are parts of the interface. Apple made a significant improvement to the interface design of mobile phones when they released the iPhone.

Interaction layer
Interaction elements of objects and systems refer to what occurs when the object is in use. A chair is sat on. A chair is also moved, purchased, knocked over, stood on, fallen of, restored. A website is read. A website is also built, maintained, skimmed over, found, contributed to, etc. The development of Web 2.0 technologies made a significant contribution to the development of the interaction design of social media.

Motivation layer
Motivation drives users to do things, to interact. A user who is motivated by the need for a cup of tea will interact with a kettle, a tap, teabags and a teapot. Alternatively the thirst for tea may motivate the user to visit a cafe and order tea and scones. Understanding the subtleties of motivation depends on the actors, the play and the context. The choice of a type of glass to drink from is a motivation layer problem. It is unlikely that a crystal wine glass will be used for milk shake in McDonalds. In software systems it is unlikely that a sales manager will use the CAD software although maybe he should.

Getting the layers mixed up
Sometimes the layers get mixed up. In system design huge effort can be spent fixing up the visual layer when the problem is really a motivation layer problem. In other contexts a huge process of self analysis in the motivation layer muddles and delays innovation in the interaction layer. Sometimes a visual freshen up is all that a product needs to give it a new lease of sales. Making a specific effort to understand the layer(s) that the design problem exists on is a good first step in exploring a new design challenge.