The Successful Experience Pyramid (SEP), as a method to measure a system's trustworthiness, is based on the user's total sense of success when interacting with the app.
Why is trustworthiness important? Trust represents a higher-level of user experience. It's what makes a 'good' user experience. It is also the key in persuasive design, which goes beyond good usability, and is what ultimately makes a system useful and meaningful.
Anyone who's ever dealt with user feedback probably has seen how users can finish a task but did not think they did. While conducting my usability study for a class at UMD, I observed the same and thought about how best to represent evaluating the objective user interaction (e.g. task completion rate) and the subjective (e.g. self-reporting of success).
As an answer to that thought, I developed this heuristic model to take both into account. I decided on the pyramid analogy to illustrate a holistic examination of an user experience. Without any single layer or component, the total experience will be fragmented and ultimately unstable.
The model, which has ideas rooted in Nielsen's 10 heuristics, Dan Saffer's Designing for Interaction and other usability research, is constructed with three layers and four components. Two cornerstones of good UX - affordance and appropriateness makes up the foundational layer. The middle layer is user control and confidence, which cannot exist with the two basic components. Then, as the pyramid solidifies to its apex, perceived intelligence, the users' sense of success and their perception of the system's trustworthiness should increase accordingly.
SEP Model Explained:
Good affordance means the system's behavior matches the user's mental model. Before interacting with the system, users should know what to expect from an action, i.e. good signals or scent. After taking an action, the system should give the expected feedback signals. Consistency and clear use of metaphors all contribute to positive affordance. (additional good reads on affordance)
The aesthetic of a design should be as complex or as simple as it needs to be. It should also be representative of the system's targeted experience. This is similar to Apple's notion of aesthetic integrity. While decorative elements should be used with caution, a successful system does not mean one without any elements to enhance its visual appeal.
User Control and Confidence:
User should never feel trapped within the system. She should have a sense of control. More importantly, she should feel confident in her actions which lead to more active exploration
and learning of the system. Reliability of the foundational layer is key to the solidity of this component.
This is the apex of the pyramid. It combines two design principles - smart and cleverness. A system is perceived as intelligent if it effectively anticipates the user interaction, errors, and needs. Moreover, it should be able to handle tasks not easily done by users. An example would be error prevention schemes.