Testing for power usability

Usability studies are usually conducted in a compressed time scale (measured in hours) compared with a user's eventual experience with a product (often measured in years). For this reason, typical usability evaluations focus on success during initial interactions with a product (sea for example Dumas & Redish, 1994 and Nielsen & Mack, 1994). Success on initial use is often driven by familiarity. Are what we call "intuitive" user interfaces really just familiar user interfaces? This "familiarity effect" can often swamp the usability differences between design alternatives. If usability evaluations continue to emphasize initial success with a product we may inhibit innovation in user interface design. There is a tension between initial usability (measured by success at first encounter) and efficiency of skilled performance. Initial learning of a product's user interface often results in quite rapid increases in efficiency of use. A narrow focus on initial usability elevates learnability above efficiency once "up the learning curve". While this approach is appropriate for some products targeted primarily for casual / occasional users, it fails to capture the usability issues associated with power users (those with significant experience, training, or a professional orientation to their interaction with the product).