Welcome to Introduction to User Experience Design. In this lesson we will cover some features of good design. This design lexicon that is vocabulary used in user experience design describe features that are essential to a design being usable and useful. The terms I will introduce you to today are taken from Don Norman's influential book, Design of Everyday Things. This book was fist published over a quarter of a century ago. In this book, Norman provides examples of flawed design, these came to be know as Norman objects. One prime example was a poorly designed door. Worse yet, the notion of a Norman Door is not outdated. If you search, man crashes into glass door, you will see a number of videos that show that glass doors and automatic sliding doors are still causing all sorts of trouble. We can point to three design features that are often ignored in good design. These are affordances, signifiers and feedback. Next, we will consider what good design is and how they can be implemented. As we talked about in the last module, good design is a design that is usable. By usable we mean that it is characterized by being effective, efficient and satisfying to the user. Now I note that an interface is usable if the user can understand what input will lead to the desired output. For the rest of the lesson I will discuss these features as they relate to smartphones. Here, input is related to two terms we will cover shortly, affordances and signifiers. Usable design also requires that the output of the user's actions be visible. Here, we will talk about the third feature, feedback. Affordances refer to the perceived and actual properties of the things, primarily those fundamental properties that determine just how things could possibly be used. If you look at your smart phone we see all sorts of features for example, buttons, buttons are for pressing, the idea is that the affordance of the thought is to press. A term that Norman introduces in his new book that is closely related to affordance is signifiers, where as affordances tell us what actions are possible signifiers tell us where that action should take place. If you look at the screen of your smartphone, it has all sort of affordances that can be related to the gestures you make. You can tap, you can pan, you can stretch, you can flip the screen. But now imagine that you are bound to send a text, the digital keyboard appears and the letters signify where you must tap to activate those letters. The third design feature of usable design is feedback. Feedback requires sending back user information about what system input has occurred. It communicates the result of an action. In our example of texting the feedback mechanism is that the letter that we press appears in the text box, letting us know that we pressed the desired key. We've all experienced changing phones, and somehow not being able to press the correct key. When we see the wrong letter in the text box, it gives us feedback that we've entered the wrong, that we've pressed the wrong key. This concludes our module on features of good design. I look forward to seeing you in the next lesson. [SOUND]