Interactivity design, on the other hand, addresses the entire interaction between user and computer. While it shares much with the study of user interface, interactivity design differs because it considers thinking in the process of optimization. The user interface designer optimizes the design towards the computer's strengths in speaking and listening, and away from its weaknesses in these same areas. The user interface designer never presumes to address the thinking content of software (the algorithms that determine its core behaviors).
Automated interactivity, made possible by the computer, has made possible a profoundly different kind of conversation. Human-to-human conversations are driven by the differences in knowledge or opinion of the conversers. While such differences may seem huge, they pale in comparison to the difference between human and computer, because the computer's thought processes are stupendously different from a human's. We can grasp emotional situations that a computer could never comprehend; the computer can multiply two numbers faster than we can read them.
Historically, the digital things made by interaction designers were largely tools – contraptions intended to be used instrumentally, for solving problems and carrying out tasks, and mostly to be used individually. Much of our ingrained best-practice knowledge in the field emanates from this time, expressed in concepts such as user goals, task flows, usability and utility. However, it turns out that digital technology in society today is mostly used for communication, i.e., as a medium. And as a medium, it has characteristics that set it apart from previously existing personal and mass communication media. For example, it lowers the thresholds of media production to include virtually anyone, it provides many-to-many communication with persistent records of all exchanges that transpire, and it offers access to ongoing modifications of its infrastructures.
Persistent use of any interface will cause you to develop habits that you will find yourself unable to avoid. Our mandate as designers is to create interfaces that do not allow habits to cause problems for the user. We must design interfaces that (1) deliberately take advantage of the human trait of habit development and (2) allow users to develop habits that smooth the flow of their work. The ideal humane interface would reduce the interface component of a user's work to benign habituation. Many of the problems that make products difficult and unpleasant to use are caused by human-machine design that fails to take into account the helpful and injurious properties of habit formation.
An interface is humane if it is responsive to human needs and considerate of human frailties. If you want to create a humane interface, you must have an understanding of the relevant information on how both humans and machines operate. In addition, you must cultivate in yourself a sensitivity to the difficulties that people experience. That is not necessarily a simple undertaking. We become accustomed to the ways that products work to the extent that we come to accept their methods as a given, even when their interfaces are unnecessarily complex, confusing, wasteful, and provocative of human error.
In her book, "100 Things Every Designer Needs to Know About People", Susan M. Weinschenk describes a mental model "as the representation that a person has in his or her mind about the object he is interacting with. A conceptual model is the actual model that is given to the person through the design and interface of the actual product." This is an important difference to understand. People create a mental model about an object or experience in an attempt to predict how the object will behave. Part of the design process involves understanding the user's mental model when he or she sees an interface or experience.
Everything people do is based on a pattern they have previously experienced and the expectation they have is based on those patterns. Some interaction designers call those patterns ‘mental models’ and use them to build ‘scenarios’ to predict how users will interaction with their designs. Mental models and scenarios are esoteric ways of saying that you should predict what your users expect and plan your response accordingly.
People are impossibly complicated, and designing interactions for them is even more so. You have to be a student of the world if you want to be successful, and that success will make you an expert in where ever your designs end up. However, being that expert does not always make you right. Good ideas can come from anyone and anywhere. Being humble enough to accept other ideas is paramount to your success.
Until the late 1970s, the only humans who interacted with computers were information technology professionals and dedicated hobbyists. This changed disruptively with the emergence of personal computing in the later 1970s. Personal computing, including both personal software (productivity applications, such as text editors and spreadsheets, and interactive computer games) and personal computer platforms (operating systems, programming languages, and hardware), made everyone in the world a potential computer user, and vividly highlighted the deficiencies of computers with respect to usability for those who wanted to use computers as tools.
In the 1960s, with the birth of cognitive psychology, the idea of "ergonomic fit"--a design fitting the human body--evolved into "cognitive fit"--a design taking into account and "fitting" the limits of our senses, deductive ability, and memory. This new concept of cognitive ergonomics was quickly incorporated into the burgeoning field of human computer interactions (HCI), which examined how human beings would interact with and use these radically powerful, new designed objects--computers.
Of course, interaction designs shouldn’t be merely useful. They should be fun. And part of that fun lies in finding systems that are both recognizable and challenging--that stretch our imaginations and lift us off the pixel plane. A good example of that comes via the Planetary iPad app by Bloom Studio, which allows you to browse your music collection as a system of planets and stars:
What do interaction designers need to know about visual design?
Visual design can be thought of as two interwoven parts: visual organization and personality. Visual organization utilizes the principles of perception (how we make sense of what we see) to construct a visual narrative. Through applications of contrast, visual designers can communicate the steps required to complete a task, the relationships between information, or the hierarchy between interface elements. So clearly visual organization is a key component for successful interface designs.