Natural User Interface – Definition & Design Principles

An interesting aspect of interface design is Natural User Interface:

In computing, a natural user interface, or NUI, or Natural Interface is the common parlance used by designers and developers of human-machine interfaces to refer to a user interface that is effectively invisible, and remains invisible as the user continuously learns increasingly complex interactions. The word natural is used because most computer interfaces use artificial control devices whose operation has to be learned.1

The new interface devices for gaming are designed to make the interactions feel as “natural” as possible, removing the threshold for learning to operate them, letting the user focus on the actual application.

Mimicking the action/gesture on the screen to be able to play the game, removing the user’s threshold for learning to use the interface

To design applications for these new “Natural User Interfaces”, there’s several principles designers have to consider.
The following are eight principles designed by Rachel Hinman 2, Senior Research Scientist at Nokia Research Lab and author of The Mobile Frontier: A Guide for Designing Mobile Experiences:

  • Principle of Performance Aesthetics

    Unlike GUI experiences that focus on and celebrate accomplishment and task completion, NUI experiences focus on the joy of doing. NUI experiences should be like an ocean voyage; the pleasure comes from the interaction, not the accomplishment.

  • Principle of Direct Manipulation

    Unlike GUI interfaces, which are enabled by indirect manipulation through a keyboard and mouse, natural user interfaces enable users to interact directly with information objects. Touchscreens and gestural interaction functionality enable users to feel as if they are physically touching and manipulating information with their fingertips. Instead of what you see is what you get (WYSIWIG), successful NUI interfaces embody the principle of what you do is what you get.

  • Principle of Scaffolding

    Successful natural user interfaces feel intuitive and joyful to use. Information objects in a NUI behave in a manner that users intuitively expect. Unlike a successful GUI in which many options and commands are presented all at once and are depicted with very subtle hierarchy and visual emphasis, a successful NUI contains fewer options with interaction scaffolding. Scaffolding is a strong cue or guide that sets users’ expectations by giving them an indication of how the interaction will unfold.

    Good NUIs support users as they engage with the system and unfold or reveal themselves through actions in a natural fashion.

  • Principle of Contextual Environments

    One of the great things about natural user interfaces is that they are dynamic and can locate themselves in space and time. Unlike GUIs that will present a user with the same set of options regardless of the context, NUIs are responsive to the environment and suggest what the next interaction should be.

  • Principle of the Super Real

    Successful NUIs extend objects in a logical way into the world of magic, unlike GUIs that contain information in a cascading series of windows that resemble sheets of paper. With features like stretch to zoom, the UI elements of NUIs not only look real, but we also perceive them to be super real as their character can change in a way that is almost magical.

  • Principle of Social Interaction

    Unlike GUIs that are highly visual and often require a great deal of cognitive focus to use, NUIs are simpler and require less cognitive investment. Instead of getting lost in a labyrinth of menu options, menus on NUIs are streamlined, enabling more opportunities for users to engage and interact with other users instead of the system’s interface. As opposed to GUI laptops, which are optimized for individual use, systems with larger NUI formats, like the Microsoft Surface Table or tablets similar to the iPad, lend themselves to social computing experiences.

  • Principle of Spatial Relationships

    Unlike GUI systems, where an icon serves as visual representation of information, NUIs represent information as objects. In the world of successful natural user interfaces, a portion of an object often stands for the object itself. NUI objects are intelligent and have auras.

  • Principle of Seamlessness

    GUIs require a keyboard and mouse for interaction with computing systems. Touchscreens, sensors embedded in hardware, and the use of gestural UIs enable NUI interactions to feel seamless for users because the interactions are direct. There are fewer barriers between the user and information.

And several basic design principles from Dan Saffer’s book Designing Gestural Interfaces 3 that target touch interfaces, but apply to kinetic interfaces (like the Hydra, Kinect and Leap Motion) as well:

  • Design for Fingers, not Cursors

    Touch targets need to be much larger than for desktop: 8-10mm for tips, 10-14mm for finger pads.

  • Remember physiology and kinesiology

    Don’t make users do overextensions or repetitive tasks.

  • No gorilla arm

    Humans weren’t meant to do many tasks with hands up in front of their bodies for long periods of time. Sorry Minority Report.

  • Screen coverage

    Fingers are attached to a palm, which can cover the screen while you are trying to do a gesture. Avoid putting essential elements like labels below a control, as it can be obscured by the user’s own hand. Place items like menus at the bottom of the screen to avoid this phenomenon.

  • Know the technology

    The kind of touchscreen, sensor or camera determines the kind of gestures you can design for.

  • The more challenging the gesture, the fewer people who will be able to (or want to) perform it.

  • Trigger actions on release, not on press

  • Attraction affordance

    Use a simple gesture to get users to start using the system.

  • Avoid unintentional triggers

    A variety of everyday movements on the user’s part can accidentally trigger the system. Avoid.

  • Gestures and Command Keys

    Provide an easy (buttons, sliders, menu items, etc.) ways to access functionality, but provide advanced, learnable gestures as shortcuts.

  • Requisite variety

    There’s a wide range of ways to perform any gesture. Account for that.

  • Match the complexity of the gesture to the complexity and frequency of the task

    Simple, frequently used tasks should have equally simple gestures to trigger them.

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