In computing, a natural user interface (NUI) or natural interface is 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. Examples include voice assistants, such as Alexa and Siri, touch and multitouch interactions on today's mobile phones and tablets, but also touch interfaces invisibly integrated into the textiles of furniture.[1]
An NUI relies on a user being able to quickly transition from novice to expert. While the interface requires learning, that learning is eased through design which gives the user the feeling that they are instantly and continuously successful. Thus, "natural" refers to a goal in the user experience – that the interaction comes naturally, while interacting with the technology, rather than that the interface itself is natural. This is contrasted with the idea of an intuitive interface, referring to one that can be used without previous learning.
Several design strategies have been proposed which have met this goal to varying degrees of success. One strategy is the use of a "reality user interface" ("RUI"),[2] also known as "reality-based interfaces" (RBI) methods. One example of an RUI strategy is to use a wearable computer to render real-world objects "clickable", i.e. so that the wearer can click on any everyday object so as to make it function as a hyperlink, thus merging cyberspace and the real world. Because the term "natural" is evocative of the "natural world", RBI are often confused for NUI, when in fact they are merely one means of achieving it.
One example of a strategy for designing a NUI not based in RBI is the strict limiting of functionality and customization, so that users have very little to learn in the operation of a device. Provided that the default capabilities match the user's goals, the interface is effortless to use. This is an overarching design strategy in Apple's iOS.[citation needed] Because this design is coincident with a direct-touch display, non-designers commonly misattribute the effortlessness of interacting with the device to that multi-touch display, and not to the design of the software where it actually resides.