Many organizations utilize the paper prototyping technique for assessing the mobile user testing. It is an inexpensive technique and allows testing real users. This is imperative at the testing stage to avoid the expensive changes that need to be fixed.
What is Paper Prototyping?
Paper prototyping involves users performing relevant tasks by interacting with the paper prototype of the interface, where manipulations are being done by a person 'behaving as a computer', without informing the user about the manner of functioning of the interface. The facilitator then guides the user through the design interface by asking various questions and notifying the feedback. This technique can be used for computer interface such as a software, website or mobile device, and feedback can be elicited quite quickly in real-time. Apart from usability testing, product teams can use it to come up with design ideas and test internal interface.
Why Paper Prototyping?
Paper prototyping is a cost-effective and fast technique to test usability of the design process. It is often overlooked by designers who do not trust it's efficiency in getting all of the information. The designers prefer to wait for a better interface to demonstrate to users. This approach can be detrimental with respect to feedback required for usability testing at early stages of development. Early feedback on usability can help in making minute alterations to user interface without affecting the final user experience.
It is always beneficial to test the ability at the initial stages of the design process. It greatly enhances the design metrics. Doing this early at low cost explains the essence of paper prototyping, even though paper prototype might not appear to be a good option for testing a fully matured design. Paper prototyping continues to remain an effective technique for the coming years, as it does not get technologically obsolete, and can be safely applied to every project. (2)
Paper prototyping is here to stay. It requires no coding and helps in analyzing the diversity of issues related to user interface based on feedback from users. A diverse team rich in competency and skill sets can participate, leading to instilling creativity in the product time fueled by user participation.
In turn, the process inculcates iterative development methodology, and helps in developing the correct product by raising the issues long before the implementation stage.
Problems Associated with Paper Prototyping
Although an inexpensive methodology for mobile usability testing, it ignores the physical, sensory, and emotional aspect of holding the device. The design also appeals to the intrusive level of cognition. Usability testing should involve testing the artistic appeal of the design, which defines it's uniqueness. Since emotional engagement affects the human-interface involvment from physical, artistic, and usability perspective, a system is required that can explain both the physical and emotional level of user experience of the interface. Paper prototype is exclusively in capturing the emotional experience of the user, leading to a better assessment of user feedback.
Issue Resolution – Paper-In-Screen Prototyping
The mid path that can overreach the issue of testing emotional engagement of users is through paper-in-screen prototyping techniques for mobile usability testing. This involves designing paper screens, capturing their images, and displaying them through mobile device, thenby allowing users to actually touch and manipulate. It allows capturing the emotional response of users to assess the usability of design since the mobile device is used as a medium of self-expression, and users refer to mobile physically.
As pointed out by Don Norman, in his book Emotional Design, the visceral level of design (along with reflective and behavioral) is an important criterion to anticipate the real mobile user experience. The entire gamut sensory experience elements – look, touch, and sound effects user experience. The paper-in-screen prototype enables testing user experience at visceral, behavioral, and reflective level through a real mobile device in an inexpensive way.
Steps to Create Paper-in-Screen Prototype
1. Drawing and sketching the actual paper prototypes as done in a regular manner.
2. Taking digital images of the prototype or scanning it.
3. Making the necessary modification to the digital images to fit into the mobile device involved in testing.
4. Arranging images in folders in a sequential manner so that the actual screen illustration sequence is displayed and the images are in a predefined scenario. Every folder will contain the album of images that are uploaded to the mobile device.
5. Testing user interaction by allowing the user to browse each folder and it's sequence of images.
Advantages of Paper-in-Screen Prototype
The paper-in-screen is quite interactive and suited for early design testing and provides enhanced user feedback, compared to paper prototype. This is due to it's ability to estimate a higher level of user experience, although the process is more difficult due to the inability to document feedback as done in paper prototype. The paper-in-screen technique rests in between low and high fidelity prototyping with respect to the trade-off between the depth of test experience and the quickness with which prototypes can be developed. It allows for context based user experience capture in a realistic environment by including visceral and behavioral elements of design and a higher degree of interactivity.
The techniques involve a defined pattern of browsing a scenario, leading to linear experience, which prohibits natural and unprompted actions. A mechanism allowing scanning of image files of a paper prototype with a 'clicking feature' for users could greatly enhance the interactive and realistic nature of paper-in-screen prototyping. 
The paper-in-screen prototype aims to bridge the gap between a high fidelity and low fidelity prototype. It is cost and time efficient and highly portable across multiple devices. It has better feedback eliciting capacity across a variety of ideas and can be explored across various interfaces.
(4, 5) Bolchini, D., Pulido, D., Faiola, A. “++” Paper In Screen “Prototyping: An Agile Technique To Anticipate The Mobile Experience [Bolchini, D. et al].” 03 February 2010. ECA Website. 23 February 2020
2 Neilsen, Jakob. “Paper Prototyping: Getting User Data Before You Code.” 14 April 2020. Neilsen Norman Group Website. 23 February 2020
(6, 7, 8) Pulido, Deigo. “Paper-in-Screen Prototyping.” 12 April 2011. UX Magazine Website. 23 February 2020
 Snyder, Carolyn. “What is paper Prototyping?” 16 April 20o3. Paper Prototyping Website. 23 February 2020
(3) “What is Paper Protyping – Pros and Cons.” 16 April 2003. Paper Prototyping website. 23 February 2020