Shape-changing interfaces (SCIs) dynamically alter their form, an inherent characteristic that introduces fragility into their design. As a result, users’ perceptions of an interface’s fragility or its potential to move or break may influence their interaction, however the extent of this effect is unclear. To address this gap, we conducted a qualitative study (N = 18) using video stimuli showcasing 20 existing SCIs. Through thematic analysis, we identified key factors impacting perceived fragility and formalized these into a framework. We then conducted a second study (N = 36) for which we fabricated SCIs that varied across selected fragility-related dimensions. We recorded user interactions and compared how the selected dimensions shaped manipulation of the objects and how they were considered by users. Together, these studies provide a structured foundational understanding of perceived fragility in SCIs and offer insights to enhance perceived robustness and inform future SCI development.

Everyday users are confronted with increasingly complex technologies, be that novel introductions or ever-changing and expanding familiar interfaces. This creates the challenge of users needing to perpetually discover new functionality and interactivity, which is rarely addressed when novel technology is proposed. A possible contributing factor for this is the variety of, often inconsistently defined, associated concepts and a consequent lack of clarity on how to address these problems. We examine usage and definitions of discoverability as well as related concepts and offer clarifications where definitions are ambiguous while highlighting focus areas and limitations. In doing so, we provide a clear definition of discoverability, underscore the separation of system, feature and interaction discoverability and elucidate how other concepts focused on initial interactions differ.

Figure 1: Interaction signifiers are embedded in animated transitions to temporarily expose users to swipe-revealed hidden widgets, or swhidgets, as a means to increase their discoverability.The swhidget interaction is hidden in the application view (middle).A user then swipes an email away from the edge of the touch screen to reveal the hidden buttons.

Touch screens supporting different inputs such as 'Tap', 'Dwell', 'Double Tap' and 'Force Press' are omnipresent in modern devices and yet this variety of interaction opportunities is rarely communicated to the user. Without visual signifiers, these potentially useful inputs remain unknown or underutilised. We propose a design space of visual signifier characteristics that may impact the perception of in-place one finger inputs. We generated 36 designs and investigated their perception in an online survey (N=32) and an interactive experiment (N=24). The results suggest that visual signifiers increase the perception of input possibilities beyond 'Tap', and reduce perceived mental effort for participants, who also prefer added visual signifiers over a baseline. Our work informs how future touch-based interfaces could be designed to better communicate in-place single finger input possibilities.