Investigating the affective quality of interactivity by motion feedback in mobile touchscreen user interfaces

Abstract

Emotion is a key aspect of user experience. To design a user interface for positive emotional experience, the affective quality of the user interface needs to be carefully considered. A major factor of affective quality in today's user interface for digital media is interactivity, in which motion feedback plays a significant role as an element. This role of motion feedback is particularly evident in touchscreen user interfaces that have been adopted rapidly in mobile devices. This paper presents two empirical studies performed to increase our understanding of motion feedback in terms of affective quality in mobile touchscreen user interfaces. In the first study, the relationships between three general motion properties and a selected set of affective qualities are examined. The results of this study provide a guideline for the design of motion feedback in existing mobile touchscreen user interfaces. The second study explores a new dimension of interactivity that is the Weight factor of Laban's Effort system. To experiment the Weight factor in a mobile touchscreen user interface, a pressure sensitive prototype was developed to recognize the amount of force applied by the user's finger action. With this prototype, the effects of implementing pressure requirements on four different types of user interfaces were examined. Results show that implementing the Weight factor can significantly influence the affective quality and complement the physical feel of a user interface. The issues to consider for effective implementation are also discussed.

Introduction

User experience (UX) is defined as “a person's perceptions and responses that results from the use or anticipated use of a product, system or service (ISO, 2009).” In this domain of perception and response, emotion is a primary issue as we can see from many UX frameworks (Vermeeren et al., 2008, Desmet and Hekkert, 2007). A way for a designer to approach emotion is by handling the affective quality of the artifact. Affective quality refers to the feel and impression of an artifact and is commonly described with adjectives such as simple, light, or elegant. Russell (2003) defines affective quality as the features of an artifact that influences a person's emotion. A model of product emotions by Desmet et al. (2001) shows that these features of a product evoke emotional responses through appraisal against the user's goals, standards and attitude. Positive emotions result when the features are perceived to support these concerns but negative emotions result when the features are perceived to harm them. Therefore, to achieve positive emotional experiences through an artifact, the affective quality needs to be designed with respect to the user group and usage context.

In user interfaces, interactivity is an important factor of affective quality as it relates to the feel dimension of interactive media (Svanæs, 2000). Also, a study by Lim et al. (2008) shows that interactivity has a strong influence on the user's emotional experience with an interactive product. Thus, an understanding of interactivity design is an essential part of the design for emotion. In today's user interface, a commonly used element of interactivity is motion feedback. Until the usability paradigm, the use of motion was generally reserved to serving instrumental purposes such as providing functional feedback or requesting attention (Stone et al., 2005). Nevertheless, with the development of post-WIMP generation user interfaces powered by high data processing speed and elaborate sensory hardware, motion feedback is playing a significant role in interactivity. This role extends to the influence on affective quality, as our previous work shows by verifying the significance of motion on the affective quality of user interfaces (Park and Lee, 2010). In particular, this trend is prevalent in touchscreen user interfaces which are being used increasingly in many interactive systems (Voorhees, 2008) including mobile phones (Robinson, 2006). Thus, in the UX paradigm with new generation user interfaces, motion feedback is an element that needs to be considered seriously for affective quality as an element of interactivity. However, studies on how to design interactivity in terms of affective quality are at an early stage and understanding is limited. Thus, we are motivated to gain a better understanding of motion feedback design in touchscreen user interfaces in terms of affective quality.

Our study to achieve this goal is composed of two stages. In the first stage, we examine motion properties relevant to motion feedback in mobile touchscreen user interfaces to identify their relationship with affective qualities. With the result of this examination, we can gain a more practical and detailed understanding of how to design motion feedback for affective quality. In the second stage of our study, we explore a new factor of interactivity in mobile touchscreen user interfaces to investigate a new way to design affective qualities more effectively. This new factor is the Weight factor of Laban's Effort system that refers to the force or pressure applied to the touchscreen by the user. The Weight factor of input is made to interact with motion feedback in our prototype interface and its effect on the affective quality of the user interface is examined. Overall, our investigations are performed empirically by developing prototypes and conducting user studies to extract practical design guidelines.