03-01-2013, 09:50 AM
Negative Feedback for Small Capacitive Touchscreen Interfaces
[attachment=46259]
Abstract:
Touchscreen technology has become pervasive in the consumer product arena over the last decade, offering some distinct advantages such as software reconfigurable interfaces and the removal of space consuming mice and keyboards.However, there are significant drawbacks to these devices that have limited their adoption by some users. Most notably, standard touchscreens demand the user’s visual attention and require them to look at the input device to avoid pressing the wrong button. This issue is particularly important for mobile, capacitive sensing, non-stylus devices, such as the iPhone where small button sizes can generate high error rates. While previous work has shown the benefits of augmenting such interfaces with audio or vibrotactile feedback, only positive feedback (confirmation of button presses) has been considered. In this paper we present a simple prototype interface that provides negative vibrotactile feedback. By negative, we mean feedback is generated when an inactive or ambiguous part of the screen, such as the area between two buttons, is touched. First, we present a usability study comparing positive and negative vibrotactile feedback for a benchmark numerical data entry task. The difference in performance is not statistically significant, implying negative feedback provides comparable benefits. Next, based on the experimenter’s observations and the user’s comments, we introduce a multi-modal feedback strategy – combining complementary positive audio and negative vibrotactile signals. User tests on a text entry experiment show that, with multimodal feedback, users exhibit a (statistically significant) 24% reduction in corrective key presses, as compared to positive audio feedback alone. Exit survey comments indicate that users favour multi-modal feedback.
INTRODUCTION
In recent years, touch screen technology has progressed rapidly and has increased in popularity with developers and consumers alike. Touchscreen devices, in the forms of shopping kiosks, ATMs, tablet PCs, and smart phones, are now prevalent in everyday life. They offer several advantages.First, a single touch screen can replace an LCD display, a conventional keyboard, and a mouse or joystick; drastically reducing the physical footprint of the user console. Second, for novice users they are more intuitive because touch interfaces can be configured to provide a one-to-one correspondence between the available input options and the user input device – eliminating the extra unused buttons seen on some keypad interfaces or the need to use awkward button combinations (e.g. control-alt-delete). Finally these interfaces are software reconfigurable, enabling the programmer to present the user with a custom designed layout suited to each phase of the task.
Conversely, the problems associated with touch screen use are also becoming more apparent as they are used for a greater variety of tasks. First among these is the lack of intrinsic haptic feedback. Rapid touch typing on a traditional keyboard is facilitated by the contoured button surface and mechanical resistance of the keys. In contrast, non-augmented touchscreen buttons demand constant visual attention to avoid pressing the wrong button. A second issue is that the display and input device are typically collocated, which may not be ergonomic for extended use.
The relative weighting of the pros and cons is specific to both the user and the task. For example, the advantages of touchscreens seem to outweigh the disadvantages for novice users, whom will likely prefer a more intuitive, task customized interface. Similarly, the touchscreen’s ergonomic drawbacks will likely go unnoticed for tasks which have brief durations or require very few interactions with the touchscreen.
In this paper we focus on improving touchscreen experiences for experienced users executing demanding tasks.We define the experienced user as someone who expects to perform the task frequently for extended periods. As such, they are willing to tradeoff “easy to learn” for performance, similar to touch typists [1]. We define a demanding task as one that: (1) requires users to divert visual attention away from the input device for performance monitoring; and, (2) requires a high number of interface interactions per unit time.In this work, we explore the idea of negative vibrotactile feedback for small, capacitive touchscreen interfaces.By “negative”, we mean that the interface should provide feedback when the user does something potentially erroneous or ambiguous. We hypothesize that, for the experienced user performing demanding tasks, this type of feedback can improve performance, while being less irritating than a constant stream of positive feedback. Section2 reviews related work on touchscreens and vibrotactile feedback, and explicitly states the research questions addressed in this study. Sections 3 - 4 describe a controlled usability study performed to (in)validate these hypotheses and discuss lessons learned.
Section 5 takes the lessons learned from the initial study and presents a new design consisting of a small,capacitive touchscreen interface that combines negative and positive feedback. Section 6 discusses the results of the second usability study and compares the new feedback mode with the mode presently available on a popular consumer product (Apple’s iPhone). Concluding remarks and the relationship of these findings to existing knowledge are presented in Section 7.
[attachment=46259]
Abstract:
Touchscreen technology has become pervasive in the consumer product arena over the last decade, offering some distinct advantages such as software reconfigurable interfaces and the removal of space consuming mice and keyboards.However, there are significant drawbacks to these devices that have limited their adoption by some users. Most notably, standard touchscreens demand the user’s visual attention and require them to look at the input device to avoid pressing the wrong button. This issue is particularly important for mobile, capacitive sensing, non-stylus devices, such as the iPhone where small button sizes can generate high error rates. While previous work has shown the benefits of augmenting such interfaces with audio or vibrotactile feedback, only positive feedback (confirmation of button presses) has been considered. In this paper we present a simple prototype interface that provides negative vibrotactile feedback. By negative, we mean feedback is generated when an inactive or ambiguous part of the screen, such as the area between two buttons, is touched. First, we present a usability study comparing positive and negative vibrotactile feedback for a benchmark numerical data entry task. The difference in performance is not statistically significant, implying negative feedback provides comparable benefits. Next, based on the experimenter’s observations and the user’s comments, we introduce a multi-modal feedback strategy – combining complementary positive audio and negative vibrotactile signals. User tests on a text entry experiment show that, with multimodal feedback, users exhibit a (statistically significant) 24% reduction in corrective key presses, as compared to positive audio feedback alone. Exit survey comments indicate that users favour multi-modal feedback.
INTRODUCTION
In recent years, touch screen technology has progressed rapidly and has increased in popularity with developers and consumers alike. Touchscreen devices, in the forms of shopping kiosks, ATMs, tablet PCs, and smart phones, are now prevalent in everyday life. They offer several advantages.First, a single touch screen can replace an LCD display, a conventional keyboard, and a mouse or joystick; drastically reducing the physical footprint of the user console. Second, for novice users they are more intuitive because touch interfaces can be configured to provide a one-to-one correspondence between the available input options and the user input device – eliminating the extra unused buttons seen on some keypad interfaces or the need to use awkward button combinations (e.g. control-alt-delete). Finally these interfaces are software reconfigurable, enabling the programmer to present the user with a custom designed layout suited to each phase of the task.
Conversely, the problems associated with touch screen use are also becoming more apparent as they are used for a greater variety of tasks. First among these is the lack of intrinsic haptic feedback. Rapid touch typing on a traditional keyboard is facilitated by the contoured button surface and mechanical resistance of the keys. In contrast, non-augmented touchscreen buttons demand constant visual attention to avoid pressing the wrong button. A second issue is that the display and input device are typically collocated, which may not be ergonomic for extended use.
The relative weighting of the pros and cons is specific to both the user and the task. For example, the advantages of touchscreens seem to outweigh the disadvantages for novice users, whom will likely prefer a more intuitive, task customized interface. Similarly, the touchscreen’s ergonomic drawbacks will likely go unnoticed for tasks which have brief durations or require very few interactions with the touchscreen.
In this paper we focus on improving touchscreen experiences for experienced users executing demanding tasks.We define the experienced user as someone who expects to perform the task frequently for extended periods. As such, they are willing to tradeoff “easy to learn” for performance, similar to touch typists [1]. We define a demanding task as one that: (1) requires users to divert visual attention away from the input device for performance monitoring; and, (2) requires a high number of interface interactions per unit time.In this work, we explore the idea of negative vibrotactile feedback for small, capacitive touchscreen interfaces.By “negative”, we mean that the interface should provide feedback when the user does something potentially erroneous or ambiguous. We hypothesize that, for the experienced user performing demanding tasks, this type of feedback can improve performance, while being less irritating than a constant stream of positive feedback. Section2 reviews related work on touchscreens and vibrotactile feedback, and explicitly states the research questions addressed in this study. Sections 3 - 4 describe a controlled usability study performed to (in)validate these hypotheses and discuss lessons learned.
Section 5 takes the lessons learned from the initial study and presents a new design consisting of a small,capacitive touchscreen interface that combines negative and positive feedback. Section 6 discusses the results of the second usability study and compares the new feedback mode with the mode presently available on a popular consumer product (Apple’s iPhone). Concluding remarks and the relationship of these findings to existing knowledge are presented in Section 7.