Comparing Physical, Overlay, and Touch Screen Parameter Controls Melanie Tory University of Victoria and Agilent Technologies 3800 Finnerty Road, Victoria, BC Canada, V8W 2Y2 mtory@cs.uvic.ca Robert Kincaid Agilent Technologies 5301 Stevens Creek Blvd Santa Clara, CA, USA 95051 robert_kincaid@agilent.com ABSTRACT We present a controlled laboratory experiment comparing touch, physical, and touch + overlay (passive finger guide) input for parameter control. Specifically we examined two target acquisition and movement tasks with dial and slider controls on horizontal touch screens. Results showed that physical controls were the fastest and required the least eye fixation time on the controls, while the overlay improved performance when compared to touch alone. Speed and accuracy differences were seen primarily for dial controls; there was little difference between input conditions for sliders. These results confirm the value of physical input devices for parameter control tasks. They also reveal that overlays can provide some of the same benefits, making them a suitable input approach for certain applications where physical controls are impractical. Author Keywords Input; touch screen; physical control; slider; dial; knob; overlay; targeting task; movement; user study; evaluation; parameter control. ACM Classification Keywords H.1.2. User/Machine Systems: Human Factors; H.5.2. User Interfaces: Input devices and strategies. INTRODUCTION Manipulating sliders and dials is a standard way to adjust continuously varying parameters in user interfaces. There are many examples of such parameters that might be used in applications for interactive surfaces. These include adjusting zoom, brightness, contrast, or RGB color levels in an imaging application, adjusting time in a video player, or adjusting filters in a map-based search tool). We focus here on parameter manipulation tasks that require precision, plus visual attention on some output that is separated from the parameter control widget. For example, for color adjustment, the user may need fine-grained control over a color slider, and will need to observe the colored object to know when to stop. What kind of input is best for this sort of task? Are touch-based dials and sliders good enough? We compare three different input devices for parameter manipulation tasks with sliders and dials on an interactive surface: touch input alone, touch plus a plastic overlay to guide the finger, and physical input devices. With physical electronics (stereos, sound mixers, oscilloscopes, etc.), people are accustomed to manipulating physical controls (dials, sliders, and buttons). Interaction with physical controls is natural and intuitive, can be done with little visual attention on the control, and can involve the whole hand. In contrast, although touch screens enable a whole new class of multitouch gesture interactions, there are still many interactions that involve single finger manipulation of sliders and dials. For adjusting non-spatial parameters, this form of interaction may be more intuitive and easier to learn than novel gestures. But how impoverished is single finger slider / dial manipulation compared to physical interfaces? What is the cost to visual attention, since the user has to look at the control? Can anything be done to bring back some of the tangibility of physical controls? With the ever-growing ubiquity of touch screen devices, it is imperative to ask these questions. The well-known benefits of physical input (e.g., graspability, minimal need for visual attention) have led to substantial interest in tangible interaction with interactive surfaces. We support and encourage further research in this area. However, tangible controls are not always ideal. Tangible interfaces typically require many physical props, which could be bulky or heavy; thus they are not very portable. Props must often be supported by a horizontal surface, making them impractical for use with mobile devices and slanted or vertical surfaces. More complex props may be expensive or complicated to build. Recently, Ullmer et al. [19] and Kincaid [11] proposed using a plastic overlay in conjunction with a touch screen, as a “guide” that contains “slotted widgets”. A clear, thin plastic overlay is affixed to the touch screen. Cut-out holes in the location of digital switches, sliders, and dials serve to guide the user’s finger and prevent it from straying outside of control areas. One application of such overlays is in portable electronic instruments such as oscilloscopes, signal generators, or sound mixers that would traditionally have physical controls, but that need a compact flat-form factor Permission to make digital or hard copies of all or part of this work for personal or classroom use is granted without fee provided that copies are not made or distributed for profit or commercial advantage and that copies bear this notice and the full citation on the first page. Copyrights for components of this work owned by others than the author(s) must be honored. Abstracting with credit is permitted. To copy otherwise, or republish, to post on servers or to redistribute to lists, requires prior specific permission and/or a fee. Request permissions from Permissions@acm.org. ITS '13, October 06 - 09 2013, St Andrews, United Kingdom Copyright is held by the owner/author(s). Publication rights licensed to ACM. ACM 978-1-4503-2271-3/13/10…$15.00. http://dx.doi.org/10.1145/2512349.2512812 Tangibles ITS'13, October 6–9, 2013, St. Andrews, UK 91