Alexander Ng

Investigating the effects of encumbrance on one- and two- handed interactions with mobile devices

In this paper, we investigate the effects of encumbrance (carrying typical objects such as shopping bags during interaction) and walking on target acquisition on a touchscreen mobile phone. Users often hold objects and use mobile devices at the same time and we examined the impact encumbrance has on one- and two- handed interactions. Three common input postures were evaluated: two-handed index finger, one-handed preferred thumb and two-handed both thumbs, to assess the effects on performance of carrying a bag in each hand while walking. The results showed a significant decrease in targeting performance when users were encumbered. For example, input accuracy dropped to 48.1% for targeting with the index finger when encumbered, while targeting error using the preferred thumb to input was 4.2mm, an increase of 40% compared to unencumbered input. We also introduce a new method to evaluate the users preferred walking speed when interacting - PWS&I, and suggest future studies should use this to get a more accurate measure of the users input performance.

The Impact of Encumbrance on Mobile Interactions

This paper investigates the effects of encumbrance (holding different types of objects while using mobile devices) to understand the interaction difficulties that it causes. An experiment was conducted where participants performed a target acquisition task on a touchscreen mobile phone while carrying different types of bags and boxes. Mobility was also evaluated since people carry items from one place to another. Motion capture hardware was used to track hand and arm postures to examine how holding the different types of objects caused excessive movement and instability therefore resulting in performance to decline. The results showed encumbrance and mobility caused target accuracy to decrease although input while holding the box under the non-dominant arm was more accurate and exerted quicker targeting times than holding no objects. Encumbrance affected the dominant hand more than the non-dominant hand as targeting error significantly increased and caused greater hand instability. The issues caused by encumbrance suggest the topic requires more attention from researchers and users would benefit greatly if better interaction techniques and applications are developed to counteract the problems.

I Am The Passenger: How Visual Motion Cues Can Influence Sickness For In-Car VR

This paper explores the use of VR Head Mounted Displays (HMDs) in-car and in-motion for the first time. Immersive HMDs are becoming everyday consumer items and, as they offer new possibilities for entertainment and productivity, people will want to use them during travel in, for example, autonomous cars. However, their use is confounded by motion sickness caused in-part by the restricted visual perception of motion conflicting with physically perceived vehicle motion (accelerations/rotations detected by the vestibular system). Whilst VR HMDs restrict visual perception of motion, they could also render it virtually, potentially alleviating sensory conflict. To study this problem, we conducted the first on-road and in motion study to systematically investigate the effects of various visual presentations of the real-world motion of a car on the sickness and immersion of VR HMD wearing passengers. We established new baselines for VR in-car motion sickness, and found that there is no one best presentation with respect to balancing sickness and immersion. Instead, user preferences suggest different solutions are required for differently susceptible users to provide usable VR in-car. This work provides formative insights for VR designers and an entry point for further research into enabling use of VR HMDs, and the rich experiences they offer, when travelling.

Comparing evaluation methods for encumbrance and walking on interaction with touchscreen mobile devices

In this paper, two walking evaluation methods were compared to evaluate the effects of encumbrance while the preferred walking speed (PWS) is controlled. Users frequently carry cumbersome objects (e.g. shopping bags) and use mobile devices at the same time which can cause interaction difficulties and erroneous input. The two methods used to control the PWS were: walking on a treadmill and walking around a predefined route on the ground while following a pacesetter. The results from our target acquisition experiment showed that for ground walking at 100% of PWS, accuracy dropped to 36% when carrying a bag in the dominant hand while accuracy reduced to 34% for holding a box under the dominant arm. We also discuss the advantages and limitations of each evaluation method when examining encumbrance and suggest treadmill walking is not the most suitable approach to use if walking speed is an important factor in future mobile studies.

Evaluating Haptic Feedback on a Steering Wheel in a Simulated Driving Scenario

This paper investigates how perceivable haptic feedback patterns are using an actuated surface on a steering wheel. Six solenoids were embedded along the surface of the wheel, creating three bumps under each palm. The solenoids can be used to create a range of different tactile patterns. As a result of the design recommendation by Gallace et al. [Gallace2006a] maximally four of the six solenoids were actuated simultaneously, resulting in 57 patterns to test. A simulated driving study was conducted to investigate (1) the optimal number of actuated solenoids and (2) the most perceivable haptic patterns. A relationship between number of actuated solenoids and pattern identification rate was established. Perception accuracy drops above three active solenoids. Haptic patterns mirrored symmetrically on both hands were perceived more accurately. Practical applications for displaying tactile messages on the steering wheel are e.g. dead angles, upcoming road conditions, navigation information (i.e. conveying information discretely to the driver).

The effects of encumbrance on mobile interactions

The popularity of touchscreen mobile devices gives users a variety of useful apps and functionality on the move. As a result, mobile devices are being used in a range of different contexts. One common scenario that has received little attention from researchers is the effects of encumbrance carrying objects (for example, shopping bags and personal gear) and interacting with mobile devices at the same time. This is a frequent everyday situation and one that can cause interaction difficulties [3]. There is a lack of knowledge of the impact encumbrance has on interaction therefore the usability issues in these physically and mentally demanding contexts are unknown. Prior to the start of our research, there was only one related study that has examined input performance with handheld devices while multitasking with different types of objects [7]. A better understanding of the interaction problems caused by encumbrance would allow researchers to develop more effective input techniques on touchscreen mobile devices.

Investigating Pressure Input and Haptic Feedback for In-Car Touchscreens and Touch Surfaces

The way drivers interact with in-car centre console controls is undergoing radical change as physical switchgear are replaced by virtual counterparts with the use of touchscreens. This provides the opportunity to design new input techniques to improve the way on-screen widgets are operated in driving situations. This paper investigates the effectiveness of pressure-based input with haptic feedback as an alternative touch modality for in-car interactions. Two user studies were conducted: one using a driving simulator and the other inside a vehicle driven on public roads, to evaluate two main pressure-based input techniques: positional and rate-based control. The results from a list-based targeting task showed that rate-based control performed well and was comparable to standard touch input and the physical dial while users had difficulties with positional pressure input. These findings from our studies will help engineers make more appropriate design decisions when developing in-car interactions with touchscreens and touch surfaces.

The relationship between encumbrance and walking speed on mobile interactions

The effects of encumbrance (holding cumbersome objects while using mobile devices) have received little attention when examining mobile interactions. People often carry items while on the move and use their mobile devices at the same time, causing interaction problems. The study presented is part of an on-going project examining the relationship between encumbrance and walking speed and the impact the relationship has on targeting performance on a touchscreen mobile phone. We also compare two evaluation techniques used in mobile studies: 1)walking on a treadmill and 2)walking on the ground and found a drop in preferred walking speed (PWS) of 27% on the treadmill. The results show that when users walked on the ground at a fixed PWS, targeting error increased as much as 112% compared to standing still when holding a bag in the dominant hand.

An Evaluation of Input Controls for In-Car Interactions

The way drivers operate in-car systems is rapidly changing as traditional physical controls, such as buttons and dials, are being replaced by touchscreens and touch-sensing surfaces. This has the potential to increase driver distraction and error as controls may be harder to find and use. This paper presents an in-car, on the road driving study which examined three key types of input controls to investigate their effects: a physical dial, pressure-based input on a touch surface and touch input on a touchscreen. The physical dial and pressure-based input were also evaluated with and without haptic feedback. The study was conducted with users performing a list-based targeting task using the different controls while driving on public roads. Eye-gaze was recorded to measure distraction from the primary task of driving. The results showed that target accuracy was high across all input methods (greater than 94%). Pressure-based targeting was the slowest while directly tapping on the targets was the faster selection method. Pressure-based input also caused the largest number of glances towards to the touchscreen but the duration of each glance was shorter than directly touching the screen. Our study will enable designers to make more appropriate design choices for future in-car interactions.

Evaluation of Haptic Patterns on a Steering Wheel

Infotainment Systems can increase mental workload and divert visual attention away from looking ahead on the roads. When these systems give information to the driver, providing it through the tactile channel on the steering wheel might improve driving behaviour and safety. This paper describes an investigation into the perceivability of haptic feedback patterns using an actuated surface on a steering wheel. Six solenoids were embedded along the rim creating three bumps under each palm. A simulated driving study was conducted to test for recognition accuracy of the haptic patterns (81.3%). There was no significant increase in lane deviation or steering angle during haptic pattern presentation. These results suggest that drivers can reliably distinguish between cutaneous patterns presented on the steering wheel. Our findings can assist in delivering non-critical messages to the driver (e.g. driving performance, incoming text messages, etc.) without decreasing driving performance or increasing perceived mental workload.