Hans-Joachim Bieg

Eye and pointer coordination in search and selection tasks

Selecting a graphical item by pointing with a computer mouse is a ubiquitous task in many graphical user interfaces. Several techniques have been suggested to facilitate this task, for instance, by reducing the required movement distance. Here we measure the natural coordination of eye and mouse pointer control across several search and selection tasks. We find that users automatically minimize the distance to likely targets in an intelligent, task dependent way. When target location is highly predictable, top-down knowledge can enable users to initiate pointer movements prior to target fixation. These findings question the utility of existing assistive pointing techniques and suggest that alternative approaches might be more effective.

Looking for Discriminating Is Different from Looking for Looking's Sake

Recent studies provide evidence for task-specific influences on saccadic eye movements. For instance, saccades exhibit higher peak velocity when the task requires coordinating eye and hand movements. The current study shows that the need to process task-relevant visual information at the saccade endpoint can be, in itself, sufficient to cause such effects. In this study, participants performed a visual discrimination task which required a saccade for successful completion. We compared the characteristics of these task-related saccades to those of classical target-elicited saccades, which required participants to fixate a visual target without performing a discrimination task. The results show that task-related saccades are faster and initiated earlier than target-elicited saccades. Differences between both saccade types are also noted in their saccade reaction time distributions and their main sequences, i.e., the relationship between saccade velocity, duration, and amplitude.

Gaze-Assisted Pointing for Wall-Sized Displays

Previous studies have argued for the use of gaze-assisted pointing techniques (MAGIC) in improving human-computer interaction. Here, we present experimental findings that were drawn from human performance of two tasks on a wall-sized display. Our results show that a crude adoption of MAGIC across a range of complex tasks does not increase pointing performance. More importantly, a detailed analysis of user behavior revealed several issues that were previously ignored (such as, interference of corrective saccades, increased decision time due to variability of precision, errors due to eye-hand asynchrony, and interference with search behavior) which should influence the development of gaze-assisted technology.

Asymmetric saccade reaction times to smooth pursuit

Before initiating a saccade to a moving target, the brain must take into account the target’s eccentricity as well as its movement direction and speed. We tested how the kinematic characteristics of the target influence the time course of this oculomotor response. Participants performed a step-ramp task in which the target object stepped from a central to an eccentric position and moved at constant velocity either to the fixation position (foveopetal) or further to the periphery (foveofugal). The step size and target speed were varied. Of particular interest were trials that exhibited an initial saccade prior to a smooth pursuit eye movement. Measured saccade reaction times were longer in the foveopetal than in the foveofugal condition. In the foveopetal (but not the foveofugal) condition, the occurrence of an initial saccade, its reaction time as well as the strength of the pre-saccadic pursuit response depended on both the target’s speed and the step size. A common explanation for these results may be found in the neural mechanisms that select between oculomotor response alternatives, i.e., a saccadic or smooth response.

Saccade reaction time asymmetries during task-switching in pursuit tracking

We investigate how smooth pursuit eye movements affect the latencies of task-switching saccades. Participants had to alternate their foveal vision between a continuous pursuit task in the display center and a discrete object discrimination task in the periphery. The pursuit task was either carried out by following the target with the eyes only (ocular) or by steering an on-screen cursor with a joystick (oculomanual). We measured participants’ saccadic reaction times (SRTs) when foveal vision was shifted from the pursuit task to the discrimination task and back to the pursuit task. Our results show asymmetries in SRTs depending on the movement direction of the pursuit target: SRTs were generally shorter in the direction of pursuit. Specifically, SRTs from the pursuit target were shorter when the discrimination object appeared in the motion direction. SRTs to pursuit were shorter when the pursuit target moved away from the current fixation location. This result was independent of the type of smooth pursuit behavior that was performed by participants (ocular/oculomanual). The effects are discussed in regard to asymmetries in attention and processes that suppress saccades at the onset of pursuit.

Measuring unrestrained gaze on wall-sized displays

Motivation -- Natural gaze involves the coordinated movements of eye, head and torso. This allows access to a wide field of view, up to a range of 260° (Chen, Solinger, Poncet & Lancet, 1999). The recent increase in large displays places a demand on being able to track a mobile users gaze over this extensive range. Research approach -- We developed an extensible system for measuring the gaze of users on wall-sized displays. Our solution combines the inputs of a conventional head-mounted eyetracker (Eyelink2©, SR Research) and motion-capture system (Vicon MX©, Vicon), to provide real-time measurements of a mobile users gaze in 3D space. Findings/Design -- The presented system serves as a single platform for studying user behavior across a wide range of tasks: single-step saccade shifts, free-viewing of natural scenes, visual search and gaze-assisted user interfaces. Importantly, it allows eye- and head-movements to be separately measured without compromising the accuracy of combined gaze measurements. Take away message -- Unrestrained gaze movements on a large display can be accurately measured by suitably combining the inputs of conventional eye- and body-tracking hardware.

Attentional biases during steering behavior

In the current study, we examine eye movements of human operators during a combined steering and discrimination task. In this task, observers had to alternate their gaze between a central steering task and a discrimination task in the periphery. Our results show that the observers gaze behavior is influenced by the motion direction of the steering task. Saccade reaction times (SRTs) of saccades to the discrimination target were shorter if the target appeared in the steering direction. SRTs back to the steering task were shorter when the steering target moved away from the discrimination target. These effects are likely the result of motion-related attention shifts and an interaction of the saccadic and smooth pursuit eye movement system.

Einfluss von Ablenkung und Augenbewegungen auf Steuerungsaufgaben

In der vorliegenden Studie wurde der Einfluss visueller Ablenkung auf Steuerungsaufgaben untersucht. Die Ergebnisse deuten darauf hin, dass bereits eine kurze Verlagerung der Aufmerksamkeit und des Blicks mit einer systematischen Beeinflussung der Steuerungsaufgabe einhergeht. Im Gegenzug findet auch eine systematische Beeinflussung der Augenbewegungen durch die gleichzeitig durchgeführte Steuerungsaufgabe statt. Die Berücksichtigung solcher Interferenzen kann bei der Entwicklung von grafischen On-Board-Informationssystemen für Fahroder Flugzeuge von Nutzen sein.

Enhancing input device evaluation: longitudinal approaches

In this paper we present our experiences with longitudinal study designs for input device evaluation. In this domain, analyzing learning is currently the main reason for applying longitudinal designs. We will shortly discuss related research questions and outline two case studies in which we used different approaches to address this issue. Finally, we will point out future research tasks in the context of longitudinal evaluation methods.