Jens R. Helmert

The perception of egocentric distances in virtual environments - A review

Over the last 20 years research has been done on the question of how egocentric distances, i.e., the subjectively reported distance from a human observer to an object, are perceived in virtual environments. This review surveys the existing literature on empirical user studies on this topic. In summary, there is a mean estimation of egocentric distances in virtual environments of about 74% of the modeled distances. Many factors possibly influencing distance estimates were reported in the literature. We arranged these factors into four groups, namely measurement methods, technical factors, compositional factors, and human factors. The research on these factors is summarized, conclusions are drawn, and promising areas for future research are outlined.

The effects of self-involvement on attention, arousal, and facial expression during social interaction with virtual others: A psychophysiological study

Abstract Social neuroscience has shed light on the underpinnings of understanding other minds. The current study investigated the effect of self-involvement during social interaction on attention, arousal, and facial expression. Specifically, we sought to disentangle the effect of being personally addressed from the effect of decoding the meaning of another persons facial expression. To this end, eye movements, pupil size, and facial electromyographic (EMG) activity were recorded while participants observed virtual characters gazing at them or looking at someone else. In dynamic animations, the virtual characters then displayed either socially relevant facial expressions (similar to those used in everyday life situations to establish interpersonal contact) or arbitrary facial movements. The results show that attention allocation, as assessed by eye-tracking measurements, was specifically related to self-involvement regardless of the social meaning being conveyed. Arousal, as measured by pupil size, was primarily related to perceiving the virtual characters gender. In contrast, facial EMG activity was determined by the perception of socially relevant facial expressions irrespective of whom these were directed towards.

Change detection and occlusion modes in road-traffic scenarios

Abstract Change blindness phenomena are widely known in cognitive science, but their relation to driving is not quite clear. We report a study where subjects viewed colour video stills of natural traffic while eye movements were recorded. A change could occur randomly in three different occlusion modes—blinks, blanks and saccades—or during a fixation (as control condition). These changes could be either relevant or irrelevant with respect to the traffic safety. We used deletions as well as insertions of objects. All occlusion modes were equivalent concerning detection rate and reaction time, deviating from the control condition only. The detection of relevant changes was both more likely and faster than that of irrelevant ones, particularly for relevant insertions, which approached the base line level. Even in this case, it took about 180 ms longer to react to changes when they occurred during a saccade, blink or blank. In a second study, relevant insertions and the blank occlusion were used in a driving simulator environment. We found a surprising effect in the dynamic setting: an advantage in change detection rate and time with blanks compared to the control condition. Change detection was also good during blinks, but not in saccades. Possible explanation of these effects and their practical implications are discussed.

Towards attention-centered interfaces: An aesthetic evaluation of perspective with eye tracking

The established method of representing three-dimensional space on a two-dimensional surface involves camera based, point of regard systems, comparable in design to the early “camera obscura”. However, geometrical limitations of such models lead to distortions of perspective when projected. This research investigated the influence of single- versus multi-perspectives on aesthetic choices within one image. A clear perceptual bias towards multi-perspective images was found, additionally supported by an eye tracking study. We propose that human users are more attracted by multi-perspective images, which emphasise the “semantic foci” of the scene, than by those being synthesized statically with only one geometrical prospect.

Gaze transfer in remote cooperation: Is it always helpful to see what your partner is attending to?

Establishing common ground in remote cooperation is challenging because nonverbal means of ambiguity resolution are limited. In such settings, information about a partners gaze can support cooperative performance, but it is not yet clear whether and to what extent the abundance of information reflected in gaze comes at a cost. Specifically, in tasks that mainly rely on spatial referencing, gaze transfer might be distracting and leave the partner uncertain about the meaning of the gaze cursor. To examine this question, we let pairs of participants perform a joint puzzle task. One partner knew the solution and instructed the other partners actions by (1) gaze, (2) speech, (3) gaze and speech, or (4) mouse and speech. Based on these instructions, the acting partner moved the pieces under conditions of high or low autonomy. Performance was better when using either gaze or mouse transfer compared to speech alone. However, in contrast to the mouse, gaze transfer induced uncertainty, evidenced in delayed responses to the cursor. Also, participants tried to resolve ambiguities by engaging in more verbal effort, formulating more explicit object descriptions and fewer deictic references. Thus, gaze transfer seems to increase uncertainty and ambiguity, thereby complicating grounding in this spatial referencing task. The results highlight the importance of closely examining task characteristics when considering gaze transfer as a means of support.

Comparing two types of engineering visualizations: Task-related manipulations matter

This study focuses on the comparison of traditional engineering drawings with a CAD (computer aided design) visualization in terms of user performance and eye movements in an applied context. Twenty-five students of mechanical engineering completed search tasks for measures in two distinct depictions of a car engine component (engineering drawing vs. CAD model). Besides spatial dimensionality, the display types most notably differed in terms of information layout, access and interaction options. The CAD visualization yielded better performance, if users directly manipulated the object, but was inferior, if employed in a conventional static manner, i.e. inspecting only predefined views. An additional eye movement analysis revealed longer fixation durations and a stronger increase of task-relevant fixations over time when interacting with the CAD visualization. This suggests a more focused extraction and filtering of information. We conclude that the three-dimensional CAD visualization can be advantageous if its ability to manipulate is used.

Implicit food associations as obstacles to healthy nutrition: the need for further research:

Healthy nutrition is the driving force behind measures to address the obesity and diabetes epidemic. Therefore, the relevance of healthy nutrition to public health is steadily increasing. Although many consumers have positive attitudes towards healthy nutrition, their eating habits do not always match these attitudes. This paper suggests that individuals can overcome the discrepancy between attitude/intention and behaviour if they consider implicit associations with healthy or unhealthy nutrition. Our paper aims to develop a research strategy to analyse the impact of the interplay between explicit and implicit food associations on food consumption. The suggested process comprises the following steps: consumer segmentation, isolated analysis of different implicit drivers, holistic examination of interaction effects of different drivers and development of implications for policy makers and managers. Br J Diabetes Vasc Dis 2011;11:182-186

I see you remembering: what eye movements can reveal about process characteristics of prospective memory.

Prospective memory performance describes the delayed execution of an intended action. As this requires a mixture of memory and attentional control functions, current research aims at delineating the specific processes associated with solving a prospective memory task. Therefore, the current study measured, analysed and compared eye movements of participants who performed a prospective memory, a free viewing, and a visual search task. By keeping constant the prospective memory cue as well as the context of tasks, we aimed at putting the processes of solving prospective memory tasks into context. The results show, that when a prospective memory task is missed, the continuous gaze behaviour is rather similar to the gaze behaviour during free viewing. When the prospective memory task is successfully solved, on the other hand, average gaze behaviour is between free viewing and visual search. Furthermore, individual differences in eye movements were found between low and high performers. Our data suggest that a prospective memory task can be solved in different ways, therefore different processes can be observed.

Commonalities and Differences in Eye Movement Behavior When Exploring Aerial and Terrestrial Scenes

Eye movements can provide fast and precise insights into ongoing mechanisms of attention and information processing. In free exploration of natural scenes, it has repeatedly been shown that fixation durations increase over time, while saccade amplitudes decrease. This gaze behavior has been explained as a shift from ambient (global) to focal (local) processing as a means to efficiently understand different environments. In the current study, we analyzed eye movement behavior during the inspection of terrestrial and aerial views of real-world scene images. Our results show that the ambient to focal strategy is preserved across both perspectives. However, there are several perspective-related differences: For aerial views, the first fixation duration is prolonged, showing immediate processing difficulties. Furthermore, fixation durations and saccade amplitudes are longer throughout the overall time of scene exploration, showing continued difficulties that affect both processing of information and image scanning strategies. The temporal and spatial scanning of aerial views is also less similar between observers than for terrestrial scenes, suggesting an inability to use normal scanning patterns. The observed differences in eye movement behavior when inspecting terrestrial and aerial views suggest an increased processing effort for visual information that deviates from our everyday experiences.

Limitations of gaze transfer: Without visual context, eye movements do not to help to coordinate joint action, whereas mouse movements do

Remote cooperation can be improved by transferring the gaze of one participant to the other. However, based on a partners gaze, an interpretation of his communicative intention can be difficult. Thus, gaze transfer has been inferior to mouse transfer in remote spatial referencing tasks where locations had to be pointed out explicitly. Given that eye movements serve as an indicator of visual attention, it remains to be investigated whether gaze and mouse transfer differentially affect the coordination of joint action when the situation demands an understanding of the partners search strategies. In the present study, a gaze or mouse cursor was transferred from a searcher to an assistant in a hierarchical decision task. The assistant could use this cursor to guide his movement of a window which continuously opened up the display parts the searcher needed to find the right solution. In this context, we investigated how the ease of using gaze transfer depended on whether a link could be established between the partners eye movements and the objects he was looking at. Therefore, in addition to the searchers cursor, the assistant either saw the positions of these objects or only a grey background. When the objects were visible, performance and the number of spoken words were similar for gaze and mouse transfer. However, without them, gaze transfer resulted in longer solution times and more verbal effort as participants relied more strongly on speech to coordinate the window movement. Moreover, an analysis of the spatio-temporal coupling of the transmitted cursor and the window indicated that when no visual object information was available, assistants confidently followed the searchers mouse but not his gaze cursor. Once again, the results highlight the importance of carefully considering task characteristics when applying gaze transfer in remote cooperation.