Christine J. Ziemer

Estimating Distance in Real and Virtual Environments: Does Order Make a Difference?

In this investigation, we examined how the order in which people experience real and virtual environments influences their distance estimates. Participants made two sets of distance estimates in one of the following conditions: (1) real environment first, virtual environment second; (2) virtual environment first, real environment second; (3) real environment first, real environment second; or (4) virtual environment first, virtual environment second. In Experiment 1, the participants imagined how long it would take to walk to targets in real and virtual environments. The participants’ first estimates were significantly more accurate in the real than in the virtual environment. When the second environment was the same as the first environment (real-real and virtual-virtual), the participants’ second estimates were also more accurate in the real than in the virtual environment. When the second environment differed from the first environment (real-virtual and virtual-real), however, the participants’ second estimates did not differ significantly across the two environments. A second experiment, in which the participants walked blindfolded to targets in the real environment and imagined how long it would take to walk to targets in the virtual environment, replicated these results. These subtle yet persistent order effects suggest that memory can play an important role in distance perception.

An Immersive Virtual Peer for Studying Social Influences on Child Cyclists' Road-Crossing Behavior

The goal of our work is to develop a programmatically controlled peer to bicycle with a human subject for the purpose of studying how social interactions influence road-crossing behavior. The peer is controlled through a combination of reactive controllers that determine the gross motion of the virtual bicycle, action-based controllers that animate the virtual bicyclist and generate verbal behaviors, and a keyboard interface that allows an experimenter to initiate the virtual bicyclists actions during the course of an experiment. The virtual bicyclists repertoire of behaviors includes road following, riding alongside the human rider, stopping at intersections, and crossing intersections through specified gaps in traffic. The virtual cyclist engages the human subject through gaze, gesture, and verbal interactions. We describe the structure of the behavior code and report the results of a study examining how 10- and 12-year-old children interact with a peer cyclist that makes either risky or safe choices in selecting gaps in traffic. Results of our study revealed that children who rode with a risky peer were more likely to cross intermediate-sized gaps than children who rode with a safe peer. In addition, children were significantly less likely to stop at the last six intersections after the experience of riding with the risky than the safe peer during the first six intersections. The results of the study and childrens reactions to the virtual peer indicate that our virtual peer framework is a promising platform for future behavioral studies of peer influences on childrens bicycle riding behavior.

Effects of scale change on distance perception in virtual environments

We conducted a series of experiments to investigate effects of scale changes on distance perception in virtual environments. All experiments were carried out in an HMD. Participants first made distance estimates with feedback in a virtual tunnel (adaptation) and then made distance estimates without feedback in a differently-scaled virtual environment (test). We examined several types of scale changes, including changing the size of (1) the tunnel, (2) the targets, and (3) the separation of the two targets. Changes in target size always affected distance estimates at test. When the targets became smaller, participants overshot distance and when the targets became larger, participants undershot distance. Changes in the size of the tunnel or the separation between the targets (without a change in the size of the targets) had a minimal effect on distance estimates. These results indicate that distance estimates at test were strongly influenced by familiar size cues for distance. The discussion focuses on the stability of calibration processes and mechanisms for cue integration for perceiving distance in virtual environments.

A Virtual Peer for Investigating Social Influences on Children's Bicycling

The goal of our work is to develop a programmatically controlled peer to ride with a human subject for the purpose of studying how social interactions influence riding behavior. The peer is controlled through a combination of reactive controllers that determine the gross motion of the virtual bicycle, action-based controllers that animate the virtual bicyclist and generate verbal behaviors, and a keyboard interface that allows an experimenter to initiate the virtual bicyclists actions during the course of an experiment. The virtual bicyclists repertoire of behaviors includes road following, riding alongside the human rider, stopping at intersections, and crossing intersections through specified gaps. The virtual cyclist engages the human subject through gaze, gesture, and verbal interactions. We describe the structure of the behavior code and report the results of a pilot study examining how 10- and 12-year-old children interact with a peer cyclist. Results of the pilot study showed that the presence of the peer had a significant influence on the size of the gaps taken as well as time left to spare between the participant and the trailing car in the crossed gap.

A Picture You Can Handle: Infants Treat Touch-Screen Images More Like Photographs than Objects

Infants actively explore their world in order to determine the different ways in which they can interact with various objects. Although research on infant perception has focused on how infants understand the differences between 2- and 3-dimensional objects, today’s infants increasingly encounter 2D images with interactive qualities on smart-phone screens, tablets, and laptops. The purpose of this experiment was to examine the types of manual behaviors infants direct toward tablet images and to compare these actions to those evoked by 2D photographs or 3D when tactile feedback is controlled. Infants between the ages of 7–10 months sat on their parent’s lap in front of a table with a built-in well covered by a clear, plastic sheet while the three types of displays (photographs, objects, and screen images on a tablet) were presented for 30 s each. Infants saw three examples of each type of display presented in the built-in well so that tactile feedback information from the different displays was controlled. Coders noted the proportion of trials in which infants grasped, scratched, rubbed, or patted the display. Results indicate that infants direct significantly more grasps, scratches, and rubs toward 3D objects than 2D photographs. Infants also direct more grasps to objects compared to screen images. Our data suggests that infants are treating screen images more similarly to 2D photographs than 3D objects.

Is perception-action coupling more malleable in virtual than in real environments?

Whenever we move, we gain experience with how changes in visual flow are related to movement through the environment. One way that researchers have studied these perception-action linkages is through perturbing the normal relationship between perception and action [Kunz et al. 2009; Rieser et al. 1995]. In these studies, people experience an optic flow rate that is manipulated to be significantly faster or slower than their walking rate. Comparison of distance estimates from before and after this recalibration experience typically shows that people who experience faster optic flow undershoot targets at posttest and people who experience slower optic flow overshoot targets at posttest. Here, we examined how experience with mismatched perception and action (i.e., faster or slower optic flow) in a virtual environment affects subsequent distance estimation in the same virtual environment and in a similar real environment. Of particular interest was whether perception-action coupling is more malleable in the virtual environment than in the real environment.

Optic flow and physical effort as cues for the perception of the rate of self-produced motion in VE

Understanding how humans perceive their rate of translational locomotion through the world is important for designing virtual environments. People have access to two primary classes of cues that can provide information about their movement through the environment: Visual and auditory cues (e.g. optic flow, optical expansion, Doppler shift) and somatosensory cues (e.g. effort, proprioceptive feedback.) An important research question is the relative weighting of these cues for perceiving the rate of translational movement in a virtual environment.

How does a virtual peer influence children's distance from the roadway when initiating crossing?

A bike riders distance from the roadway is one of the factors that determine the safety of the crossing. First, it dictates the vantage point from which the rider sees the oncoming traffic. Second, it governs the distance that must be crossed to clear the beam of oncoming traffic. This study investigated how the behavior of a virtual peer in an immersive bicycling simulator influences how far away from the roadway children are when they initiate crossing.

How do bicyclists intercept moving gaps in a virtual environment

Coordinating ones actions with the movements of other objects in the environments is important for both interception and avoidance tasks. Recent experiments show that performance in some interception tasks is well explained by a motion control strategy based on adjusting speed to maintain a constant bearing angle (CBA) between an individuals direction of motion and the object to be intercepted [Lenoir et al. 2002]. When the object and observer travel on intersecting, linear trajectories and the object travels with constant speed, then an observer employing the CBA strategy will move with constant speed.

Making distance judgments in real and virtual environments: does order make a difference?

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