Benjamin Chihak

Perceiving and acting on complex affordances: how children and adults bicycle across two lanes of opposing traffic

This investigation examined how children and adults negotiate a challenging perceptual-motor problem with significant real-world implications--bicycling across two lanes of opposing traffic. Twelve- and 14-year-olds and adults rode a bicycling simulator through an immersive virtual environment. Participants crossed intersections with continuous cross traffic coming from opposing directions. Opportunities for crossing were divided into aligned (far gap opens with or before near gap) and rolling (far gap opens after near gap) gap pairs. Children and adults preferred rolling to aligned gap pairs, though this preference was stronger for adults than for children. Crossing aligned versus rolling gap pairs produced substantial differences in direction of travel, speed of crossing, and timing of entry into the near and far lanes. For both aligned and rolling gap pairs, children demonstrated less skill than adults in coordinating self and object movement. These findings have implications for understanding perception-action-cognition links and for understanding risk factors underlying car-bicycle collisions.

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.

How Children and Adults Learn to Intercept Moving Gaps

We used an immersive virtual environment to examine how children and adults learn to intercept moving gaps and whether children and adults benefit from variability of practice. Children (10- and 12-year-olds) and adults attempted to bicycle between two moving vehicle-size blocks without stopping. In Experiment 1, block motions were timed such that if participants maintained a constant speed, they would intercept the gap between the blocks. By the last set of intersections, adults learned to maintain a constant speed throughout the approach to the intersection, 12-year-olds exhibited less variability in time-to-spare when they intercepted the blocks, and 10-year-olds exhibited no significant change across intersection sets. In Experiment 2, block motions during the first eight intersections were timed such that participants needed to either speed up or slow down on all intersections or needed to speed up on half and slow down on half of the intersections. On the last four intersections, all age groups encountered a novel block timing in which no adjustment in speed was necessary to intercept the blocks. The adults performed well regardless of whether they experienced consistent or variable block timings. The 10-year-olds in the variable condition performed better on slow-down trials than their peers in the slow-down condition but performed worse on speed-up trials than their peers in the speed-up condition. Discussion focuses on possible developmental changes in reliance on perceptually available and remembered information in complex perception-action tasks.

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.

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.