Biomedical subjects

Ranxiao Frances Wang

Publications and source records attributed to Ranxiao Frances Wang.

11 recordsLinked to original sources

PubMed2006

Spatial updating relies on an egocentric representation of space: effects of the number of objects.

Models of spatial updating attempt to explain how representations of spatial relationships between the actor and objects in the environment change as the actor moves. In allocentric models, object locations are encoded in an external reference frame, and only the actor's position and orientation in that reference frame need to be updated. Thus, spatial updating should be independent of the number of objects in the environment (set size). In egocentric updating models, object locations are encoded relative to the actor, so the location of each object relative to the actor must be updated as the actor moves. Thus, spatial updating efficiency should depend on set size. We examined which model better accounts for human spatial updating by having people reconstruct the locations of varying numbers of virtual objects either from the original study position or from a changed viewing position. In consistency with the egocentric updating model, object localization following a viewpoint change was affected by the number of objects in the environment.

Environment↗

PubMed2004

Action, verbal response and spatial reasoning.

Studies have shown that perception of distance, orientation and size can be dissociated from action tasks. The action system seems to possess more veridical, unbiased information than the perceptual/verbal system. The current study examines the nature of the distinction between action and verbal responses in a spatial reasoning task. Participants imagined themselves facing different orientations and either pointed to where other objects would be, or verbally reported their egocentric directions (e.g., "50 degrees to my left"). When using pointing responses, RT and error increased as a function of the angular disparity between the imagined heading and their actual heading. However, when using verbal responses, performance was not affected by angular disparity, suggesting that participants knew the direction of the targets from the imagined perspective but could not point to them directly. The verbal and action systems have fundamentally different information or processes rather than quantitatively different ones.

Decision Making↗

PubMed2004

Between reality and imagination: when is spatial updating automatic?

Spatial updating has been shown to occur automatically and operate on both real and imagined environments. In three experiments, we compared spatial updating in real and imagined environments and examined when automatic spatial updating occurs. Participants learned the locations of real objects in a room and imagined being in their kitchens. They turned to face either the kitchen or the room targets and pointed to the targets before and after turning. Although objects in the real environment were automatically updated when the participants turned in the imagined environment, targets in the imagined environment were not automatically updated when the participants turned in the real environment. However, explicit spatial updating of imagined environments was as efficient as that of real environments. Automatic updating of the real objects required perceptual experience of these targets, either visually or by touch, and did not occur when the targets were described verbally. Implications for spatial cognition research are discussed.

Adolescent↗

PubMed2003

Changing perspective within and across environments.

Perspective change within a single environment is a slow and effortful process. However, little research has addressed perspective change across multiple environments. Using a task-set switching paradigm, subjects judged spatial relationships between target locations from differing perspectives. Response times were longer when successive trials probed different perspectives. However, this cost was greater when perspective was changed within a single environment compared to when it was changed across two environments. This result indicates that the processing of perspective change, and perhaps general spatial reasoning, differs in these two cases. Implications for theories of perspective change and environmental knowledge are discussed.

Cues↗

PubMed2003

Human navigation in nested environments.

Navigation in humans and many other animals relies on spatial representations of their environments. Three experiments examined how humans maintain sense of orientation between nested environments. Subjects can acquire new spatial representations easily without integrating them into their existing spatial knowledge system. While navigating between nested environments, subjects seemed to constantly switch between the currently processed environment by reorienting to approaching environments and losing track of old environments at given spatial regions. These results suggest that spatial updating in naturalistic, nested environments does not occur for all environments at the same time. Implications for the hierarchical theory of spatial representations and the path integration theory of navigation are discussed.

Environment↗

PubMed2003

The locus of spatial attention during the temporal integration of visual memories and visual percepts.

Temporal integration is a process by which two serially presented visual stimuli are mentally integrated to form a composite representation. In the present research, we explored how spatial selective attention is used during the delay separating stimuli, in order to determine the contents of spatial working memory in this task. A two-task situation was created. On the primary task, two dot arrays were serially presented within a grid, leaving one space empty, which subjects identified. On the secondary task, instead of the second array, a discrimination probe was presented. Integration accuracy increased through delays of 1,500 msec, revealing an estimate of the time required to form an optimal memory trace for integration. Once the memory trace was formed (but not before), response time to the probe was faster if it was presented in a location previously occupied by a dot from Array 1. This indicates that during the delay separating the arrays, the subjects assigned spatial attention to the locations occupied by the first array and actively maintained the leading array in working memory. Implications for theories of visual processing and memory are discussed.

Attention↗

PubMed2003

Simultaneous spatial updating in nested environments.

When one moves, the spatial relationship between oneself and the entire world changes. Spatial updating refers to the cognitive process that computes these relationships as one moves. In two experiments, we tested whether spatial updating occurs automatically for multiple environments simultaneously. Participants turned relative to either a room or the surrounding campus buildings and then pointed to targets in both the environment in which they turned (updated environment) and the other environment (nonupdated environment). The participants automatically updated the room targets when they moved relative to the campus, but they did not update the campus targets when they moved relative to the room. Thus, automatic spatial updating depends on the nature of the environment. Implications for theories of spatial learning and the structure of human spatial representations are discussed.

Attention↗

PubMed2002

Switching between environmental representations in memory.

In everyday life we accomplish tasks that require the storage and access of mental representations of different environments that we are not currently perceiving. Past research has suggested that environments are encoded by a series of independent representations that are organized in memory. Three experiments tested this idea further by asking whether multiple representations of environments can be accessed simultaneously. Using a cued task-set switching paradigm, subjects judged spatial relationships between target locations in two familiar environments. Response times were longer when successive trials probed different environments, an effect not due to switching between semantic categories or semantic priming, suggesting that representations of environments are accessed sequentially. Implications for various hypotheses concerning the properties of environmental representations are discussed.

Adult↗

PubMed2002

Temporal integration between visual images and visual percepts.

Using a temporal integration task, subjects in 5 experiments were expected to combine information from temporally separated visual presentations. Evidence from these experiments indicated that perceptual information can be integrated with previously generated and currently maintained visual images to form a representation that contains information from each source. Properties and limitations of this integration process were also explored, including the time required to generated the image, the speed at which percepts were integrated with images, and the capacity of the representation. Implications for theories of visual processing and memory are discussed.

Analysis of Variance↗

PubMed2002

Walking, looking to the side, and taking curved paths.

In two experiments, viewers judged heading from displays simulating locomotion through tree-filled environments, with gaze off to the side. They marked their heading with a mouse-controlled probe at three different depths. When simulated eye or head rotation generally exceeded 0.5 deg/sec, there was reliable curvature in perceived paths toward the fixated object. This curvature, however, was slight even with rotation rates as great as 2.6 deg/sec. Best-fit paths to circular arcs had radii of 1.8 km or greater. In a third experiment, pedestrians walked with matched gaze to the side. Measured curvature in the direction of gaze corresponded to a circular radius of about 1.3 km. Thus, at minimum, vision scientists need not worry about perceived path curvature in this situation; real path curvatures are about the same. However, at present, we can make no claim that the same mechanisms necessarily govern the two results.

Adult↗

PubMed2002

Object recognition is mediated by extraretinal information.

Many previous studies of object recognition have found view-dependent recognition performance when view changes are produced by rotating objects relative to a stationary viewing position. However, the assumption that an object rotation is equivalent to an observer viewpoint change ignores the potential contribution of extraretinal information that accompanies observer movement. In four experiments, we investigated the role of extraretinal information on real-world object recognition. As in previous studies focusing on the recognition of spatial layouts across view changes, observers performed better in an old/new object recognition task when view changes were caused by viewer movement than when they were caused by object rotation. This difference between viewpoint and orientation changes was due not to the visual background, but to the extraretinal information available during real observer movements. Models of object recognition need to consider other information available to an observer in addition to the retinal projection in order to fully understand object recognition in the real world.

Attention↗