Human four-dimensional spatial intuition in virtual reality.

It is a long-lasting question whether human beings, who evolved in a physical world of three dimensions, are capable of overcoming this fundamental limitation to develop an intuitive understanding of four-dimensional space. Techniques of analogy and graphical illustration have been developed with some subjective reports of success. However, there has been no objective evaluation of such achievements. Here, we show evidence that people with basic geometric knowledge can learn to make spatial judgments on the length of, and angle between, line segments embedded in four-dimensional space viewed in virtual reality with minimal exposure to the task and no feedback to their responses. Their judgments incorporated information from both the three-dimensional (3-D) projection and the fourth dimension, and the underlying representations were not algebraic in nature but based on visual imagery, although primitive and short lived. These results suggest that human spatial representations are not completely constrained by our evolution and development in a 3-D world. Illustration of the stimuli and experimental procedure (as video clips) and the instruction to participants (as a PDF file) may be downloaded from http://pbr.psychonomic-journals.org/content/supplemental.

Temporal tuning and attentional gating: two distinct attentional mechanisms on the perception of rapid serial visual events.

We examined the relationship between two different attention limitations on the perception of rapid events: the attentional awakening (AA, an inability to successfully process a target when it appears early on in a rapid stream of events) and the attentional blink (AB, an inability to successfully process a second target when it appears shortly after a first target [T1]). In four experiments, we failed to find a relationship between the magnitudes of these phenomena. Furthermore, we found two manipulations that selectively modulated the magnitude of each effect without altering the magnitude of the second effect: Expected range of possible rapid serial visual presentation lengths modulated the AA (but not the AB), suggesting that the AA reflects an attentional setup cost for perceiving a protracted series of rapid events, whereas the number of possible T1 positions in the stream modulated the magnitude of the AB (but not the magnitude of the AA). Our results suggest that, despite the surface similarities between the two phenomena, different mechanisms are responsible for these two attentional limitations: Whereas the AA reflects a starting cost associated with the time required to temporally tune attention to the stimulus stream, the AB reflects a blocking of undesired stimuli, aimed at protecting consolidation of T1 processing.

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.

Fruitful visual search: inhibition of return in a virtual foraging task.

Inhibition of return (IOR) has long been viewed as a foraging facilitator in visual search. We investigated the contribution of IOR in a task that approximates natural foraging more closely than typical visual search tasks. Participants in a fully immersive virtual reality environment manually searched an array of leaves for a hidden piece of fruit, using a wand to select and examine each leaf location. Search was slower than in typical IOR paradigms, taking seconds instead of a few hundred milliseconds. Participants also made a speeded response when they detected a flashing leaf that either was or was not in a previously searched location. Responses were slower when the flashing leaf was in a previously searched location than when it was in an unvisited location. These results generalize IOR to an approximation of a naturalistic visual search setting and support the hypothesis that IOR can facilitate foraging. The experiment also constitutes the first use of a fully immersive virtual reality display in the study of IOR.

The role of highlighting in visual search through maps.

Two experiments were conducted in which participants performed a vehicle dispatching task. The intensity of one information source (vehicles in Experiment 1, destinations in Experiment 2) was varied to examine the effects of salience and discrimination on both searching for and processing the information in a cluttered display. Response times were recorded for questions either requiring focused attention on or divided attention between the different information domains in the map. The results of the present experiments indicate that it is possible to declutter a display without erasing any information. By 'lowlighting' one information domain and keeping the other domain at a fairly high intensity level, dividing attention between the information sources is optimal, as is focusing attention on either of the information domains exclusively. These results are discussed in conjunction with a computational model of confusion and salience which serves to predict search and integration performance in a cluttered display with separate domains of information displayed at different intensities.