Academic journal article Human Factors

Artificial Looming Yields Improved Performance over Lateral Motion: Implications for Stereoscopic Display Techniques

Academic journal article Human Factors

Artificial Looming Yields Improved Performance over Lateral Motion: Implications for Stereoscopic Display Techniques

Article excerpt

INTRODUCTION

In the natural world, it is important for organisms to respond effectively to looming objects because failure to do so could result in the organism's demise. Once an organism is aware of an approaching object, it can take evasive action to safeguard against a harmful collision. Ecologically, one would expect looming objects to be perceptually salient, and this is found to be the case in the laboratory, where distinct neural motion detection systems serving this purpose have been discovered (Barlow, Blakemore, & Pettigrew, 1967; Regan & Beverley, 1973a, 1973c).

The presentation of looming stimuli might be expected to assist human performance in tasks requiring an operator's attention to be drawn to a particular display item. Although various methods of attentional cuing can be used (e.g., suddenly presenting a display item; see Yantis, 1996), artificially looming stimuli have the special characteristic of not interfering with displayed information. Hence use of looming as an attentional cue can be accomplished in conjunction with other attentional cuing manipulations. It has already been demonstrated that the addition of binocular disparity information to other cuing methods can assist human performance in a number of tasks (Nakayama & Silverman, 1984; Sollenberger & Milgram, 1993).

Several visual cues indicate that an item is quickly approaching the perceiver. The increasing size of the object, changes in the grain of textures on the object's surface, altered gradients of illumination on the object, and changes in accommodation and occlusion are all dynamic indicators of motion toward the perceiver. These cues are also monocular depth cues in that they provide three-dimensional information that can be perceived when viewing with a single eye. Binocular depth cues, however, require the integration of information from both eyes and include convergence and binocular disparity.

The current paper deals with only the last of these cues for depth: binocular disparity. Because peoples' eyes are separated (by about 6 cm on average), each eye receives a different view of the world. Binocular, or retinal, disparity refers to the geometrical difference that results in the left and right retinal images because of the eyes' physical separation.

When each eye is presented with a slightly different view of the world, most people are able to fuse the views into a single stereoscopic image that appears to extend in depth (Julesz, 1971). This demonstrates that disparity information alone is sufficient to convey the perception of depth, a finding that is corroborated by the discovery of separate neural systems devoted to the processing of binocular disparity information (Barlow et al., 1967; Regan, Beverley, & Cynader, 1979).

Changes in retinal disparity alone are capable of providing sufficient information to produce the perception of looming in human observers (Regan & Spekreijse, 1970). That is, by simply changing the retinal disparity of the images of an object being delivered to the left and right eyes, without supplying any of the other generally correlated indicators of a change in depth (e.g., perspective and changes in surface image information), the perception of looming is reported by the observer. This effect will be referred to as artificial looming in the current paper, to reflect the fact that stimuli of this sort do not occur in the natural world.

Artificial looming is unlike natural looming in at least two ways. First, with artificial looming stimuli, the size of the image on the retina does not increase, as is always the case with natural stimuli. Second, the change in disparity for artificial looming stimuli may be abrupt as opposed to gradually increasing, as is necessarily the case for real objects that move through space over time.

Advances in computer display technology are allowing for the relatively inexpensive addition of binocular disparity information to everyday applications. …

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