Previous research on visually induced self-motion found that stimulation of the central visual field (up to 30 degrees in diameter) results in perceived object motion while self-motion requires peripheral stimulation. In the present study, perceived self-motion was induced with a radially expanding pattern simulating observer motion through a space filled with dots, with visual angles of 7.5 degrees, 10.6 degrees, 15 degrees, and 21.2 degrees. Speed and texture density were also varied. The duration of reported self-motion (a) decreased with increased speed, (b) failed to increase with increased visual angle, and (c) decreased with visual angle at the highest speed level. In a second experiment, subjects rated the perceived depth of the displays. The speed and speed/area interaction effects on judged depth matched those found for induced self-motion. These results suggest an extension of the focal/ambient theory: In addition to a more primitive ambient processing mode that requires peripheral vision, there is a higher level system concerned with ambient processing that functions in the central visual field and uses more complex stimulus information, such as internal depth represented in a radially expanding pattern.

The present study examined age-related differences in multisensory integration and the role of attention in age-related differences in multisensory integration. The sound-induced flash illusion---the misperception of the number of visual flashes due to the simultaneous presentation of a different number of auditory beeps---was used to examine the strength of multisensory integration in older and younger observers. The effects of integration were examined when discriminating 1–3 flashes, 1–3 beeps, or 1–3 flashes presented with 1–3 beeps. Stimulus conditions were blocked according to these conditions, with baseline (unisensory) performance assessed during the multisensory block. Older participants demonstrated greater multisensory integration--a greater influence of the beeps when judging the number of visual flashes--than younger observers. In a second experiment, the role of attention was assessed using a go/no-go paradigm. The results of Experiment 2 replicated those of Experiment 1. In addition, the strength of the illusion was modulated by the sensory domain of the go/no-go task, though this did not differ by age group. In the visual go/no-go task we found a decrease in the illusion, while in the auditory go/no-go task we found an increase in the illusion. These results demonstrate that older individuals exhibit increased multisensory integration compared to younger individuals. Attention was also found to modulate the strength of the sound-induced flash illusion. However, the results also suggest that attention was not likely to be a factor in the age-related differences in multisensory integration.

The present experiment examined the shape of the attentional gradient in three-dimensional space. Subjects performed a response-compatibility task in which they were instructed to respond to a centrally located target and ignore flanking distractors. The irrelevant distractors were presented at combinations of seven different depths, three different horizontal separations, and three different vertical separations relative to the target. Depth was varied in a stereoscopic display viewed through polarized glasses. Overall, the size of the response-compatibility effect decreased with increased separation in all three dimensions. Interestingly, the response-compatibility effect was larger for horizontal separations than for vertical separations and was larger for crossed disparities than for uncrossed disparities. The results suggest an elliptical focus of attention, with steeper gradients in the vertical dimensions than in the horizontal dimensions. In addition, the results suggest, along the vertical dimension, a steeper gradient for objects located beyond the focus of attention relative to that for objects located between the observer and the focus of attention.Over the past two decades, there has been considerable interest in the dynamics of visual attention. An important focus of this body of research has been the relation between the size of the attentional focus and processing efficiency. For example, models based on a spotlight analogy have argued that stimuli that fall within the beam of the spotlight receive full processing, whereas stimuli that are located outside of the boundaries of the spotlight are ignored (Broadbent,

Forty observers participated in a study examining the effect of age on the detection of motion in central and peripheral vision. Detection of lamellar (Experiment 1) and radial flow (Experiment 2) was measured for 20 younger observers and 20 older observers (10 men and 10 women in each group). Motion thresholds were measured for angles of 0 degree, 10 degrees, 20 degrees, and 40 degrees off fovea. The results indicated significant differences between older and younger adults for both motion types. The effect of age was mediated by the gender of the observer as well as the retinal eccentricity of the display. Older women showed higher thresholds for lamellar flow at fovea, consistent with previous findings. The findings suggest that age-related changes in visual information processing are affected by changes in the temporal characteristics of the motion processing system. A model is proposed in which 2 different streams of processing are used for the recovery and use of motion information.

The size offocused attention was assessed within a three-dimensional display. Subjects viewed random-dot stereogram displays in which they responded differentially to vertical and horizontal bars. Adjacent noise elements either were identical to the response target or specified the opposite response. The position of the noise elements was varied in depth according to binocular disparity. Interference by incompatible noise elements decreased with depth separation between the noise elements and response target. In addition, interference was greater for noise elements that were more distant from the observer than from the response target than it was for noise elements that were closer to the observer than to the response target. The implications of these results for a viewer-centered representation of focused attention in depth are discussed. 112An important property of visual processing is the ability to allocate processing resources or attend to locations in the visual field that might contain important information. Considerable research has been conducted to determine the spatial limits of visual attention when subjects are required to attend to information at a specified position in the visual field. B. A. Eriksen and C. W. Eriksen (1974) presented subjects with five simultaneous items in visual displays. The subjects were required to respond to the middle item of each display and to ignore the adjacent noise elements that were present. The response specified by the adjacent set of elements was either compatible or incompatible with the response to the central target. By varying the spatial separation of the noise elements relative to the central target, the size of focused attention could be measured. If the noise elements fell within the focus of attention, reaction time (RT) would be greater when they were incompatible with the response to the central target than when they were compatible.Using this paradigm, B. A. Eriksen and C. W. Eriksen (1974) found that the interfering effects of the incompatible noise elements decreased with greater spatial separations between the target and noise elements up to 1 0•

In the present study an alternative analysis to tau was considered that was based on perceived speed and size and that assumed constant deceleration for the detection of collision events. Observers were presented with displays simulating a 3-D environment with obstacles in the path of observer motion. During the trial, observer motion decelerated at a constant rate and was followed by a blackout prior to the end of the display. Observers had to detect which trials resulted in a collision. The results indicate that collision detection varied as a function of the size of the obstacles, observer speed, and edge rate--findings not predicted by an analysis of tau. The results suggest that observers use an analysis based on speed and size information. A model that assumes constant deceleration is proposed for braking control.

Age-related declines in vision can have a major impact on the health and well-being of an older population. A review of research on aging and vision indicate that these declines occur at multiple levels of the visual system including optics, sensory processing, and perceptual processing, and are not likely to due to a systemic change in brain function (e.g., generalized slowing; common cause hypothesis) as a result of normal aging. In addition, declines in sensory and perceptual processing are not due to low-level explanations such as the amount of light that reaches the retina. Declines in visual performance are due to a variety of distinct factors that include spatial integration and difficulty in processing visual information in the presence of noise. Neurophysiological studies suggest that processing declines may be due in part to changes in cortical inhibition mediated by changes in the level of neurotransmitters associated with inhibition. Despite the widespread declines in function with normal aging recent research suggests that perceptual learning can be used to dramatically improve visual function for older individuals. This research suggests a high degree of plasticity of the visual system among older populations and suggests that perceptual learning is an important tool for the recovery of age-related declines in vision.

The relative effectiveness of the ground surface and other environmental surfaces (the ceiling and sidewalls) in determining perceived layout was investigated in five experiments and a real-world demonstration. In the first three experiments, two vertical or horizontal posts were positioned between two surfaces (ground and ceiling in all three experiments, left wall and right wall in Experiment1), and optical contact was manipulated so that the two surfaces provided contradictory information about the relative distances of the posts. Observers judged which of the two posts appeared to be closer. In Experiment 4, to control the height on the posts at which the distance judgments were made, a blue dot was attached to both vertical posts at varying heights and observers judged which dot appeared closer. In Experiment 5, the posts were replaced by two gray ellipses to eliminate the effects of the regular shape and texture. Our findings were that (1) among all four surfaces tested, observers showed a preference to respond according to the optical contact information provided by the ground surface-a ground dominance effect, (2) this effect did not depend on the height of the posts in the image, (3) as the scene was tilted away from a ground/ceiling orientation, the ground dominance effect decreased, and (4) this effect was not due to the location of the judgment.