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Previous research suggests that peripheral target detection is modulated by viewing distance and distance simulated by pictorial cues and optic flow. In the latter case, it is unclear what cues contribute to the effect of distance. The current study evaluated the effect of distance on peripheral detection in a virtual three-dimensional environment. Experiments 1-3 used a continuous, dynamic central task that simulated observers traveling either actively or passively through a virtual environment following a car. Peripheral targets were flashed on checkerboard-covered walls to the left and right of the path of motion, at a near and a far distance from the observer. The retinal characteristics of the targets were identical across distances. Experiment 1 found more accurate and faster detection for near targets compared to far targets, especially for larger eccentricities. Experiment 2 equated the predictability of target onset across distances and found the near advantage for larger eccentricities in accuracy but a much smaller effect in reaction time (RT). Experiment 3 removed the checkerboard background implemented in Experiments 1 and 2, and Experiment 4 manipulated several static, monocular cues. Experiments 3 and 4 found that the variation in the density of the checkerboard backgrounds could explain the main effect of distance on accuracy but could not completely account for the interaction between target distance and eccentricity. These results suggest that attention is modulated by target distance, but the effect is small. Finally, there were consistent divided attention costs in the central car-following task but not the peripheral detection task.

Background/Study Context: Reduced processing speed pervades a great many aspects of human aging and cognition. However, little is known about one aspect of cognitive aging in which speed is of the essence, namely, the speed with which older adults can deploy attention in response to a cue., Methods: The authors compared rapid temporal modulation of cued visual attention in younger (M age  = 22.3 years) and older (M age  = 68.9 years) adults. On each trial of a short-term memory task, a cue identified which of two briefly presented stimuli was task relevant and which one should be ignored. After a short delay, subjects demonstrated recall by reproducing from memory the task-relevant stimulus. This produced estimates of (i) accuracy with which the task-relevant stimulus was recalled, (ii) the influence of stimuli encountered on previous trials (a prototype effect), and (iii) the influence of the trial's task-irrelevant stimulus., Results: For both groups, errors in recall were considerably smaller when selective attention was cued before rather than after presentation of the stimuli. Both groups showed serial position effects to the same degree, and both seemed equally adept at exploiting the stimuli encountered on previous trials as a means of supplementing recall accuracy on the current trial., Conclusion: Younger and older subjects may not differ reliably in capacity for cue-directed temporal modulation of selective attention, or in ability to draw on previously seen stimuli as memory support.

Many sensory and cognitive changes accompany normal ageing, including changes to visual attention. Several studies have investigated age-related changes in the control of attention to specific locations (spatial orienting), but it is unknown whether control over the distribution or breadth of attention (spatial focus) also changes with age. In the present study, we employed a dual-stream attentional blink task and assessed changes to the spatial distribution of attention through the joint consequences of temporal lag and spatial separation on second-target accuracy. Experiment 1 compared the rate at which attention narrows in younger (mean age 22.6, SD 4.25) and older (mean age 66.8, SD 4.36) adults. The results showed that whereas young adults can narrow attention to one stream within 133 ms, older adults were unable to do the same within this time period. Experiment 2 showed that older adults can narrow their attention to one stream when given more time (266 ms). Experiment 3 confirmed that age-related changes in retinal illuminance did not account for delayed attentional narrowing in older adults. Considered together, these experiments demonstrate that older adults can narrow their attentional focus, but that they are delayed in initiating this process compared to younger adults. This finding adds to previously reported reductions in attentional dynamics, deficits in inhibitory processes, and reductions in posterior parietal cortex function that accompany normal ageing.

Previous research suggests that visual attention can be allocated to locations in space (space-based attention) and to objects (object-based attention). The cueing effects associated with space-based attention tend to be large and are found consistently across experiments. Object-based attention effects, however, are small and found less consistently across experiments. In three experiments we address the possibility that variability in object-based attention effects across studies reflects low incidence of such effects at the level of individual subjects. Experiment 1 measured space-based and object-based cueing effects for horizontal and vertical rectangles in 60 subjects comparing commonly used target detection and discrimination tasks. In Experiment 2 we ran another 120 subjects in a target discrimination task in which rectangle orientation varied between subjects. Using parametric statistical methods, we found object-based effects only for horizontal rectangles. Bootstrapping methods were used to measure effects in individual subjects. Significant space-based cueing effects were found in nearly all subjects in both experiments, across tasks and rectangle orientations. However, only a small number of subjects exhibited significant object-based cueing effects. Experiment 3 measured only object-based attention effects using another common paradigm and again, using bootstrapping, we found only a small number of subjects that exhibited significant object-based cueing effects. Our results show that object-based effects are more prevalent for horizontal rectangles, which is in accordance with the theory that attention may be allocated more easily along the horizontal meridian. The fact that so few individuals exhibit a significant object-based cueing effect presumably is why previous studies of this effect might have yielded inconsistent results. The results from the current study highlight the importance of considering individual subject data in addition to commonly used statistical methods.

The current study tested the widespread assumption that holistic processing is important for the identification of upright faces. In two experiments, we show that (a) there are large individual differences in the magnitude of the composite face effect and face-identification accuracy and (b) the correlation between the magnitude of the composite face effect and face-identification accuracy is essentially zero. These findings are inconsistent with the claim that holistic processing, as indexed by the composite face effect, significantly influences accuracy in a face-identification task.

People with autism spectrum disorders appear to have some specific advantages in visual processing, including an advantage in visual search tasks. However, executive function theory predicts deficits in tasks that require divided attention, and there is evidence that people with autism have difficulty broadening their attention (Mann & Walker, 2003). We wanted to know how robust the known attentional advantage is. Would people with autism have difficulty dividing attention between central and peripheral tasks, as is required in the Useful Field of View task, or would they show an advantage due to strengths in visual search? Observers identified central letters and localized peripheral targets under both focused- and divided-attention conditions. Participants were 20 adults with high-functioning autism and Asperger's syndrome and 20 adults matched to the experimental group on education, age, and IQ. Contrary to some predictions, individuals with autism tended to show relatively smaller divided-attention costs than did matched adults. These results stand in stark contrast to the predictions of some prevalent theories of visual and cognitive processing in autism.

Using a linear cue combination framework, we develop a measure of selective attention that describes the relative weight that an observer assigns to attended and unattended parts of a stimulus when making perceptual judgments. We call this measure attentional weight. We present two methods for measuring attentional weight by calculating the trial-by-trial correlation between the strength of attended and unattended parts of a stimulus and the observer's responses. We illustrate these methods in three experiments that investigate whether observers can direct selective attention according to contrast polarity when judging global direction of motion or global orientation. We find that when observers try to judge the global direction or orientation of the parts of a stimulus with a given contrast polarity (white or black), their responses are nevertheless strongly influenced by parts of the stimulus that have the opposite contrast polarity. Our measure of selective attention indicates that the influence of the opposite-polarity distractors on observers' responses is typically 65% as strong as the influence of the targets in the motion task, and typically 25% as strong as the targets in the orientation task, demonstrating that observers have only a limited ability to direct attention according to contrast polarity. We discuss some of the advantages of using a linear cue combination framework to study selective attention.

There is considerable evidence indicating that cuing a specific portion of an object results in the entire object's being attended to. In the present study, we examined whether previous experience with an object could halt perceptual (i.e., amodal) completion. In Experiment 1, two parallel rectangles were initially displayed, and then the middle portions of these objects were occluded. Attentional cuing effects were found for both discrete portions of the completed rectangles. In the final two experiments, four discrete objects were initially displayed, followed by the same occluder as that used in the first experiment. The appearance of the occluder (500 msec before the cue in Experiment 2,100 msec before the cue in Experiment 3) allowed the four discrete objects to be completed into two rectangles. Attentional cuing effects were found for the completed rectangles in both experiments, indicating that previous experience was not sufficient to halt the amodal completion of objects.

Object perception remains constant in the face of much retinal image variability. One way to achieve such constancy is to represent objects with respect to a reference frame, and many theories of object recognition assume that, among other factors, observers use objects' primary axes of elongation to derive reference frames. However, the limited research directly addressing this assumption suggests that the role of axis of elongation may not be as central as previously though (Palmer, 1990; Quinlan & Humphreys, 1993). The present study re-examines elongation's role in determining reference frames, adapting Palmer's paradigm to determine the extent to which surrounds bias the perception of ambiguously oriented objects: equilateral triangles. When surrounds were oriented inconsistently with experimentally constrained correct responses, response times increased with surrounds' elongation. These results hold for both symmetric and asymmetric surrounds, suggesting that elongation alone is sufficient to construct a reference frame for object perception.

Can shape differences drive apparent motion? Results from previous research are equivocal. Much of the confusion may be due to the use of relatively complex stimuli: letters or geometric shapes, comprising many spatial frequencies, phases, orientations, and contrasts. We focus on relatively simple stimuli: Gaussian damped f+nf compound sinewave gratings. We examine whether relative phase differences, which are critical for shape perception, can drive apparent motion. We find that some, but not all, phase differences can drive apparent motion. Specifically, stimuli that are easily discriminable and perceptually dissimilar can affect the solution of the correspondence problem. In this case, observers consistently perceive stimuli in one frame moving to the position of perceptually similar stimuli in the next frame. This general result holds over a wide range of spatial frequencies, orientations, and contrasts. Implications for theories of motion processing are discussed.

The visual information that specifies three-dimensional objects is often incomplete because objects occlude parts of themselves and other objects. Yet people rarely have difficulty perceiving complete, three-dimensional forms. Somehow the visual system seems to 'complete' partially specified objects. The perceptual processes underlying this seemingly effortless and immediate completion are poorly understood. Sekuler and Palmer designed in 1992 the primed-matching paradigm for the objective study of completion effects and their microgenesis. Results from the paradigm suggest that global processes may play a role early in perceptual completion, and that local processes dominate only under limited conditions of figural regularity and orientation. These results are not consistent with purely local or purely global theories of completion. The findings have implications for object perception and representation.

To determine how the visual system represents information about change in target direction, we studied the detection of such change under conditions of varying stimulus certainty. Target direction was either held constant over trials or was allowed to vary randomly. When target direction was constant the observer could be certain about that stimulus characteristic; randomizing the target direction rendered the observer uncertain. We measured response times (RTs) to changes in target direction following initial trajectories of varying time and distance. In different conditions, the observer was uncertain about either the direction of the initial trajectory, or the direction of change or both. With brief initial trajectories in random directions, uncertainty about initial direction elevated RTs by 50 ms or more. When the initial trajectories were at least 500 ms, this directional uncertainty ceased to affect RTs; then, only uncertainty about the direction of change affected RTs. We discuss the implications of these results for (i) schemes by which the visual system might code directional change; (ii) the visual integration time for directional information; and (iii) adaptational processes in motion perception.