Investigating spatial vision and dynamic attentional selection using a gaze-contingent multiresolutional display

This study examined spatial vision and attentional selection using a gaze-contingent multiresolutional display, with a dynamic, gaze-centered, high-resolution window and lower resolution periphery. Visual search times and eye movements from 15 participants in a 3 x 3 design (Window Radius x Peripheral Resolution) suggest that contrast sensitivity as a function of retinal eccentricity affects attentional selection and visual processing. Smaller windows led to longer search times and shorter saccades; lower peripheral resolution also shortened saccades (all ps < .05) as a result of avoiding fixating degraded areas. Fixation durations, although longer for smaller windows (p < .05), were unaffected by whether the next saccade went within or outside the window. These results are explained through (a) competition among potential saccade targets where above-threshold filtering reduces an object's relative salience and (b) generally disrupted visual processing.     

Direct measurement of the system latency of gaze-contingent displays

Gaze-contingent displays combine a display device with an eyetracking system to rapidly update an image on the basis of the measured eye position. All such systems have a delay, the system latency, between a change in gaze location and the related change in the display. The system latency is the result of the delays contributed by the eyetracker, the display computer, and the display, and it is affected by the properties of each component, which may include variability. We present a direct, simple, and low-cost method to measure the system latency. The technique uses a device to briefly blind the eyetracker system (e.g., for video-based eyetrackers, a device with infrared light-emitting diodes (LED)), creating an eyetracker event that triggers a change to the display monitor. The time between these two events, as captured by a relatively low-cost consumer camera with high-speed video capability (1,000 Hz), is an accurate measurement of the system latency. With multiple measurements, the distribution of system latencies can be characterized. The same approach can be used to synchronize the eye position time series and a video recording of the visual stimuli that would be displayed in a particular gaze-contingent experiment. We present system latency assessments for several popular types of displays and discuss what values are acceptable for different applications, as well as how system latencies might be improved.     

Implicit processing during change blindness revealed with mouse-contingent and gaze-contingent displays

People often miss salient events that occur right in front of them. This phenomenon, known as change blindness, reveals the limits of visual awareness. Here, we investigate the role of implicit processing in change blindness using an approach that allows partial dissociation of covert and overt attention. Traditional gaze-contingent paradigms adapt the display in real time according to current gaze position. We compare such a paradigm with a newly designed mouse-contingent paradigm where the visual display changes according to the real-time location of a user-controlled mouse cursor, effectively allowing comparison of change detection with mainly overt attention (gaze-contingent display; Experiment 2) and untethered overt and covert attention (mouse-contingent display; Experiment 1). We investigate implicit indices of target detection during change blindness in eye movement and behavioral data, and test whether affective devaluation of unnoticed targets may contribute to change blindness. The results show that unnoticed targets are processed implicitly, but that the processing is shallower than if the target is consciously detected. Additionally, the partial untethering of covert attention with the mouse-contingent display changes the pattern of search and leads to faster detection of the changing target. Finally, although it remains possible that the deployment of covert attention is linked to implicit processing, the results fall short of establishing a direct connection.     

Automatic attraction of attention to former targets in visual displays of letters

Shiffrin and Schneider (1977, Experiment 4d) reported that after consistent training in search for particular alphanumeric characters, presentation of one of these characters (former targets) as a distractor impeded detection of simultaneously presented current targets. Even if presented in an irrelevant display location, the former target appeared to attract attention. Here, we analyze weaknesses in the design of Experiment 4d and report four follow-up experiments ranging from a fairly close replication of the original multiframe experiment to a rather conventional single-frame search study. In each experiment, presentation of former targets consistently impeded detection of simultaneously presented current targets. The results suggest that automatic attention attraction to individual alphanumeric characters develops not only in the special experimental paradigm used by Shiffrin and Schneider, but also in standard visual search tasks. The fact that attention appeared to be attracted by shapes as complex as individual letters supports the assumption that simultaneously presented visual stimuli can be compared in parallel against memory representations of alphanumeric characters.     

Search reaction time for single targets in multiletter stimuli with brief visual displays

The same set of Ss was run In an LT (single late target letter followed an earher multiletter display) and an ET (single early target preceded a later multiletter display) condition. On one-half the trials, the multiletter set included the target. and on the other half, the target was absent. The task of S was to push the “yes” (“no”) button if the target was present (absent), and reaction times were recorded. The most plausible processing model assumed that LT comparisons took place in a verbal-acoustic store and that ET comparisons took place in a visual store. It further assumed that processing within these stores was self-terminating, with rates that differed on “same” and “different” comparisons and which changed as the multiletter set increased. Classes of serial and parallel models that are falsified or supported by the present and similar data are discussed.     

Automated gaze-contingent objects elicit orientation following in 8-month-old infants

The current study tested whether the purely amodal cue of contingency elicits orientation following behavior in 8-month-old infants. We presented 8-month-old infants with automated objects without human features that did or did not react contingently to the infants' fixations recorded by an eye tracker. We found that an object's occasional orientation toward peripheral targets was reciprocated by a congruent visual orientation following response by infants only when it had displayed gaze-contingent interactivity. Our finding demonstrates that infants' gaze-following behavior does not depend on the presence of a human being. The results are consistent with the idea that, in 8-month-old infants, the detection of contingent reactivity, like other communicative signals, can itself elicit the illusion of being addressed.     

The gaze-contingent moving window in reading: Development and review

The development of the gaze-contingent moving window paradigm (McConkie & Rayner, 1975, 1976) is discussed and the results of the earliest research are reviewed. The original work suggested that the region from which readers can obtain useful information during an eye fixation in reading, or the perceptual span, was asymmetric around the fixation point, and extended from 3–4 letter spaces to the left of fixation to about 14–15 letter spaces to the right of fixation. Subsequent research which substantiated these findings is discussed. Then more recent research using the moving window paradigm to investigate the following topics (1) effects of reading speed, (2) effects of reading skill, (3) effects of the writing system, (4) effects due to age, (5) effects related to deafness, and (5) effects related to schizophrenia is discussed. Finally, some extensions of gaze-contingent paradigms to areas other than reading are discussed.     

Status reporting of "eyes on" and peripheral displays during tracking

In response to external requests, pilots often orally report status information read from scattered visual displays while simultaneously controlling an aircraft. For an experimentally controlled "status-reporting" task, we found that the input frequency on a concurrent-tracking task and the task stream-related factors of the rate, uncertainty, and timing of requests showed few significant effects on mean performance times and standard deviations. Tracking performance did vary greatly between the different phases of the "status-reporting" task, the different types of displays and their locations, and the different tracking-input frequencies. An elementary manual control model produced conformal tracking error means and standard deviations when parameters corresponding to behavioral changes were varied. These results indicated that both the performance time statistics of the "status-reporting" task and the influence of concurrent performance on tracking error can be estimated using simple methods.     

A behavioral task for the validation of a gaze-contingent simulated scotoma

Gaze-contingent displays provide a valuable method in visual research for controlling visual input and investigating its visual and cognitive processing. Although the body of research using gaze-contingent retinal stabilization techniques has grown considerably during the last decade, only few studies have been concerned with the reliability of the specific real-time simulations applied. Using a Landolt ring discrimination task, we present a behavioral validation of gaze-contingent central scotoma simulation in healthy observers. Importantly, behavioral testing is necessary to show whether the simulation impairs foveal processing of visual information. This test becomes even more crucial when researchers are faced with null results in a task performed with the scotoma, as compared with a control condition. It must be ruled out that the lack of behavioral effects results from a type II error caused by improper implementation before conclusions about foveal contributions to the given task may be drawn. In our experiment, the scotoma effectively prevented foveal processing of the visual stimuli, leading to significantly reduced response accuracies, as compared with unimpaired vision. Moreover, the final fixation at the time of the participants’ responses was placed close to the target position in the unimpaired condition, whereas the distance to the target was enhanced with the scotoma, indicating that the observers were not able to discriminate visual target stimuli from distractors, due to the scotoma. The present work presents a validated behavioral testing method for the efficiency of gaze-contingent scotoma simulations, including code for implementation. In addition, solutions for common methodological problems are discussed.     

Variation in scatterplot displays

Scatterplots are typically constructed for the purpose of showing the association between two variables. We argue that such scatterplots should not vary in ways that are unrelated to the degree of association. Noting that the publication standards for the preparation of scatterplots are minimal, we review empirical literature that shows that a number of arbitrary features of scatterplots influence the inferences drawn by users. We discuss nine such features. We also review the literature that recommends how scatterplots should be prepared, and we examine 221 scatterplots published in recent journals. There was considerable variation among those published scatterplots. This article concludes with a call for further standardization by way of flexible guidelines.     

Conventional displays: Evidence for socially mediated costs of threat displays in a lizard

Threat displays are used to settle the vast majority of contests between green anoles (Anolis carolinensis). While these displays have been the subject of a number of studies, very little is understood about the information they convey. Theoretical models divide displays into several types of signals, based on the mechanism that stabilizes their use: 1) performance signals, 2) handicapping signals, or 3) conventional displays. The existence of performance displays has excellent empirical support, as do models of their use. Handicapped signalling models, especially those relating to mate‐choice, have been highly influential, though little evidence suggests that threat displays are, in fact, handicapping. Most threat displays appear to be conventional, but little empirical work documents conventional signalling systems. This study investigated the use of headbob, pushup, and lateral compression displays, and concluded that headbob cadence, a discrete signal with three alternative rhythms, is a conventional display indicating impending escalation. Pushups and lateral compression displays appear not to be handicaps, since neither indicates impending escalation, and they do not correlate with fighting ability or condition. Aggr. Behav. 30:326–341, 2004. © 2004 Wiley‐Liss, Inc.     

Gender displays in portrait photographs

Following the research of Goffman (1976) and Henley (1977) on sex differences in nonverbal behavior, 1,296 portrait photographs from high school and university yearbooks and from the media files of a university were analyzed for sex differences. Females smiled with a significantly greater frequency and expansiveness than males and head canted significantly more than males. Results supporting the hypothesis that males would face the camera more directly than females failed to reach the acceptable significance level. The prediction that persons working in opposite-sex roles would deintensify their gender displays failed to gain support.The author expresses appreciation to Bill Drell and Andrea Wilson for their assistance in data collection.     

Attentional capture in driving displays

Drivers face frequent distraction on the roadways, but little is known about situations placing them at risk of misallocating visual attention. To investigate this issue, we asked participants to search for a red target embedded within simulated driving scenes (photographs taken from inside a car) in three experiments. Distraction was induced by presenting, via a GPS unit, red or green distractors positioned in an irrelevant location at which the target never appeared. If the salient distractor captures attention, visual search should be slower on distractor‐present trials than distractor‐absent trials. In Experiment 1, salient distractors yielded no such capture effect. In Experiment 2, we decreased the frequency of the salient distractor from 50% of trials to only 10% or 20% of trials. Capture effects were almost five times larger for the 10% occurrence group than for the 20% occurrence group. In Experiment 3, the amount of available central resources was manipulated by asking participants to either simultaneously monitor or ignore a stream of spoken digits. Capture effects were much larger for the dual‐task group than for the single‐task group. In summary, these findings identify risk factors for attentional capture in real‐world driving scenes: distractor rarity and diversion of attention.     

Saliency metric for subadditive dissimilarity judgments of rectangles

Previous findings that dissimilarity judgments for rectangles are strongly subadditive, that qualitative individual differences are always present, and that four-parameter psychophysical maps can reproduce the average ratings (Sch?nemann & Lazarte, 1987) are replicated. However, the present study in addition suggests that the metric for bounded response transformation, previously used to restore additivity of responses, has a modest effect on the fits of the psychophysical maps. The differential weighing of the coordinates already incorporates segmental subadditivity predictions into the maps. In fact, the psychophysical maps define a subadditive saliency metric that depends on assigning larger weights to larger coordinates. This constraint on the weights of these maps, together with the response times, allows us to identify a strategy shift when subjects respond to two classes of stimulus pairs: For rectangle-rectangle pairs, subjects center on the shape and size of the rectangles; for square-rectangle pairs, the focus is on height and width.     

Movement perception in computer-driven visual displays

Computer-driven visual displays (CDVDs), like television and movies, produce stroboscopic rather than continuous physical movement. The success with which the perception of motion is produced depends or. factors such as the fineness of the raster and the temporal and spatiai reiationships of the stimulus points. For a given velocity, the more points there are on the movement trajectory, and the closer their spacing, the better is the perceived movement. Moderately slow retinal velocities (on the order of .4 to .8 deg/sec) produce the highest quality of perceived movement. One can discriminate among possible subclasses of movement detectors by presenting a complex sequence of intensities at two or more points and varying their cross correlation. Motion between two areas can be perceived even when there is zero correlation between the spatial patterns in each location. Perceived motion can be of rotation, as well as of translation. The two-dimensional shadow of a rotating three-dimensional wire figure is perceived as a rotating, rigid, three-dimensional wire figure (the kinetic depth effect). A three-dimensional “shadow” of a hypothetical four-dimensional wire figure also has been produced; it was not seen as rigid.