Relative Disparity Research Articles

A new binocular cue for absolute distance: Disparity relative to the most distant structure

When an object is presented binocularly at various distances in complete darkness the range of distances is usually underestimated. We found that adding a second object can reduce the extent to which the range of distances is underestimated. However this only happens if the second object is further than the one of which the distance is to be judged. We propose that the relative disparity between the two objects limits the possible distances of the nearer object because the lines connecting the further object to each of the two eyes must converge in the distance.

Disparity in smoking prevalence by education: can we reduce it?

Can an intervention program that is highly effective in reducing the prevalence of an unhealthy behavior in the general population also reduce the disparity among its subgroups? That depends on what measure of disparity is used. Using simple algebraic models, this study demonstrates that disparity measured in terms of relative difference between two groups tends to increase when the prevalence of the behavior is in decline. The study then shows an empirical example, by analyzing the effects of the California tobacco control program on smoking prevalence of two education groups, the lowest (less than 12 years) and the highest (16 years or more). It examines the data from four California Tobacco Surveys covering the years 1996, 1999, 2002, and 2005. The effects of three components of the tobacco control program known to be effective in decreasing prevalence (media, worksite policy, and price) on the two education groups are assessed. The smoking prevalence for the two groups is obtained from these four surveys and a regression line is computed for each education group from 1996 to 2005. Results show that the California program is effective with both low education and high education groups and that the rate of decline in smoking prevalence from 1996 to 2005 is no smaller for the low education group than for the high education group. The paper then discusses that an analysis of disparity based on relative difference, however, could result in misleading recommendations that an intervention like the California tobacco program needs to change from its current whole-population approach to one that focuses on targeting subgroups because it has not reduced disparity. It proposes that research should focus more on increasing the rate of change among less advantage groups and less on the relative disparity compared to some other group.

Is socioeconomic disparity in disability improving among Korean elders?

The purpose of this study was to evaluate whether the socioeconomic disparity in disability status in Korea improved during the decade between 1994 and 2004. Information was obtained from the National Survey of Elders' Life and Welfare Desires in 1994, 1998, and 2004. Age-adjusted disability rates by educational level and income were calculated separately for women and men. Prevalence ratios for disability by education and income were estimated using log-binomial regression. The relative index of inequality (RII) was calculated controlling for age. We also assessed trends in the disability rate as well as the RII p-trend by year. We found that disability rates declined during the decade from 1994 to 2004 among Koreans aged 65 years old or older. Older persons with less education and income exhibited greater decline in their disability than did those with higher socioeconomic status. Although the absolute disparity in disability decreased during the studied decade, the relative disparity for any disability remained stable in terms of both education and income. Despite rapid decreases in socioeconomic inequality among older adults with severe disabilities, older adults with lower socioeconomic status have remained more vulnerable to milder forms of disability during recent years.

Contextual effects on perceived three-dimensional shape

Binocular disparity is a powerful cue for the perception of depth. The accuracy with which observers can judge depth from disparity can, however, be very poor. This has been attributed to difficulties associated with the scaling of disparity to take account of distance ( Johnston, 1991). We test potential strategies that could be used to improve this scaling. Using the depth-to-width ratio task introduced by Bradshaw, Parton, and Eagle (1998), observers adjusted a depth interval to match the vertical distance between two points. The first experiment examined the effect of placing additional visual stimuli between the observer and the target. Despite the potential of these stimuli to provide reliable distance information, the accuracy of depth settings did not change. The second experiment demonstrated that the degree of binocular correlation present in natural images provides useful distance information, and investigated whether this is used by observers in scaling disparity. To do this, we measured whether varying the magnitude of relative disparity presented in the surround of the target affected depth settings. No such effect was observed. We conclude that the effect of information presented in the surrounding context on settings of depth is limited to those situations in which it provides direct information about the distance to the target.

Temporal Trends in Geographic Disparities in Small-Area Breast Cancer Incidence and Mortality, 1988 to 2005

A goal of Healthy People 2010 was to reduce health disparities. We determined the extent of reductions in geographic disparities in five breast cancer screening indicators. We examined the extent of reductions in geographic disparities in five breast cancer screening indicators using data about women ages 40 years and older from 200 counties in the 1988 to 2005 Surveillance, Epidemiology, and End Results Program database. County-level trends in five breast cancer indicators (in situ, stage I, lymph node-positive, locally advanced, and mortality) were summarized using the estimated annual percentage change. Observed county rates were smoothed using hierarchical Bayesian spatiotemporal methods to calculate measures of absolute and relative geographic disparity and their changes over time. For in situ breast cancer, absolute disparity increased 93.7% during 1988 to 2005. Relative disparity declined 61.5% during the entire study period. Absolute and relative disparity for stage I breast cancer declined 18.5% and 41.4%, respectively. Absolute disparity for lymph node-positive breast cancer declined 37.9% during the study period, whereas relative disparity declined 17.6%. Absolute disparity for locally advanced breast cancer declined 66.5%, whereas relative disparity declined 17.8% during the study period. Absolute disparity in breast cancer mortality declined 60.5%, whereas relative disparity declined 19.8%. Absolute and relative geographic disparities narrowed over time for all breast cancer indicators except for in situ breast cancer. Progress has been made toward reducing geographic disparities in breast cancer outcomes, particularly in advanced-stage breast cancer incidence and mortality rates, although disparities remain.

Contributions of vergence, looming, and relative disparity to the perception of motion in depth

Contributions of vergence, looming, and relative disparity to the perception of motion in depth

Aftereffect of motion-in-depth based on binocular cues: No effect of relative disparity between adaptation and test surfaces

Aftereffect of motion-in-depth based on binocular cues: No effect of relative disparity between adaptation and test surfaces

Perceived stereo depth depends on relative disparity of similarly oriented components in test and reference stimuli

Perceived stereo depth depends on relative disparity of similarly oriented components in test and reference stimuli

The effect of absolute and relative disparity noise on stereoacuity

The effect of absolute and relative disparity noise on stereoacuity

Relative binocular disparity: relative to what?

Relative binocular disparity: relative to what?

Evidence for combination of two methods for measuring relative disparity

Evidence for combination of two methods for measuring relative disparity

MT neurons do not signal relative disparity

Psychophysical studies have shown that relative disparity, the difference of two absolute disparities, is important in perceptual judgements such as stereoacuity. A recent study showed that a small but significant population of V2 neurons signals relative disparity, whereas V1 neurons do not (Thomas et al. 1999, SFN Abstr.). A logical hypothesis is that higher visual areas may contain more neurons signaling relative disparity. In this study, we tested whether MT neurons signal relative disparity between their classical receptive field (CRF) and surrounding regions. We recorded 40 neurons from 3 awake fixating rhesus monkeys. A bi-partite (center/surround) random-dot stereogram was presented, with the center patch covering the neurons' CRF. Dots in both the center and surround patches moved at the neuron's preferred velocity, and both the center and surround disparities varied from trial to trial. Disparity tuning of responses to the center patch was obtained for each of 3–5 surround disparities, and each tuning curve was fit with a gabor function. If neurons signal relative disparity, the tuning curves should shift by an amount equal to the surround disparity. For each possible pair of surround disparities, we calculated the shift in the peak or trough of the tuning curves relative to the difference in surround disparity (shift ratio). A shift ratio of 1 indicates that the shift was equal to the difference in surround disparity, consistent with relative disparity encoding. A shift ratio of 0 indicates that there was no shift with surround disparity, consistent with absolute disparity encoding. Although the median shift ratio of 0.041 was significantly different from 0 (sign-test, p=0.0005, n=209 shifts), the distribution was tightly clustered around 0, and only 1% (2/209) of shift ratios were larger than 0.5. The results suggest that MT neurons do not signal relative disparity in a center-surround configuration, but rather signal the absolute disparity in their CRF.

Contrast interactions imply a second-order basis for relative disparity discrimination

Contrast interactions imply a second-order basis for relative disparity discrimination

Educational Disparities in Mortality Among Adults With Diabetes in the U.S.

OBJECTIVETo measure relative and absolute educational disparities in mortality among U.S. adults with diabetes and to compare their magnitude with disparities observed within the nondiabetic population.RESEARCH DESIGN AND METHODSA total of 85,867 individuals (5,007 with diabetes), aged 35–84 years, who participated in the National Health Interview Survey from 1986 to 1996 were followed for mortality through 31 December 2002. Relative and absolute educational disparities in all-cause, cardiovascular disease (CVD), and non-CVD mortality were measured.RESULTSIn relative terms, the risk of all-cause mortality was 28% higher in diabetic adults with the lowest versus the highest position on the educational scale (relative index of inequality 1.28 [95% CI 1.08–1.53]). This inverse relationship reflected marked disparities in CVD mortality and was found in all age, sex, and race/ethnicity groups except Hispanics. Although substantial, this relative educational gradient in mortality among adults with diabetes was smaller than in the nondiabetic population. In absolute terms, diabetic adults with the lowest position on the educational scale suffered 503 excess deaths per 10,000 person-years of follow-up compared with those with the highest position. These absolute disparities were stronger than in the nondiabetic population. The results were even more striking for CVD mortality.CONCLUSIONSThe risk of mortality differs substantially according to educational level among individuals with diabetes in the U.S. Although relative educational disparities in mortality are weaker in adults with versus without diabetes, their absolute impact is greater and translates into a major mortality burden.

Temporal trends in area socioeconomic disparities in breast-cancer incidence and mortality, 1988–2005

Since an overarching goal of Healthy People 2010 was to eliminate health disparities, we determined temporal trends in socioeconomic disparities in five breast-cancer indicators (in situ, stage I, lymph-node positive, and locally advanced breast-cancer incidence, and breast-cancer mortality) by county socioeconomic deprivation using 1988-2005 population-based breast-cancer data. Using 1988-2005 data from women aged 40 and older from 200 counties in the Surveillance, Epidemiology, and End Results program, we examined trends in temporal disparities in the five breast-cancer indicators across quartiles of county socioeconomic deprivation. County-level trends were summarized using the estimated annual percentage change. Observed county rates were smoothed using Bayesian hierarchical spatiotemporal methods to calculate measures of absolute and relative disparity (using absolute and relative concentration indices) and their changes over time. Large increases in in situ breast cancer rates since 1988 were observed for each of the deprivation quartiles. Absolute and relative disparity both increased over time, suggesting increasing disparities across levels of county deprivation. Absolute and relative concentration indices were near zero for the other four breast-cancer indicators, suggesting no disparities among the four quartiles of county deprivation during 1988-2005. Efforts to target counties aimed at increasing breast-cancer screening based on their level of deprivation will not likely be beneficial.

Pinna Cues Determine Orienting Response Modes to Synchronous Sounds in Elevation

To program a goal-directed orienting response toward a sound source embedded in an acoustic scene, the audiomotor system should detect and select the target against a background. Here, we focus on whether the system can segregate synchronous sounds in the midsagittal plane (elevation), a task requiring the auditory system to dissociate the pinna-induced spectral localization cues. Human listeners made rapid head-orienting responses toward either a single sound source (broadband buzzer or Gaussian noise) or toward two simultaneously presented sounds (buzzer and noise) at a wide variety of locations in the midsagittal plane. In the latter case, listeners had to orient to the buzzer (target) and ignore the noise (nontarget). In the single-sound condition, localization was accurate. However, in the double-sound condition, response endpoints depended on relative sound level and spatial disparity. The loudest sound dominated the responses, regardless of whether it was the target or the nontarget. When the sounds had about equal intensities and their spatial disparity was sufficiently small, endpoint distributions were well described by weighted averaging. However, when spatial disparities exceeded approximately 45 degrees, response endpoint distributions became bimodal. Similar response behavior has been reported for visuomotor experiments, for which averaging and bimodal endpoint distributions are thought to arise from neural interactions within retinotopically organized visuomotor maps. We show, however, that the auditory-evoked responses can be well explained by the idiosyncratic acoustics of the pinnae. Hence basic principles of target representation and selection for audition and vision appear to differ profoundly.

The horizontal disparity direction vs. the stimulus disparity direction in the perception of the depth of two-dimensional patterns

Horizontal binocular disparity has long been the conventional predictor of stereo depth. Surprisingly, an alternative predictor fairs just as well. This alternative predicts the relative depth of two stimuli from the relation between their disparity vectors, without regard to horizontal disparities. These predictions can differ; horizontal disparities accurately predict the perceived depth of a grating and a plaid only when the grating is vertical, while the vector calculation accurately predicts it at all except near-horizontal grating orientations. For spatially two-dimensional stimulus pairs, such as plaids, dots, and textures, the predictions cannot be distinguished when the stimuli have the same disparity direction or when the disparity direction of one of the stimuli is horizontal or has a magnitude of zero. These are the conditions that have prevailed in earlier studies. We tested whether the perceived depth of two-dimensional stimuli depends on relative horizontal disparity magnitudes or on relative disparity magnitudes along a disparity axis. On both measures tested-depth matches and depth-interval matches-the perceived depth of plaids varied with their horizontal disparities and not with disparity direction differences as observed for grating-plaid pairs. Differences in disparity directions as great as 120 degrees did not affect depth judgments. This result, though opposite the grating-plaid data, is consistent with them and provides a view into the construction of orientation-invariant disparity representations.

Identification of racial disparities in breast cancer mortality: does scale matter?

BackgroundThis paper investigates the impact of geographic scale (census tract, zip code, and county) on the detection of disparities in breast cancer mortality among three ethnic groups in Texas (period 1995-2005). Racial disparities were quantified using both relative (RR) and absolute (RD) statistics that account for the population size and correct for unreliable rates typically observed for minority groups and smaller geographic units. Results were then correlated with socio-economic status measured by the percentage of habitants living below the poverty level.ResultsAfrican-American and Hispanic women generally experience higher mortality than White non-Hispanics, and these differences are especially significant in the southeast metropolitan areas and southwest border of Texas. The proportion and location of significant racial disparities however changed depending on the type of statistic (RR versus RD) and the geographic level. The largest proportion of significant results was observed for the RD statistic and census tract data. Geographic regions with significant racial disparities for African-Americans and Hispanics frequently had a poverty rate above 10.00%.ConclusionsThis study investigates both relative and absolute racial disparities in breast cancer mortality between White non-Hispanic and African-American/Hispanic women at the census tract, zip code and county levels. Analysis at the census tract level generally led to a larger proportion of geographical units experiencing significantly higher mortality rates for minority groups, although results varied depending on the use of the relative versus absolute statistics. Additional research is needed before general conclusions can be formulated regarding the choice of optimal geographic regions for the detection of racial disparities.

1P1-E03 マルチスリット光を用いた小型距離画像センサの開発と障害物検出への応用

Detection of obstacles on a plane is important for a mobile robot that moves in a living space, especially for a humanoid that falls down even with a small obstacle. In this paper, a range image sensor for detecting small obstacles on a plane is constructed using a multi-slit laser projector. The sensor consists of a commercially available laser projector and a CCD camera. It measures a relative disparity map (RDMap) whose measurement errors are not affected by the distance. From the obtained RDMap, a plane is estimated using LMedS and regions out of the plane are detected as obstacles. Experiments show that the constructed sensor can detect small obstacles such as a LAN cable with the proposed methods.

Cue conflict between disparity change and looming in the perception of motion in depth

We hypothesized that it is the conflict between various cues to distance that have produced results purportedly showing that vergence eye movements induced by disparity change are not an effective cue for depth. Single and compound stimuli were used to examine the perceived motion in depth (MID) produced by simulated motion oscillations specified by disparity, relative disparity, and/or looming. Estimations of the extent of MID and binocularly recorded eye movements showed that the vergence induced by disparity change is indeed an effective cue for motion in depth in conditions where looming information does not conflict with it. When looming and disparity are in conflict, looming is the stronger cue.