Sex and age modulate the visual perception of distance

The visual perception of long outdoor distances

Many previous studies have investigated visual distance perception, especially for small to moderate distances. Few experiments, however, have evaluated the perception of large distances (e.g., 100 m or more). The studies that have been conducted have found conflicting results (diametrically opposite conclusions). In the current experiment, the functions relating actual and perceived distance were obtained for sixteen adult observers using the method of equal appearing intervals. These functions relating perceived and actual distance were obtained for outdoor viewing in a typical University environment-the experiment was conducted along a sidewalk adjacent to a typical street where campus buildings, trees, street signs, etc., were visible. The overall results indicated perceptual compression of distances in depth so that the stimulus distance intervals appeared significantly shorter than the actual (physical) distance intervals. It is important to note, however, that there were sizeable individual differences-the judgments of half of the observers were relatively accurate, whereas the judgments of the remaining half were inaccurate to varying degrees. The results of the experiment demonstrate that there is no single function that describes how human observers visually perceive large distance intervals in outdoor environments.

Monocular information for perceiving large egocentric distance: A comparison between monocularly blind patients and normally sighted observers

The debate surrounding the advantages of binocular versus monocular vision has persisted for decades. This study aimed to investigate whether individuals with monocular vision loss could accurately and precisely perceive large egocentric distances in real-world environments, under natural viewing conditions, comparable to those with normal vision. A total of 49 participants took part in the study, divided into three groups based on their viewing conditions. Two experiments were conducted to assess the accuracy and precision of estimating egocentric distances to visual targets and the coordination of actions during blind walking. In Experiment 1, participants were positioned in both a hallway and a large open field, tasked with judging the midpoint of self-to-target distances spanning from 5 to 30 m. Experiment 2 involved a blind walking task, where participants attempted to walk towards the same targets without visual or environmental feedback at an unusually rapid pace. The findings revealed that perceptual accuracy and precision were primarily influenced by the environmental context, motion condition, and target distance, rather than the visual conditions. Surprisingly, individuals with monocular vision loss demonstrated comparable accuracy and precision in perceiving egocentric distances to that of individuals with normal vision.

How accurate is the visual estimation of bowel length by endoscopic surgeons?

Background

Measurement of small bowel length is an essential step in performing bariatric surgery. Surgeons need to measure bowel length in order to create alimentary and biliopancreatic limbs. Inaccurate bowel measurement may affect the outcome of surgery. However, it is not clear how accurate the measurement of bowel length is by surgeons.

Methods

Two image quizzes marking certain lengths of jejunum were sent to participants. They were asked to estimate the length of marked bowels in maze quizzes. The Error of estimation, prevalence of significant error (error greater than 30 percent of actual length), and the relationship between different participant characteristics was investigated.

Results

A total of 86 participants answered the questionnaire. The mean error of estimation was 4.62 cm (27%). Twenty-eight participants (33%) had significant errors in estimation of bowel length.

Conclusion

While there are surgeons that can estimate bowel length with decent accuracy, significant errors in estimation of bowel length are not uncommon among surgeons. Surgeons should consider adopting techniques for accurate measurement of the small intestine.

Egocentric distance perception in older adults: Results from a functional magnetic resonance imaging and driving simulator study

The ability to appropriately perceive distances in activities of daily living, such as driving, is necessary when performing complex maneuvers. With aging, certain driving behaviors and cognitive functions change; however, it remains unknown if egocentric distance perception (EDP) performance is altered and whether its neural activity also changes as we grow older. To that end, 19 young and 17 older healthy adults drove in a driving simulator and performed an functional magnetic resonance imaging (fMRI) experiment where we presented adults with an EDP task. We discovered that (a) EDP task performance was similar between groups, with higher response times in older adults; (b) older adults showed higher prefrontal and parietal activation; and (c) higher functional connectivity within frontal and parietal-occipital-cerebellar networks; and (d) an association between EDP performance and hard braking behaviors in the driving simulator was found. In conclusion, EDP functioning remains largely intact with aging, possibly due to an extended and effective rearrangement in functional brain resources, and may play a role in braking behaviors while driving.

Visual distance perception indoors, outdoors, and in the dark

The ability to visually perceive distances in depth was evaluated in two experiments. In both experiments, the observers were required to bisect a distance interval oriented in depth (8 m total extent in Experiment 1 and 7 m in Experiment 2). The purpose of Experiment 1 was to examine the effects of environmental context (indoors in the dark, indoors in the light, and outdoors) and monocular versus binocular viewing. The purpose of Experiment 2 was to manipulate linear perspective to determine its importance for perceiving depth interval magnitudes. In the outdoor environment, the observers' bisection judgments indicated perceptual compression of farther distances similar to that obtained in many previous studies. In contrast, the observers' judgments in the indoor lighted environment were consistent with the perceptual expansion of farther distances. There was also a beneficial effect of binocular viewing upon the precision of the observers' repeated judgments, but the size of this effect was large only within the dark environment. Finally, linear perspective was found to significantly modulate the observers' bisection judgments such that they became accurate only when perspective was available.

Pedestrian estimation of their crossing time on multi-lane roads

Estimation of one's own crossing time is an important process in making road-crossing decisions. This study evaluated the pedestrian's (esp. the elderly) ability to estimate crossing time in a field experiment. The estimated crossing time was measured by an interval production method (participants produced an interval to represent their estimated crossing time) and an imagined crossing method. The results showed that while young pedestrians generally had an accurate estimation of their crossing time, old pedestrians consistently underestimated the crossing time in both methods, especially at a wider road. What's worse, even fast walking cannot compensate for the large underestimation. Further analysis showed that although old pedestrians had the declined motor imagery ability and the worse general timing accuracy, none of them can account for the inaccuracy of estimation. These findings suggest that underestimation of crossing time may be one of the important reasons for the acknowledged risky road crossing decision-making in old pedestrians. It also calls for studies on assistive roadway designs and intervention programs targeting old pedestrians.

Haptic Distance Ratio Estimation: The Geometry of Space Within the Hands

In the current study of haptic distance perception, 20 younger (median age: 22 years) and 20 older adults (median age: 72 years) used active touch to estimate distance ratios(one length relative to another). Nine tactile stimuli were created from wooden dowels; each consisted of two perpendicular dowels. The stimulus distance ratios ranged from 1.0 to 5.0. Each participant used both hands (without vision) to actively explore (30 s) a single stimulus object on every trial. The task was to numerically estimate the distance ratio. Overall, the participants’ judgments were precise; the overall magnitude of the Pearson r correlation coefficient was 0.943 and did not differ for younger and older adults. While the participants’ judgments were precise, they were not completely accurate: The average slope (of the relationship between actual and judged distance ratios) for all participants was significantly greater than 1.0 (1.15). Surprisingly, differences in manual dexterity had no apparent effect on distance ratio estimates. Older adults apparently retain an excellent ability to perceive distances using their sense of touch. Our results also demonstrate that the geometry of haptic space (at the scale of the hand) is approximately Euclidean in nature (and certainly not merely topological, projective, or affine).