Frank Schieber

Vision and Aging

Publisher Summary This chapter provides a contemporary overview of one aspect of sensory aging, namely age-related changes in vision and low-level visual information processing. The ability to cope effectively with the environment begins with the capacity to process sensory input. Indeed, the senses have been carefully crafted by the forces of nature to effortlessly extract critical information from the world. Unfortunately, advancing adult aging brings with it systematic reductions in the efficiency of our sensory systems. This lost efficiency of low-level, automatic processing capacity often necessitates effortful, high-level compensatory processes that may tax already limited cognitive resources. Hence, sensory aging is of potentially great interest at all levels of psychological analysis. This focus on vision does not discount the critical role played by the other major sensory systems. Important domains of investigative inquiry are sampled with a focus on basic aspects of vision and aging that have received significant attention in the research literature during the past decade. Several excellent reviews of the sensory aging literature prior to the contemporary period are also presented in the chapter.

Aging and the Senses

Publisher Summary This chapter describes the sensory and perceptual capacities of the aging adult and relates these changes to ones ability to cope with the demands of the environment. As little information is available that specifically links sensory capacity to mental health, the data presented in the chapter focuses on normative aging. The chapter reviews the age-related structural changes in the visual system, the structural changes in the auditory system and the age-related changes in auditory function, the age-related structural changes in the taste system, the age-related changes in the olfactory system, and the age-related changes in the cutaneous sensory structure. A review of the literature on age-related changes in sensory-perceptual processes leads one to formulate recommendations regarding future research initiatives. Among the most critical considerations are a need to (1) account for the increased between-subject variability observed within older groups, (2) isolate peripheral versus central nervous system contributions to age-related sensory deficits, (3) explore more thoroughly the suprathreshold sensory experience among the elderly, (4) explore how cognitive strategies are employed to compensate for reduced sensory abilities, (5) evaluate demonstrated opportunities for preventing age-related loss of sensory function because of environmental insult and disease, and (6) initiate remediation-based research aimed at optimizing the sensory-perceptual environment to the older individual.

Age and Glare Recovery Time for Low-Contrast Stimuli

The purpose of this study was to obtain a rigorous experimental estimate of the time required to recover from the deleterious effects of glare. Low contrast test stimuli were employed to increase the potential sensitivity of the procedure. Multiple age groups were sampled since susceptibility to glare effects is known to increase with advancing years. Glare recovery time assessments were collected from 12 young, 12 middle-aged and 16 older adults. Subjects were presented with 10 sec exposures to an intense glare source under highly controlled experimental conditions. Upon the offset of the glare exposure period, the time required to regain sensitivity for low contrast test stimuli was measured. Relative to their younger counterparts, older subjects required 3-times longer to recover from glare exposure. These findings suggest that the dynamic components of glare effects must be considered when designing environments - especially where older observers are involved.

The Relationship Between Contrast Sensitivity and the Visual Problems of Older Drivers

Numerous age-related changes in the structure and function of the visual system have been noted in the research literature. However, little is known about the extent to which these visual changes contribute to the problems experienced by older persons in the natural environment. In an attempt to estimate the nature and magnitude of the real-world visual problems which accompany normal adult aging, a large number of male and female participants in the Baltimore Longitudinal Study on Aging (N=397) were examined. They ranged from 22 to 92 years of age with oversampling in the 65+ subgroups. Participants completed a survey designed to assess the magnitude of visual problems experienced with everyday tasks and while driving an automobile. Approximately half of the participants also received a comprehensive examination of their visual status in the form of a psychophysically rigorous assessment of their contrast sensitivity function (CSF). Factor analysis of the survey responses revealed that visual problems experienced while driving increased with age. The emergence of these age-related difficulties occurred along five major dimensions: unexpected vehicles in the peripheral field, judgments of vehicle speed, dim instrument panel displays, windshield problems, and the inability to read street signs. These age-related increases in self-reported visual problems were significantly related to concomitant losses in contrast sensitivity at both intermediate and high spatial frequencies. These data point to areas of research which could yield promising benefits for improving real-world visual functioning among older adult populations.

Nighttime conspicuity of highway signs as a function of sign brightness, background complexity and age of observer

The introduction of ultrabright retroreflective materials may provide the opportunity to develop highway signs with improved conspicuity — especially when viewed in highly complex (i.e., “cluttered”) driving environments. In order to investigate this possibility, the glance conspicuity of briefly presented highway signs was examined as a function of sign brightness (bright vs. ultrabright), background scene complexity (low, moderate, high) and age of observer (young vs. old). Glance conspicuity — measured in terms of both reaction time and accuracy — was found to improve as a function of increased sign brightness when viewed against high complexity (but not low complexity) backgrounds. These findings are discussed in terms of their implications for improved design of traffic control devices.

AGE DIFFERENCES IN THE FUNCTIONAL FIELD-OF-VIEW WHILE DRIVING: A PRELIMINARY SIMULATOR-BASED STUDY

This study represents an initial exploration of a new technique developed to permit the assessment of age differences in the “useful field of view” (Ball, et al., 1993) while simultaneously operating a motor vehicle. Due to necessary safety precautions, this novel approach was first evaluated using a simulated rather than a real-world driving context. Data was collected from seventeen young (mean age = 19.8) and eight older (mean age = 72.9) adult volunteers. Preliminary data analyses indicated that the technique was sensitive to “tunnel vision” effects resulting from experimentally induced limitations in the time available to process stimulus target “onset” events in the visual periphery. The magnitude and time-course of these effects differed markedly as a function of the age of the observer. Shortcomings in the current implementation of the technique and planned improvements are also discussed.

Age differences in the legibility of symbol highway signs as a function of luminance and glare level: a preliminary report

Three experiments were conducted to investigate the effects of adult aging upon the legibility of simulated symbol highway signs. Each experiment employed a different set of lighting conditions: (1) daytime luminance, (2) nighttime luminance, and (3) nighttime luminance with glare. Young (ages 18-25) and middle-aged (ages 40-55) observers demonstrated small reductions in legibility when luminance was reduced from daytime to nighttime levels. However, older (ages 65-79) observers demonstrated marked losses in legibility distance with reductions in sign luminance. The introduction of a glare source (equivalent to approaching automobile headlights at 30 m) reduced sign legibility distance for the older observers but had no deleterious effects upon their young and middle-aged counterparts. The relative magnitude of the observed age, luminance and glare effects appeared to be equivalent across all signs examined.

USING THE "BLUR TOLERANCE" TECHNIQUE TO PREDICT AND OPTIMIZE THE LEGIBILITY DISTANCE OF SYMBOL HIGHWAY SIGNS.

This study investigates the hypothesis that variations in symbol sign legibility distance can be accounted for on the basis of a signs dependence upon high spatial frequency contours to convey critical information. Using digital image processing techniques, highway signs were blurred to remove all high spatial frequency information. A blur recognition threshold was established for each experimental sign by sequentially “deblurring” it until the observer could report the critical details defining its recognition criteria. Correlational analyses were then conducted to determine if legibility distance (collected in a previous study) could be predicted from the blur recognition threshold data. A significant correlation was observed between blur recognition threshold and sign legibility distance (r = −0.734, N=12, p < 0.001). That is, symbol signs with high levels of “blur tolerance” could be recognized at significantly greater viewing distances. These results support the application of new computer-assisted “recursive-blur” design techniques to optimize the effectiveness of symbol highway signs and related visual stimuli (see Schieber, Kline and Dewar, 1994).

Evaluation of the Visual Demands of Digital Billboards Using a Hybrid Driving Simulator

Digital billboards (DBBs) are designed to present a virtually limitless stream of information intended to acquire the attention of passing motorists. Unfortunately, very little published research has been conducted to examine how much information drivers can extract during these epochs, or how the acquisition of this information impacts driving performance. Large-format signs are difficult to study using conventional driving simulators because their displays lack the spatial resolution needed to adequately render signs at distances greater than 100-ft. The current study used a hybrid video/mechanical driving simulator to overcome such limitations. Lane keeping, eye gaze position and reading performance were monitored while participants read digital billboards displaying 4, 8 and 12 words while traveling at 25 and 50 MPH. Results indicated that drivers gradually drift away from the centerline during the DBB inspection interval, and then execute large / sudden compensatory steering inputs to re-establish their position in the center of the lane after the billboard had been overtaken. Conditions leading to visual processing overload are iden-tified and some preliminary guidelines for the design and placement of roadside DBBs are proposed.

Modeling the Appearance of Fluorescent Colors

The advent of improved durability pigments has resulted in the increased use of fluorescent colored materials in safety and warning applications (e.g., high-priority traffic signs; safety vests). Yet, little is known about the relationship between the visual effectiveness of fluorescent colored materials and their photometric properties. Archival data sets were reanalyzed to assess the appropriateness of an elegant psychophysical model of the appearance of fluorescent colors first introduced by Schultze (1953). The results indicated that the expression Y/MacAdam Limit (x,y) provided an excellent prediction of the suprathreshold appearance of fluorescent color (x,y); where (x,y) represented the color of the test stimulus in 1931 CIE chromaticity coordinates. These findings have important implications for design using fluorescent colors and may also contribute significantly to our understanding of related color phenomena.