The Effect of Time Constraints on Older and Younger Driver Decisions to Turn at Intersections Using a Modified Change Blindness Paradigm

After age 75, the risk of intersection accident involvement for older drivers increases for most intersection maneuvers. Failure to yield right-of-way and violation of traffic controls are common citations. Previous research has argued that age-related declines in attentional breadth and switching can discriminate between those who are and are not more likely to be in an accident. The present study examined the effect of time constraints on older and younger driver intersection decisions. It was expected that less time to decide, process and act upon intersection decisions would adversely affect older drivers more so than younger drivers. The change blindness or flicker paradigm was modified to address these questions (see, e.g., Rensink, et al., 1997). Typically, an image (A) is alternated with a modified image (A’) each for a short duration (250 ms) with a blank field or mask (80 ms) between A and A’. In the present study, a focus screen (or prime) that indicated the expected direction of travel (i.e., left, right, or straight) was added prior to the alternation of images. Forty-eight images were selected from 2500 intersection approaches in Calgary, Winnipeg and Montreal that were filmed using a digital camera during the day. Photoshop was used to create the A’ images by manipulating a variety of elements including pedestrians, vehicles, signs, and signals. The goal of the participant was to decide if the indicated direction of travel in the pair of intersection images was safe (press accelerator) or not (press brake). Sixteen younger (M = 22.3) and 16 older drivers (M = 73.6) drivers were screened for visual acuity, contrast sensitivity, and medication use. Length of image alternation was the primary independent variable (4 and 8 s). As expected, older drivers were more likely to miss intersection changes at shorter exposure durations than younger drivers. A number of qualitative probes were also collected that clearly illustrate the contextual demands of intersections on attention. The implications of the results for intersection design and older driver selective attention are discussed

Age-related decline of peripheral visual processing: the role of eye movements

Earlier work suggests that the area of space from which useful visual information can be extracted (useful field of view, UFoV) shrinks in old age. We investigated whether this shrinkage, documented previously with a visual search task, extends to a bimanual tracking task. Young and elderly subjects executed two concurrent tracking tasks with their right and left arms. The separation between tracking displays varied from 3 to 35 cm. Subjects were asked to fixate straight ahead (condition FIX) or were free to move their eyes (condition FREE). Eye position was registered. In FREE, young subjects tracked equally well at all display separations. Elderly subjects produced higher tracking errors, and the difference between age groups increased with display separation. Eye movements were comparable across age groups. In FIX, elderly and young subjects tracked less well at large display separations. Seniors again produced higher tracking errors in FIX, but the difference between age groups did not increase reliably with display separation. However, older subjects produced a substantial number of illicit saccades, and when the effect of those saccades was factored out, the difference between young and older subjects’ tracking did increase significantly with display separation in FIX. We conclude that the age-related shrinkage of UFoV, previously documented with a visual search task, is observable with a manual tracking task as well. Older subjects seem to partly compensate their deficit by illicit saccades. Since the deficit is similar in both conditions, it may be located downstream from the convergence of retinal and oculomotor signals

Reduced sensitivity for visual textures affects judgments of shape-from-shading and step climbing behaviour in older adults

Falls on stairs are a major hazard for older adults. Visual decline in normal aging can affect step climbing ability, altering gait and reducing toe clearance. Here we show that a loss of fine-grained visual information associated with age can affect the perception of surface undulations in patterned surfaces. We go on to show that such cues affect the limb trajectories of young adults, but due to their lack of sensitivity, not that of older adults. Interestingly neither the perceived height of a step nor conscious awareness are altered by our visual manipulation but stepping behaviour is: suggesting that the influence of shape perception on stepping behaviour is via the unconscious, action-centred, dorsal visual pathway

How useful are volunteers for visual biodiversity surveys? An evaluation of skill level and group size during a conservation expedition

The ability of volunteers to undertake different tasks and accurately collect data is critical for the success of many conservation projects. In this study, a simulated herpetofauna visual encounter survey was used to compare the detection and distance estimation accuracy of volunteers and more experienced observers. Experience had a positive effect on individual detection accuracy. However, lower detection performance of less experienced volunteers was not found in the group data, with larger groups being more successful overall, suggesting that working in groups facilitates detection accuracy of those with less experience. This study supports the idea that by optimizing survey protocols according to the available resources (time and volunteer numbers), the sampling efficiency of monitoring programs can be improved and that non-expert volunteers can provide valuable contributions to visual encounter-based biodiversity surveys. Recommendations are made for the improvement of survey methodology involving non-expert volunteers