Age-related differences in collision detection during deceleration

Age-Related Changes in the Utilization of Visual Information for Collision Prediction: A Study Using an Affordance-Based Model

The ability to predict collisions with moving objects deteriorates with aging. We followed the affordance-based model to identify optical variables that older adults had difficulty using for collision prediction. We reproduced a modified version of the interception task used in Steinmetz (Steinmetz, Layton, Powell, & Fajen, 2020, "Affordance-based versus current - future accounts of choosing whether to pursue or abandon the chase of a moving target," Journal of Vision, 20(3), 8) in a virtual reality (VR) environment and newly introduced perturbation for each of three optical variables (vertical and horizontal expansions of a moving object and the bearing angle produced between participants and a moving object). We expected that perturbation would negatively affect the performance only for those who rely on the optical variable to perform the interception task effectively. We tested 18 older and 15 younger adults and showed that older participants were not negatively affected by the perturbation for the vertical and horizontal expansion of a moving object, while they showed decreased performance when the perturbation was introduced with a bearing angle. These findings suggest that predicting collisions with moving objects deteriorates with aging because the perception of object expansion is impaired with aging.

Age-related decline in motion contrast sensitivity due to lower absorption rate of cones and calculation efficiency

Motion perception is affected by healthy aging, which impairs the ability of older adults to perform some daily activities such as driving. The current study investigated the underlying causes of age-related motion contrast sensitivity losses by using an equivalent noise paradigm to decompose motion contrast sensitivity into calculation efficiency, the temporal modulation transfer function (i.e., temporal blur) and 3 sources of internal noise: stochastic absorption of photons by photoreceptors (i.e., photon noise), neural noise occurring at the retinal level (i.e., early noise) and at the cortical level (i.e., late noise). These sources of internal noise can be disentangled because there impacts on motion contrast sensitivity vary differently as a function of luminance intensity. The impact of healthy aging on these factors was evaluated by measuring motion contrast sensitivity of young and older healthy adults at different luminance intensities, temporal frequencies and with/without external noise. The older adults were found to have higher photon noise, which suggests a lower photon absorption rate of cones. When roughly equating the amount of photons being absorbed by the photoreceptors, older adults had lower calculation efficiencies, but no significant aging effect was found on temporal modulation transfer function, early noise and late noise.

Older Drivers and Driving Cessation

Driving is a complex and valued instrumental activity of daily living, which is associated with a person's freedom, independence and autonomy. With an ageing population and various cohort effects, the number of older drivers is increasing at a nearly exponential rate. While drivers over the age of 65 years have attracted media and research attention because of accident statistics, research has also begun to focus on the outcomes for older people giving up driving.

The outcomes of older people driving or giving up driving need to be considered by occupational therapists because of the potential impact on quality of life, life roles, independence and safety. Occupational therapists must be aware of legislation pertaining to older drivers and health professionals, although this is complicated by the fact that it differs between and within countries. This literature review aims to investigate the issues associated with older drivers and with driving cessation and the implications for occupational therapists.

Errors in motion processing amongst older drivers may increase accident risk

Accident statistics highlight that older drivers are more frequently involved in right-of-way collisions than younger drivers. Accurately gauging vehicle speed is critical for judgement of when to pull out from a junction safely in front of oncoming traffic. We used psychophysical methods to measure drivers' ability to discriminate between different rates of looming presented by vehicles approaching at different speeds. We demonstrate that sensitivity to approach speed reduces by between 2.8 and 3.4 mph, dependent upon vehicle type, for every decade that age increases. We show that perceptual limitations for drivers over the age of 75 years can lead to a 50% reduction in time available to perform traffic manoeuvres, which may contribute in part to their overrepresentation in casualty statistics at junction. Results are discussed in terms of implications for road safety policy.

Aging and detection of collision events on curved trajectories

In the current study we examined age-related differences in the detection of collision events on a curved trajectory. Observers were presented with displays simulating an approaching object moving at a constant speed that was either on a collision or a non-collision path. The object disappeared before reaching the observer, and the task was to determine whether the object was on a collision path. In a series of three experiments, we manipulated the motion trajectory of the object (linear or curved), time-to-contact (TTC), and radius of the curvature. We found decreased performance with older as compared to younger observers when the object was traveling on a linear trajectory at long TTC. However, there was no age-related decrement in detecting a collision when the object was traveling on a curved trajectory. These results indicate a similar ability for older and younger observers in detecting collisions on a curved trajectory.

Aging and the detection of imminent collisions under simulated fog conditions

The present study examined age-related differences in collision detection performance when contrast of the driving scene was reduced by simulated fog. Older and younger drivers were presented with a collision detection scenario in a simulator in which an object moved at a constant speed on a linear trajectory towards the driver. Drivers were shown part of the motion path of an approaching object that would eventually either collide with or pass by the driver and were required to determine whether or not the object would collide with the driver. Driver motion was either stationary or moving along a linear path down the roadway. A no fog condition and three different levels of fog were examined. Detection performance decreased when dense fog was simulated for older but not for younger observers. An age-related decrement was also found with shorter display durations (longer time to contact). When the vehicle was moving decrements in performance were observed for both younger and older drivers. These results suggest that under inclement weather conditions with reduced visibility, such as fog, older drivers may have an increased crash risk due to a decreased ability to detect impending collision events.

Aging and vision: changes in function and performance from optics to perception

Age-related declines in vision can have a major impact on the health and well-being of an older population. A review of research on aging and vision indicates that these declines occur at multiple levels of the visual system including optics, sensory processing, and perceptual processing and are not likely due to a systemic change in brain function (e.g., generalized slowing; common cause hypothesis) as a result of normal aging. In addition, declines in sensory and perceptual processing are not due to low-level explanations such as the amount of light that reaches the retina. Declines in visual performance are due to a variety of distinct factors that include spatial integration and difficulty in processing visual information in the presence of noise. Neurophysiological studies suggest that processing declines may be due in part to changes in cortical inhibition mediated by changes in the level of neurotransmitters associated with inhibition. Despite the widespread declines in function with normal aging, recent research suggests that perceptual learning can be used to dramatically improve visual function for older individuals. This research suggests a high degree of plasticity of the visual system among older populations and suggests that perceptual learning is an important tool for the recovery of age-related declines in vision. WIREs Cogn Sci 2012, 3:403-410. doi: 10.1002/wcs.1167 For further resources related to this article, please visit the WIREs website.

Aging and vision

Given the increasing size of the older adult population in many countries, there is a pressing need to identify the nature of aging-related vision impairments, their underlying mechanisms, and how they impact older adults' performance of everyday visual tasks. The results of this research can then be used to develop and evaluate interventions to slow or reverse aging-related declines in vision, thereby improving quality of life. Here we summarize salient developments in research on aging and vision over the past 25 years, focusing on spatial contrast sensitivity, vision under low luminance, temporal sensitivity and motion perception, and visual processing speed.

Representational momentum in older adults

Humans have a tendency to perceive motion even in static images that simply "imply" movement. This tendency is so strong that our memory for actions depicted in static images is distorted in the direction of implied motion - a phenomenon known as representational momentum (RM). In the present study, we created an RM display depicting a pattern of implied (clockwise) rotation of a rectangle. Young adults viewers' memory of the final position of the test rectangle was biased in the direction of continuing rotation, but older adults did not show a similar memory bias. We discuss several possible explanations for this group difference, but argue that the failure of older adults to shown an RM effect most likely reflects age-related changes in areas of the brain involved in processing real and implied motion.

Detection of imminent collisions by drivers with Alzheimer's disease and Parkinson's disease: a preliminary study

The aim of this study was to assess whether patients with neurodegenerative disease, namely Alzheimer's disease (AD) and Parkinson's disease (PD), differed from age-matched, neurologically normal comparison participants in their ability to detect impending collisions. Six AD patients and 8 PD patients, together comprising the neurodegenerative disease group, and 18 comparison participants completed a collision detection simulation task where they must judge whether approaching objects would collide with them or pass by them. The neurodegenerative disease group was less sensitive in detecting collisions than the comparison group, and sensitivity worsened with increasing number of objects in the display and increasing time to contact of those objects. Poor performance on tests of cognition and visual attention were associated with poor collision detection sensitivity. The results of this study indicate that neurodegenerative disease impairs the ability to accurately detect impending collisions and that these decrements are likely the combined result of visual and cognitive disturbances related to disease status.

Effects of aging on biological motion discrimination

Previous studies have shown that older subjects have difficulties discriminating the walking direction of point-light walkers. In two experiments, we investigated the underlying cause in further detail. In Experiment 1, subjects had to discriminate the walking direction of upright and inverted point-light walkers in a cloud of randomly moving dots. In general, older subjects performed less accurately and showed an increased inversion effect. Nevertheless, they were as accurate as young subjects for upright walkers during training, in which no noise was added to the display. These results indicate that older subjects are less able to extract relevant information from noisy displays. In Experiment 2, subjects discriminated the walking direction of scrambled walkers that primarily contained local motion information, random-position walkers that primarily contained global form information, and normal point-light walkers that contained both kinds of information. Both age groups performed at chance when no global form information was present in the display but were equally accurate for walkers that only contained global form information. However, when both local motion and global form information were present in the display, older subjects were less accurate then younger subjects. Older subjects again exhibited an increased inversion effect. These results indicate that both older and younger subjects rely more on global form than local motion to discriminate the direction of point-light walkers. Also, older subjects seem to have difficulties integrating global form and local motion information as efficiently as younger subjects.

Mental workload when driving in a simulator: effects of age and driving complexity

Driving errors for older drivers may result from a higher momentary mental workload resulting from complex driving situations, such as intersections. The present study examined if the mental workload of young and older active drivers vary with the difficulty of the driving context. We adopted the probe reaction time (RT) technique to measure the workload while driving in a simulator. The technique provided clear instructions about the primary (driving) and secondary (RT) tasks. To avoid structural interference, the secondary task consisted of responding as rapidly as possible with a vocal response ("top") to an auditory stimulus. Participants drove through a continuous 26.4-km scenario including rural and urban sections and probes (stimuli) were given in a baseline static condition and in three different driving contexts embedded into the overall driving scenario. Specifically, stimuli were given randomly when (a) driving on straight roads at a constant speed, (b) approaching intersections for which the driver had to stop the car, and (c) when overtaking a slower vehicle. Unless a driving error was made, drivers did not need any emergency responses. Reaction time was defined as the temporal interval between the auditory stimulus and the onset of the corresponding verbal response detected from the analog signal of a piezo-electric microphone fixed on a headset (ms accuracy). Baseline RTs were similar for both groups. Both groups showed longer RTs when driving and RTs increased as the complexity of the driving contexts increased (driving straights, intersections, overtaking maneuvers). Compared to younger drivers, however, older drivers showed longer RTs for all driving contexts and the most complex driving context (overtaking maneuvers) yielded a disproportionate increase. In conclusion, driving leads to a greater mental workload for the older drivers than for the younger drivers and this effect was exacerbated by the more complex driving context (overtaking maneuvers).

Detection of collision events on curved trajectories: optical information from invariant rate-of-bearing change

Previous research (Andersen & Kim, 2001) has shown that a linear trajectory collision event (i.e., a collision between a moving object and an observer) is specified by objects that expand and maintain a constant bearing (the object location remains constant in the visual field). In the present study, we examined the optical information for detecting a collision event when the trajectory was of constant curvature. Under these conditions, a collision event is specified by expansion of an object and a constant rate-of-bearing change. Three experiments were conducted in which trajectory curvature and display duration were varied while time to contact, speed, and initial image position of the collision objects were maintained. The results indicated that collision detection performance decreased with an increase in trajectory curvature and decreased with a decrease in display duration, especially for highly curved trajectories. In Experiment 3, we found that the presentation of a constant rate-of-bearing change in noncollision stimuli resulted in an increase in the false alarm rate. These results demonstrate that observers can detect collision events on curved trajectories and that observers utilize bearing change information.

Aging and visual processing: declines in spatial not temporal integration

Age-related declines in vision are well documented in the literature. In the present study we examined whether changes in spatial or temporal integration contribute to this decline. Younger (mean age of 21) and older (mean age of 745) subjects were asked to identify 2D shapes based on kinetic occlusion information---the accretion and deletion of texture during motion. The results of the first experiment indicated age-related decrements in spatial but not temporal integration. In the second experiment we manipulated the lifetime of motion stimuli to more directly examine temporal integration. The results indicated no differential effect of age on temporal integration. The results considered together suggest age related changes in recovering 2D shape from occlusion are the result of spatial but not temporal integration. Age-related changes in neural inhibition and ACh for regulating spatial integration are proposed as possible mechanisms for this decline.

Aging and the detection of observer and moving object collisions

The authors examined age-related differences in the detection of collision events. Older and younger observers were presented with displays simulating approaching objects that would either collide or pass by the observer. In 4 experiments, the authors found that older observers, as compared with younger observers, had less sensitivity in detecting collisions with an increase in speed, at shorter display durations, and with longer time-to-contact conditions. Older observers also had greater difficulty when the scenario simulated observer motion, suggesting that older observers have difficulty discriminating object motion expansion from background expansion from observer motion. The results of these studies support the expansion sensitivity hypothesis-that age-related decrements in detecting collision events involving moving objects are the result of a decreased sensitivity to recover expansion information.

Motion extrapolation of car-following scenes in younger and older drivers

OBJECTIVE

The objective was to determine whether distortions occur in motion extrapolation of car-following scenes in younger and older drivers.

BACKGROUND

Drivers cannot see an entire traffic scene clearly with one glance. They must extrapolate the motion of surrounding vehicles while scanning other parts of the scene. Further, abilities relevant to motion extrapolation decline with age. Thus, it is important to evaluate age differences in motion extrapolation.

METHOD

Displays simulated car-following scenes. After an interruption, the scene reappeared at the correct position in its trajectory or at a position that was more advanced or less advanced than the correct position. Drivers reported whether the scene reappeared at the correct position.

RESULTS

When the virtual self moved faster than the lead car, older drivers' judgments were biased toward less advanced reappearance positions. Younger drivers' judgments were biased toward more advanced positions. The implication is that older drivers extrapolated the motion slower than did younger drivers.

CONCLUSION

Distortions occurred in motion extrapolation of car-following scenes, and age differences occurred in such distortions.

APPLICATION

Potential applications of this research include traffic safety. Age differences in motion extrapolation are useful to consider in differential accident patterns of younger and older drivers. Future research should investigate the relationship between accidents and the ability to extrapolate motion, particularly during driver distractions.

Eye fixation scanpaths of younger and older drivers in a hazard perception task

Our previous research has shown that observing patterns of eye fixations is a successful method of establishing differences in underlying cognitive processes between groups of drivers. Eye movements recorded from drivers in a laboratory while they watch film clips recorded from a driver's perspective can be used to identify scanpaths and search patterns that reveal ability differences. In the present study 12 older subjects (60-75 years) and 12 younger subjects (30-45 years) watched clips for potential hazards such as other road users appearing on an intersecting trajectory. Acuity and visual field differences between the two groups were eliminated through screening, so that only age-related differences would emerge. Eye fixations were analysed on a frame-by-frame basis to generate sequences of codes representing the location and object of the viewer's interest, before and during the appearance of a hazard. These codes were analysed for the existence of two fixation scanpaths using Markov Matrices. Unique scanpaths were identified for each group of drivers before and during the hazard. Evidence from the inspection of different objects and from the spread of the search indicated that both groups of driver were sensitive to attentional capture by the appearance of the hazard. Detection of the hazards - both speed and accuracy - was similar for older and younger drivers, although the older drivers perceived the films as being more hazardous in general. There is little evidence in this study of an age-related decline in the search of the scene when detecting hazards.

Using a driving simulator to identify older drivers at inflated risk of motor vehicle crashes

PROBLEM

To develop appropriate assessment criteria to measure the performance of older drivers using an interactive PC-based driving simulator, and to determine which measures were associated with the occurrence of motor-vehicle crash.

METHOD

One hundred and twenty-nine older drivers residing in a metropolitan city volunteered to participate in this retrospective cohort study. Using the driving simulator, appropriate driving tasks were devised to test the older drivers, whose performances were assessed by 10 reliable assessment criteria. Logistic regression analysis was then undertaken to determine those criteria that influence the self-reported crash outcome.

RESULTS

As expected, driving skill of older drivers was found to decline with age. Over 60% of the sample participants reported having at least one motor-vehicle crash during the past year. Adjusting for age in a logistic regression analysis, the cognitive abilities associated with the crash occurrence were working memory, decision making under pressure of time, and confidence in driving at high speed.

SUMMARY

The findings of this retrospective study indicated those individuals at inflated risk of vehicle crashes could be identified using the PC-based interactive driving simulator. Prospective studies need to be undertaken to determine whether the driving simulator can predict future crash events.

IMPACT ON INDUSTRY

This study demonstrated an economical driving simulator approach to screen out problematic or unsafe older drivers before a more detailed but expensive road test is considered.