Geoffrey Ho

Visual search for traffic signs: the effects of clutter, luminance, and aging.

Latency and eye movement measures were used to examine the effects of aging, clutter, and luminance on visual search for traffic signs embedded in digitized images of driving scenes. Initially 14 older and 14 younger observers classified daytime and nighttime traffic scenes as containing low or high amounts of clutter. Next, an independent sample of 14 younger and 14 older participants searched for traffic signs contained within these scenes. Errors were more common among the elderly. Search efficiency declined with increased clutter and with aging. However, relative to the young, older adults did not suffer disproportionately as a result of increased clutter. The methods developed might be profitably employed to assess sign conspicuity and sign acquisition during driving.

Age differences in visual search for traffic signs during a simulated conversation.

The effects of divided attention were examined in younger adults (M = 23 years) and older adults (M = 64 years) who searched for traffic signs in digitized images of traffic scenes. Sign search was executed under single-task and dual-task conditions in scenes containing either small or large amounts of visual clutter. For both age groups, clutter and the secondary task had additive effects on search accuracy, speed, and oculomotor involvement. Compared with the younger adults, older adults were less accurate, especially with high-clutter scenes, were slower to decide that a target sign was not present, and exhibited a marginally greater divided-attention effect on reaction times. They exhibited longer fixations in the divided-attention condition, in which they also showed a disproportionate reduction in recognition memory for the content of the secondary task. Actual or potential applications of this research include methods for evaluating the distraction of conversations and safety implications of conversation on visual search behavior.

Age differences in trust and reliance of a medication management system

The present study examined age differences in trust and reliance of an automated decision aid. In Experiment 1, older and younger participants performed a simple mathematical task concurrent with a simulated medication management task. The decision aid was designed to facilitate medication management, but with varying reliability. Trust, self-confidence and usage of the aid were measured. The results indicated that older adults had greater trust in the aid and were less confident in their performance, but they did not calibrate trust differently than younger adults. In Experiment 2, a variant of the same task was used to investigate whether older adults are subject to over-reliance on the automation. Differences in omission and commission errors were examined. The results indicated that older adults were more reliant on the decision aid and committed more automation-related errors. A signal detection analyses indicated that older adults were less sensitive to automation failures. Results are discussed with respect to the perceptual and cognitive factors that influence age differences in the use of fallible automation.

The Context-Aware Pill Bottle and Medication Monitor

The video illustrates and critiques a context-aware pill bottle/stand that reminds the elderly when it is time to take their medication. A medication monitor situated in a caregiver’s home displays awareness information about the elderly user’s medication compliance.

Traffic Sign Conspicuity: The Effects of Clutter, Luminance, and Age

The effects of visual clutter, luminance, and aging on traffic sign conspicuity were examined in two experiments. Experiment 1a evaluated clutter using subjective judgments from 28 older and younger observers. Participants categorized daytime and nighttime traffic scenes into high or low clutter. Using these categorized scenes, in Experiment 1b a new sample of 28 younger and older participants visually searched for traffic signs. Reaction time and eye movement data were analyzed. Results suggested that aging and clutter affect con-spicuity. Moreover, older adults had poorer performance on target-absent trials. No luminance effect or any age by clutter interactions were obtained. Expertise gained through many years of driving may dampen clutter effects experienced by older adults. The nonlinear relationship between fixation frequency and fixation duration is discussed in relation to similar findings in experimental visual search. Results suggest that age differences found in processing simple visual stimuli may not generalize to more naturalistic scenes.

The effects of a simulated cellular phone conversation on search for traffic signs in an elderly sample

The effects of clutter and a simulated cellular telephone conversation on search for traffic signs were investigated using eye movement and reaction time measures. One-half of an elderly sample searched for traffic signs while simultaneously listening to a story, followed by 15 “yes or no” questions. This simulated cellular phone conversation had detrimental effects on reaction time, fixation number and fixation duration. Performance decrements observed might be an indication of the demands cellular telephones have on a drivers processing resources. In addition, these methods could be used to further investigate the safety implementation of using a cellular telephone while driving.

Varied-mapping conjunction search: Evidence for rule-based learning

Five experiments were carried out to examine whether top-down processes can aid search, even when targets and distractors are variably mapped. Experiments 1a and 1b determined that effortless VM search can be obtained in Contrast Polarity X Orientation and Color X Orientation conjunction search when one feature dimension remains consistently mapped across blocks. Experiment 2 showed that efficient VM search is possible when both dimensions are variably mapped. In Experiment 3, efficient VM search was found when target-distractor reversals occurred on a trial-wise basis. Experiments 4 and 5 found that VM search deteriorates when target identity is not known prior to display onset. These studies demonstrate the role of top-down mechanisms in the development of efficient VM search and present several challenges to strength-theoretic views on the mechanisms underlying automaticity.