Biomedical subjects

Geoffrey Ho

Publications and source records attributed to Geoffrey Ho.

6 recordsLinked to original sources

PubMed2006

The Independent LifeStyle Assistant: lessons learned.

The Independent LifeStyle Assistant (I.L.S.A.) is an agent-based monitoring and support system to help elderly people live longer in their homes by reducing caregiver burden. I.L.S.A. is a multiagent system that incorporates a unified sensing model, situation assessments, response planning, real-time responses, and machine learning. This paper describes the six-month study of the system we fielded in elders' homes and the major lessons we learned during development.

Activities of Daily Living↗

PubMed2004

Age differences in feature selection in triple conjunction search.

Younger and older participants were trained in a triple conjunction visual search task to examine age differences in the development of proficient performance. For the first 8 days, participants searched for a target defined by its contrast polarity, shape, and orientation. On Days 9 through 16, the target identity was switched to one defined by opposing feature values. On Day 17, the target was returned to the original feature values. Results indicated that, after training, younger adults reduced their display size effects more than elderly adults. Disruption occurred after the first but not after the second transfer. However, each time the target was switched, there were no age differences in disruption. Eye movement data suggest that older adults use a similar feature selection strategy as younger adults but may be more susceptible to distraction. The results are discussed in terms of current models of attention and search.

Adult↗

PubMed2004

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.

Adult↗

PubMed2004

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.

Accidents, Traffic↗

PubMed2003

Plasticity of feature-based selection in triple-conjunction search.

Two experiments examined the disruption of feature-based selection in triple-conjunction search at multiple target transfers. In Experiment 1, after 10 training sessions, a new target possessing previous distractor features was introduced. This produced disruption in RT and fixation number, but no disruption in feature-based selection. Specifically, there was a tendency to fixate objects sharing the target's contrast polarity and shape and this did not change even upon transfer to the new target. In Experiment 2, 30 training sessions were provided with three target transfers. At the first transfer, the results replicated Experiment 1. Subsequent transfers did not produce disruption on any measure. These findings are discussed in terms of strength theory, Guided Search, rule-based approaches to perceptual learning, and the area activation model.

Adult↗

PubMed2002

Age, skill transfer, and conjunction search.

Ten younger and ten older adults were provided with 16 sessions of conjunction search under consistent mapping, where target and distractors remain constant in identity. The target and one distractor were reversed after every fourth session. After the first four training sessions, on target-present trials, display size slopes were near zero for both age groups. However, on target-absent trials, older adults continued to show significantly larger display size effects than younger adults. There were no systematic age differences in either the probability of fixating objects that possess the target's features or in the amount of disruption at any reversal. Thus, although older adults exhibited more conservative criteria in visual search, they developed proficient and flexible search skill to the same degree as their younger counterparts. These data have implications for models of visual attention, skill acquisition, and cognitive aging.

Adult↗