Mathematical Modeling of Age Differences in Hierarchical Navigation Systems

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Wayne State UniversityInstitute of Gerontology

Panayiotis ZaphirisIndustrial and Manufacturing Engineering Dept.

Institute of GerontologyWayne State University

Detroit, MI

Older Adults and the World Wide Web

Know the User

• Seniors are the fastest growing group on the internet.

• 25% of seniors with computers are online

• 70% are using their computers daily [Morris, D. C. (1996)].

• Important to develop age-friendly web pages.

• The World Wide Web is not (should not be) just for young people !

Today’s Presentation

• What attracts elders to the internet ?

• What changes with aging ?

• Web Design and Aging - Guidelines ?

• Search Engines (case study)

• Depth Vs Breadth (an other issue)

What Attracts Elders to the Internet?

• Connectivity– Chat online with

friends and family– Express their opinions– Feel less socially

isolated– Start second careers– Research health issues

What Attracts Elders to the Internet?

• Self-paced Environment

• Dynamic and Interactive– The web can become a means of socializing and

maintaining contact with the outside world (especially for older adults suffering from loneliness, feelings of isolation and depression)

• Anonymity

What changes with Aging?

• Vision– Size of field of vision may diminish– Difficulty in following fast moving objects.– Many experience short-sightedness – Changes in perception of color

• Cognitive– Some older adults have slower response times– May have difficulty performing multiple tasks

(especially new ones)– Less able to ignore irrelevant stimuli (eg.

Banner advertisements)– Decline in spatial abilities.

• Hearing– Hearing loss or diminishment.– Problems hearing high frequencies and in

distinguishing speech.

• Motor Skills– Small movements or finite mouse control can be

troublesome (especially for people suffering with arthritis).

Guidelines - Layout

• Layout– Large areas of white space and small blocks of

text increase readability.– Keep layouts and the interface similar from page

to page and make sure all the important navigation elements stay consistent.

– Don’t limit window size of your pages

Guidelines - Style

• Style– Choose fonts based on their legibility– Avoid colors that are exceptionally bright or

vibrant.– Animation or any quickly flashing or blinking

elements or banners are highly distracting.– Make all graphical links and buttons large and

easy to click on.

Guidelines - Color• Color

– Use color effectively– Pick colors from opposite sides of the color

wheel– Avoid combinations of blue - yellow and red -

green.

Guidelines

• Contrast– Greatest contrast exists between black & white.– View your pages on a black and white monitor

• Font– Larger type is easier to read. Twelve to fourteen

points is good font size for seniors.– Don’t limit ability to set his/her own font.

• Accessibility

Depth Vs Breadth

• Depth vs Breadth trade-off is a hot topic in menu selection.

• Depth seems to be the driving force in reaction time.

• Previous research has shown that previous studies on menu selection apply to web hierarchies.

Previous Research

• Analytical models– Lee and MacGregor (1985)– Paap and Roske-Hofstrand (1986)

• Empirical studies– Numerous menu related breadth vs depth– Very few web related (but replicate menu related

studies).

Lee MacGregor modelFor Exhaustive Search: TE

b d d b t k c( )

For Self-Terminating Search TSb d d

b 1( ) t

TE and TS represent task completion timesd = depth of link/menu hierarchyb = breath of link/menu hierarchyt = time to read or process one optionk = human response timec = computer response time

Proposed Modified Model

For Exhaustive Search - Aging: TEAb d d b a1 t a2 k c( )

For Self-Terminating Search - Aging: TSAb d d

b 1( ) a1 t

2a2 k c

Where a1 and a2 are age related parameters.

Sample contour plots•Young users with t = 0.25, k = 0.5, c = 0.5•TE = Exhaustive, TS = Self - terminating searching

2 4 6 8 10

Sample contour plots•Seniors with t = 0.25, k = 0.5, c = 0.5•TEA = Exhaustive, TSA = Self - terminating searching (aging)TSA

b d db 1( ) a1 t

2a2 k c

2 4 6 8 10

28.205

TEAb 5

TSAb 5

1 1.5 2 2.5 3 3.5 4 4.5 5 5.5 6 6.5 7 7.5 8 8.5 9 9.5 108

30Plot of Times versus breadth

breadth

39.385

TEA5 d

TSA5 d

1 1.5 2 2.5 3 3.5 4 4.5 5 5.5 6 6.5 7 7.5 8 8.5 9 9.5 100

40Plot of Times versus depth

Optimization Results

k tE EA S SA E EA S SA

0.5 0.25 6 6 8 8 7 6 10 100.5 .5 4 4 6 6 5 5 7 70.5 1 4 4 5 5 4 4 6 60.5 2 3 3 4 4 3 3 5 51 .25 7 7 10 10 8 8 12 121 .5 5 5 7 7 6 6 8 81 1 4 4 6 6 4 4 6 61 2 3 3 5 5 4 4 5 5

c=0.5 c=1.0

Results being the optimum number of items per screen. E = Exhaustive, S = Self terminating, EA = Exhaustive aging, SA = Self terminating aging.

Further research

• Structural Equation Modeling to more accurate measure the aging factor in information retrieval and searching on the web.

• Usability testing and participant observation.

• Surveys.

Conclusions

• Sensitivity to age related differences and web design.

• Web should be as universal and accessible as possible for people of all ages.

Mathematical Modeling of Age Differences in Hierarchical Navigation Systems

Technology