How Age Affects User Performance on the Web

Why HID Considers Research with Older Adults an Important Focus

As indicated in the Year 2000 United States Census, there are 35 million people age 65 or older in the U.S., a 12% increase over the previous U.S. Census (1990). Among the older population, those 75 years and older showed a 23% increase and those 85 and older showed the highest percentage increase at 38%.

What this means in a practical sense is that there is an increasing number of older adults in the U.S., especially those over the age of 75. This also means that there is an increasing number of senior citizens using the Web. According to Nielsen (2002), there are an estimated 4.2 million Internet users over the age of 65 in the U.S. To better understand and meet the needs of this important and growing demographic, Human Interface Design (HID) conducted some research.

Our Research

During March and April of 2002, we conducted an extensive usability study that included 27 external (non-Fidelity) participants ranging in age from 20 to 82. The primary goal of this study was to learn whether older adults interact differently with the Web than younger adults do. A secondary goal was to learn whether changing the size of text on the screen would affect performance and whether this differed with age.

The participants were recruited from three age groups (Under 35, 35-64, 65+) with nine in each group, and their level of PC and Web experience was balanced across groups. The study consisted of completing tasks on a prototype version of a retirement benefits web site that had been modified to allow for font-scaling and variable-width pages.

Participants used three versions of the prototype, each differing only by the size of the text displayed. (The font size was changed using the View/Text Size function of Internet Explorer.) Participants completed 15 tasks in all, 5 with each of the three font sizes.

What We Learned: A Summary of Results

We learned that older users (55 years or older) had significantly more difficulty using the Web site as compared to younger users. They completed fewer tasks successfully and took longer to complete each task. (See Table 1.) When task success and task duration were standardized and combined to compute an overall performance score, older users demonstrated that they were had more than twice the difficulty of their younger counterparts. (Keep in mind that we controlled for level of PC and Web experience.) These results are quite similar to a recent publication by the Nielsen/Norman Group on "Web Usability for Senior Citizens."

Interestingly, text size did not have a significant effect on performance for any age group, though older users were more likely to prefer the largest text size. So, even though it has been widely believed that a major reason older adults have difficulty using the Web is partly due to their inability to read small text, our study has demonstrated that simply providing very large text to older adults does not improve their overall performance.

Performance and Age

The older users were, the fewer tasks they completed successfully and the longer they took to complete each task. Similarly, users with less experience were more likely to have longer task duration times. Both age and experience correlated to overall performance, with age showing the strongest correlation.

By standardizing the task duration and success rates and then combining them, an overall performance score (z-score) was calculated for each participant. Using this combined performance measure, overall performance and age were strongly correlated (r = - 0.60). The older people were, the lower their overall performance. (See Figure 1.)

Performance and Web/PC Experience

Task duration and experience were also strongly correlated (r = - 0.60). (See Figure 2.) The more experienced people were, the less time they took to complete each task. Task success and experience were not correlated (r = 0.22).

Age and Overall Text Size Preference

Though text size did not affect the performance for any age group, there was a difference in preference ratings between age groups. (See Figure 3.) A larger percentage of older adults were more likely to prefer the largest text than younger adults (p<.01).

Our Observations of Older Users

During the usability sessions, extensive observational notes were recorded in an attempt to understand the behavioral differences that might exist between younger and older adults. We observed the following notable differences in how older participants interacted with the Web site.

• Older Users Have a More Cautious User Interaction Approach
  Older users were far more cautious in everything they did on the Web, including clicking on links. They spent more time reading information before clicking and even pondering the pros and cons of clicking before attempting to click a link. We call this behavior "cautious clickers."
  
  Whereas younger users click rather haphazardly in their attempts to find information, older users tended to be very cautious with their click behavior, almost as though clicking represented an action that they may not be able to reverse. We analyzed click data for a random sampling of the tasks and found that older adults averaged significantly fewer clicks per minute than younger adults. (See Figure 4.)
  
  Figure 4. Average Number of Clicks per Minute.
• Older Users Spend More Time Reading Text and Instructions
  Older users tended to read more text and often read the entire text on a screen, especially when they were being asked to input information. They often read entire pages of legal information that younger users virtually ignored.
• Older Users Have Difficulty Reading Text on Screen
  Many of the older users had difficulty reading the text on the screen, particularly when using the smallest text size version. We observed many leaning forward attempting to read the text better.
• Older Users Are More Likely to Prefer Larger Text Size
  Since a larger percentage of older adults were more likely to prefer the largest text-size version than younger adults (p<.01), we recommend a design that uses scalable fonts (fonts that the user can increase and decrease in size).
• Older Users Click on Non-Links More Often
  Many of the older users repeatedly clicked on items that were not links, including table headings, bullets, icons, and just plain text. They did not immediately view underlining, or even blue underlining, as links. Their strategy seemed to be to click on any item that seemed to meet their expectations for whatever target they were seeking.
  
  For example, when they were trying to change something in a retirement account, they often clicked on a heading in the left navigation that was termed "Account Management" simply because they were trying to "manage their account." When we analyzed the click data, we also recorded the number and types of clicks. We found that older users were significantly more likely to click on non-links (p<.01). (See Figure 5.)
  
  Figure 5. Average Number of Clicks per Task by Click Type.
• Older Users Have Trouble with Window Management and Scrolling
  In secondary pop-up windows that forced horizontal scrolling, older users did not notice the horizontal scroll bar and often never saw the information on the right side on the screen. Many older users did not know how to minimize or maximize their windows or how to scroll horizontally. When they did notice the horizontal scrolling, they often commented that this was a poor design, still not knowing how to maximize their windows.
• Older Users Have Difficulty Understanding their Location or Path
  Older users were often confused as to where they were within the context of the Web site. Several times they clicked on a link in the left navigation when they were already on that page. Many older users failed to see the connection between content on the home page and content within the site. In general, older users seemed to have less understanding of the site organization or structure.
• Older Users Were Often Confused with Jargon and Technical Terms
  Older users often did not know terms with which younger users were all familiar. Some of these were benefits industry terms such as "HR" and others were financial terms like "brokerage."

Our Next Steps

The main finding of our study was that older users had more difficulty completing tasks on the Web. They completed fewer tasks successfully and took longer to complete these tasks. This finding is not so surprising and has been supported by the recent Pernice Coyne and Nielsen (2002) study of usability for senior citizens.

Now that there is strong empirical evidence to show that older users do have moderate difficulty interacting with the Web, the more important questions to answer are as follows:

• What specific behaviors of older users are contributing to this poorer performance?
• What specific aspects of Web design are causing older users the most difficulty?

Only by answering these two questions can we begin to improve Web usability for older adults. If we understand their unique behaviors and those specific design aspects that cause them difficulty, we can modify Web design to accommodate their unique requirements.

For Phase 2 of this study, we plan to redesign the prototype in a way that addresses each of the usability problems encountered by older adults in Phase I of this study. We will repeat the exact study using the redesigned site and learn whether the changes in design help older adults while not compromising performance for younger adults.

For More Information

• U.S. Census Bureau, U.S. Census 2000: http://www.census.gov/main/www/cen2000.html