Below is an excerpt of Chapter 4 from our book. The book is available where fine books are sold or directly from our publisher CRC Press. Until January 31, 2011, you can get 20% off the cover price when you purchase directly from CRC Press using this link and this code: 810DE.
Chapter Contents (excerpt is bolded below)
4.1 How Cognition Changes With Age
4.1.1 Fluid Abilities
220.127.116.11 Perceptual Speed
18.104.22.168 Working Memory Capacity
22.214.171.124.1 Environmental Support
126.96.36.199 Reasoning Ability
188.8.131.52 Spatial Ability
184.108.40.206 Interim Summary of Fluid Abilities
4.1.2 Crystallized Knowledge
220.127.116.11 Verbal Ability
18.104.22.168 Knowledge and Experience
22.214.171.124 Mental Models
126.96.36.199 Interim Summary of Crystallized Intelligence
4.2 In Practice: Organization of Information
4.4.1 Page Navigation vs. Browser Navigation
4.4.2 Previous Knowledge and Browsing/Searching for Information
4.3 General Design Guidelines
4.4 Suggested Readings
188.8.131.52 Reasoning Ability
Reasoning ability is the ability to tackle and understand novel situations. It is the ability that one uses when faced with a new television remote control, visits an unfamiliar website, or tries out a new computer application without reading the manual. Psychologists measure reasoning ability using abstract tests that require test takers to determine logical sequences in patterns. Figure 4.7 illustrates a sample item from such test. The task is to examine the figures on the test to discover the rule that governs the sequence of shapes and then select the correct shape in the sequence. The abstractness of the test is deliberate so that factors such as cultural background or language skill will not interfere with the results.
The link between performance on such tests and performance in a novel interface may seem distant, but they do share a common mental ability. When users pick up a new mobile phone or try to use a ticket kiosk in a foreign train station they are carrying out mental processing similar to answering the reasoning test: examining the options on the screen and then trying out different options to discover the next logical step. Unfortunately pure reasoning ability (as best as psychologists can measure it) also shows decline with aging with declines starting as early as age twenty (Figure 4.8).
Generally, making displays easier to use involve reducing the level of uncertainty about what to do next in the task so that reasoning ability is less of a factor in success. This could mean being more specific about the purpose of each task step and the consequences of actions as well as informing the user of their overall progress (for example, making explicit the number of steps remaining). Using icons that are less abstract and more representative of their function or task can also reduce the level of uncertainty.
However, it is rare to encounter everyday situations where one has no prior knowledge or experience and pure abstract reasoning is required. Instead, users usually always bring some amount of information or experience to these situations and use their prior knowledge to gauge expectations and guide behavior. This “mental set” is a particular way in which people approach and solve problems that is informed by prior experience or knowledge (everyday intelligence or cognition). This is why creating displays that act in ways users expect will reduce the need for reasoning ability.
184.108.40.206 Spatial Ability
Spatial ability helps a person mentally manipulate location-based representations of the world. This ability is important for reading a map of an unfamiliar city or trying to orient oneself by using the navigation system in a vehicle car. In these kinds of tasks, users transform, rotate, and manipulate the physical environment in their head. People also need spatial ability when they create or manipulate mental models. A mental model is a mental representation of a physical system—a map of sorts. For example, some people have mental maps of the layout of their childhood home or neighborhood. The mental map allows them to navigate the area quickly and may even facilitate the discovery and usage of “shortcuts” that speed navigation. In one test for spatial ability, the cube comparison test, the respondent has to decide whether the two cubes shown represent the same cube, but sitting on another face, or a completely different cube. Arriving at an answer quickly depends on the respondent’s spatial abilities.
Researchers have found that spatial ability is critical in the use of some kinds of computerized interfaces and tasks such as browsing the Web. For example, imagine the situation where a user browses a deep hierarchy (e.g., the Amazon.com online store). At a certain point, the user needs a mental model or map of the system so they know where they have been. The presence of the map allows users to more easily navigate the information hierarchy because it precludes the need for the user to create their own mental versions, but such a map is harder to create for older users.