Editing Usability (section)

====Human processor model====
{{main|Human processor model}}
Sometimes it is useful to break a task down and analyze each individual aspect separately. This helps the tester locate specific areas for improvement. To do this, it is necessary to understand how the human brain processes information. A model of the human processor is shown below.

[[File:HumanProcessorModel.svg]]

Many studies have been done to estimate the cycle times, decay times, and capacities of each of these processors. Variables that affect these can include subject age, [[aptitude]]s, ability, and the surrounding environment. For a younger adult, reasonable estimates are:

{| class="wikitable"
|-
! Parameter
! Mean
! Range
|-
| Eye movement time
| 230 ms
| align="right" | 70–700 ms
|-
| Decay half-life of visual image storage
| 200 ms
| align="right" | 90–1000 ms
|-
| Perceptual processor cycle time
| 100 ms
| align="right" | 50–200 ms
|-
| Cognitive processor cycle time
| 70 ms
| align="right" | 25–170 ms
|-
| Motor processor cycle time
| 70 ms
| align="right" | 30–100 ms
|-
| Effective working memory capacity
| 2 items
| align="right" | 2–3 items
|}

Long-term memory is believed to have an infinite capacity and decay time.<ref>Card, S.K., Moran, T.P., & Newell, A. (1983). ''The psychology of human-computer interaction''. Hillsdale, NJ: Lawrence Erlbaum Associates.</ref>