Messick (1994) distinguishes between a task-centered and a construct-centered approach to assessment design, the latter being the approach espoused here. With a task-centered approach, the focus is on having students perform meaningful and important tasks, and the target of inference is, implicitly, the tendency to do well on those tasks. Such an approach makes sense under certain circumstances, such as an arts contest or figure-skating competition, when evaluation of the product or performance per se is the focus. But educational decision makers are rarely concerned with one particular performance. They tend to be more interested in the underlying competencies that enable performance on a task, as well as on a range of related activities. In such cases, a construct-centered approach is needed. Such an approach starts with identifying the knowledge, skills, or other attributes that should be assessed (expressed through the model of learning), which then guide the selection or construction of relevant tasks and scoring procedures. Messick notes that the movement toward performance assessment in the last decade has often been task-centered, with an emphasis on creating assessment tasks that are “authentic” and representative of important activities students should be able to perform, but without specification of the underlying constructs that are the targets of inference. Simply because a task is “authentic” does not mean it is a valid observation of a particular construct (Baker, 1997).
A related point is that design should focus on the cognitive demands of tasks (the mental processes required for successful performance), rather than primarily on surface features, such as how tasks are presented to students or the format in which students are asked to respond. For instance, it is commonly believed that multiple-choice items are limited to assessing low-level processes such as recall of facts, whereas performance tasks elicit more complex cognitive processes. However, the relationship between item format and cognitive demands is not so straightforward. Although multiple-choice items are often used to measure low-level skills, a variety of item formats, including carefully constructed multiple-choice questions, can in fact tap complex cognitive processes (as illustrated later in Box 5–7). Similarly, performance tasks, usually intended to assess higher-level cognitive processes, may inadvertently tap low-level ones (Baxter and Glaser, 1998; Hamilton, Nussbaum, and Snow, 1997; Linn, Baker, and Dunbar, 1991).
Linking tasks to the model of cognition and learning forces attention to a central principle of task design—that tasks should emphasize those features relevant to the construct being measured and minimize extraneous features (AERA et al., 1999; Messick, 1993). This means that ideally, a task will not measure aspects of cognition that are irrelevant to the targeted performance. For instance, when assessing students’ mathematical reasoning, one should avoid presenting problems in contexts that might be unfamiliar to a particular population of students. Similarly, mathematics tasks should