of the comparison tasks

requirements with the task of interest. It should always keep in mind that the task chosen as presumably simple could actually not be such, or may have in common with the task of interest some components, without the investigator's knowledge. Many researchers use standard basic tasks in all their studies, whatever the objective of the survey. This makes it easier to find common activation patterns in much different research and opens the possibility for future meta-analysis. Regardless of the choice of the basic task, it is of primary importance to be aware of the cognitive operations required by the task, as well as of the other in which the subject may engage. Choice of comparison tasks The comparison tasks are more complex, often high-level, chosen because they differ in some specific way from the primary task of interest (in which case they are) or because they share important features with it, or for both reasons. A functional decomposition of the primary task of interest can identify functional characteristics that should be shared or absent .
http://healthnbeautyfacts.com/cogniflex/