1. the tendency for items to be consistently grouped together in the course of recall. This grouping typically occurs for related items. It is readily apparent in memory tasks in which items from the same category, such as nonhuman animals, are recalled together.

2. in statistics, see cluster analysis.

3. in ergonomics, a method of knowledge elicitation in which a researcher interviewing users of a product or system jots down key ideas or words as they occur and then groups together linked ideas and meanings. The clusters so formed are then used to create taxonomies, task hierarchies, or menu structures. —cluster n., vb.