n.1. any tool, device, or other means by which researchers assess or gather data about study participants. Examples include tests, interviews, questionnaires, surveys, rating scales, and reaction-time apparatus. See also assessment instrument. 2. in general, an implement used in performing specific operations, such as cutting or writing.
a hypothesis of perception of stimulus intensity, stating that a wide range of intensity values can be encoded by a group of cells, each of which is a specialist for a particular range of stimulus intensities.