n. the design of a clinical trial in which part of the experiment would be to include blank items as a variable (the catch). For example, there is an interval in an auditory test (e.g. audiometry) wherein no actual signals are given but the participant's responses are recorded anyway. See blank trial.
CATCH TRIAL: "A catch trial helps correct the possibility of guesswork, especially in tests which require a simple yes-or-no response."