Answer: The meaning of a new stimulus
Explanation: The non-matching-to-sample task is used to study Short-term memory for learned associations. This non-matching-to-sample task is a test used in animals to examine working memory.
It is done by presenting an animal with a sample stimulus, after a short time, the sample stimulus along with another new stimulus is presented to the animal. In non-matching-to-sample the animal is rewarded for selecting the new stimulus.