Answer:
subliminal perception.
Explanation:
Subliminal perceptions, also known as subliminal messages, are messages, either visual or auditory, that are presented just beyond the threshold of human perception. A subliminal perception may not be audible enough that the conscious mind might register it but be audible enough for the subconscious mind.
For example it might be an image transmitted briefly and unperceived consciously and yet perceived unconsciously.
Observation designed to minimize the effects of variables other than the independent variable.
