sentences:  In the early 1980s the shift in analytical perspective from thinking of a commercial as the fundamental unit of measurement to be rated in its entirety, to thinking of it as a structured flow of experience, gave rise to experimentation with moment-by-moment systems.The most popular of these was the dial-a-meter response which required respondents to turn a meter, in degrees, toward one end of a scale or another to reflect their opinion of what was on screen at that moment.More recently, research companies have started to use psychological tests, such as the Stroop effect, to measure the emotional impact of copy.