The amount of pupil dilation (also known as "pupillometry") is believed to provide a relatively precise measure of the amount of mental effort associated with a task. Pupil dilation tests became a staple of advertising copy testing during the 1970s as a way to test consumers' responses to television commercials. Pupil dilation suggests a stronger interest in the stimuli and can be associated with arousal and action. Pupil dilation is not only used to study advertising, but also used to investigate product and package design.