In Wertheimer's tachistoscope experiment, what did subjects perceive when two lines were presented rapidly?

In Wertheimer's tachistoscope experiment, the focus was on the phenomenon of apparent motion and how the human visual system processes visual stimuli. When two lines are presented rapidly in a manner that they seem to be in close temporal succession, subjects perceive them as two lines appearing simultaneously rather than as distinct occurrences.

This perception occurs because the human brain interprets the rapid succession of visual stimuli in such a way that it synthesizes them into a single experience, leading to the impression of simultaneity. This finding was pivotal in demonstrating how perception is not merely a passive reception of stimuli but is instead an active process where the mind organizes and interprets what is seen. Wertheimer’s work became foundational in the field of Gestalt psychology, emphasizing the importance of holistic processing in perception.