Cumulative Recorder

 Wilhelm Wundt's experiments in the Konvikt laboratory allowed psychology to become a real science, thanks to the use of the newly invented instruments that permitted for a proper recording of the experimental data. Until that point, only theoretical divagations were taking place, with no actual proof. But with the dawn of the Industrial Revolution, more and more devices were showing up on the market that were designed to work as research aids. Early psychologists had their hand forced, and along the new theories they had to invent new devices that would allow them to measure whatever they were trying to prove as well.

The cumulative recorder is one of this creations. Invented by B.F Skinner, the founder of the Radical Behaviorism, it revolutionized the way in which animal behavior could be measured, allowing for precise documentation of all the events (like lever presses) along with a straight-forward axis-based visual depiction of the timeline. Even from a quick look at the data paper, some trends can be noticed right away. If the line was steep - the response rate was high, if shallow - the opposite. Every instance of the reinforcer being present was clearly noted. From the data analysis point, this was a huge step forward for the whole discipline and modern variations of it are still commonly used to this day. Smithsonian Museum owns one of the early commercial models build for Skinner, but it is currently not on a display anywhere.

The instrument itself is ingenious in its simplicity. This uncomplicated mechanism consists of a roll of paper that moves at an unchanged pace and a pen that draws a line across it. With every response from the participant, the pen moves slightly in the upwards motion. That is why the angle of the line is a dead giveaway - the more responses, the faster the pen will travel and the steeper the line will be.
Seeing data visually presented like that allows for some instant simple conclusions that would require time-consuming calculations in a numerical form, speeding up the progress of the research quite substantially.