Before the advent of commercial tape recorders, you had to get a little creative if you wanted to listen into unsuspecting teenage uni students' conversations without their knowledge or consent.
In 1938, a group of psychologists wanted to explore a question about language: are adults just as egotistical as toddlers. They believed that as people get older, they stop using such "egocentric" speech, such as interacting information about themselves constantly into the conversation. Aside from the mystery of how they had become professors of psychology without having ever met a person, they also had to solve another problem if they were to find this out: how do we listen in on people's conversation without ruining the study with our presence?
The answer, or part of it, was to stalk the streets, eavesdropping on whoever they could while taking notes.
"Remarks were collected in waiting-rooms and hotel lobbies, streetcars, theatres and restaurants," they wrote in their study, which is kind of fine. "Unwitting subjects were pursued in the streets, in department stores, and in the home" which was a little more morally ambiguous.
Where they really jumped the ethical line, however, was when they casually decided to hide under the beds in students' rooms.
Concealing themselves like the bogeyman, the psychologists slithered under the beds and waited there with their notepads, ready to eavesdrop on some kids. Hidden there, like, let's face it, some sort of murderer, they waited until the students had a tea party and took quiet notes from their hidey holes.
It's unclear how valid they expected the conversations recorded under the bed to be when the students were clearly going to be talking loudly and trying to act normal while one of them contacts the cops. However, the data that they did get was pretty unusable.
When they were merely stalking people through the streets, or listening into the bathrooms of the students (another thing they did), or listening in to their telephone calls (again, if it isn't already clear, these people didn't care about privacy) they were able to take notes of conversation every 15 seconds. Under the bed, they couldn't do this for fear of the kids saying "hey what the hell is that scratching noise every 15 seconds".
As such, they ended up having committed some sort of light crime (I assume the penalty for hiding under someone's bed and recording them without their knowledge isn't a policeman saying "get out of here you little scamp") for no real reason whatsoever.
Thankfully, they had collected enough data from hanging out in the students' toilets and listening in to their phone calls to determine that they too were as self-obsessed as toddlers.
"The present study shows that adults talk about themselves, their activities and their views, to as great an extent as do children," they concluded.
But considering what they'd done to figure that out, I'd say how dare you be so judgy.