The Dumb Grenades were developed by the Department of Experimental Experiments, and are currently stored in the Department of Experimental Experiments's super secret disguised corridor are designed to reduce the target's IQ to a negative level for a brief period, causing the victim/target to act like a toddler.
First postulated by /u/Avengier_Than_Thou, the dumb grenade began when he walked in on 2 interns making a house of cards with a difference. Avengier then began experimenting with the concept but was asked by HR to stop blowing up interns because the janitor was complaining about the mess. As a result the concept was shelved for a while as Avengier was on his 20,153th intern of the month and the disposal chute was clogged.
After a break from the project it was revisited, but in an uncharacteristic show of compassion Avengier decided not to return to his messy antics and started considering less than lethal weaponry for use on interns that had annoyed him at times when he wasn't in the mood for dismemberment.
Out of this the concept of intelligence inhibiting munitions was born however during a test Avengier was caught by a blast and forgot the name or purpose of the device and started posting them to other departments labelled 'Pineapples that pop' nearly causing the destruction of the facility when the security chief ordered all interns shot on sight, luckily no one remembered the incident after the effects had worn off. Not knowing what the purpose of the device was and after failing to blow up an intern with one Avengier labelled them "Dumb Grenades" and consigned them to the departments storage rooms, however it is rumoured that he keeps a stock in his desk draw for when he gets particularly annoyed at someone. however it is thought that several others have gained access to the room they are stored in and they are now one of the most common weapons in the Facility.