The Dowsing Rod is an item in Psychonauts. It can be used to seek out deep arrowhead caches that are worth much more than ordinary arrowheads. This item can be purchased in the camp store in the Main Lodge for 50 arrowheads starting from PSI Cadet Rank 10.
The Dowsing Rod is not specifically required to beat the game, but collecting the 800 arrowheads necessary to purchase the Cobweb Duster (which is necessary to gain access to the Milkman Conspiracy and further levels) is nigh impossible and extremely tedious without having the Drowsing Rod, which makes it dramatically easier to do.
To find deep arrowheads, run around the campgrounds with the dowsing rod equipped listening to the sound. The rod will glow purple when pointed in the direction of a nearby arrowhead cache, and the sound it emits will increase in pitch the closer you are to an arrowhead cache. Follow the purple glow to the spot where the pitch of the sound is highest and rapidly hit the use key to extract the arrowheads.
- Ford Cruller says this item is worth the money because "it helps get money".