Rats laugh when you tickle them

as seen on huffington post and abc news.  In this video you can observe rats laughing at a higher pitch than humans can hear.  In order for humans to observe the sound at a pitch that we can hear a transducer is used.  One can use a bat detector to do this as it has the same basic function and range required to hear rats communicate/laugh on a higher pitch than we can otherwise hear.

Wondering if your pet rat is ticklish and don't have a bat detector laying around?  You can buy a generic bat detector  for around $90 or if you enjoy simple electronics projects you can make one very inexpensively.