Apparently, you can tickle animals and generate a lot of vocal activity that is assumed to be laughter. In the case of rats...they would let off a noise outside of our audible range, but can be heard through a transducer. The rats end up enjoying itself so much it would start playing with the hand and start chasing it seeking out more.

http://www.youtube.com/watch?v=myuceywaOUs

 

no ****!!! thats pretty cool, i'm a huge science nerd and LOVE stuff like that.

 

haha Rat tickler.

 

That is pretty cool! So what theyare saying is children are just like rats.