Subject: Why do partially deflated balloons contract when touched?

Take a latex balloon filled with air and tied on the end. Leave it sitting in a room until it deflates on its 
own. Once the balloon reaches a point at which it is roughly one third the total inflated size, the surface 
of the balloon will contract when touched with a bare hand. Hardly any pressure is needed to observe 
the reaction. The surface of the balloon instantly shrinks at the point of contact and only at the point of 
contact. Here is a photo of a touched balloon: http://www.zoelledesign.com/balloon.jpg

Re: Why do partially deflated balloons contract when touched?