Poly-deficiency

I like to think that I understand dogs.  Their behaviors often follow a 'cause and effect' kind of relationship.  Cats, however, play by a different rule game alltogether and are in the realm of things I'll never fully understand (also in this realm: car mechanics, organic chemistry, and losing socks to the dryer...)

Oliver is our resident feline.  Since the canine invasion, his life has been reduced to finding dog-proof areas to hide (typically buried in closets or under blankets) and almost nightly games of 'chase the hairtie down the hallway.'  This little guy has some odd habits.  He enjoys pestering people while in the bathroom, drinking from the toilet, sitting on the scale, loves lapping up water from the shower and has an obsession with plastic. 

Oliver- caught in the act

We joke that the plastic-licker is poly-deficient and therefore requires additional intake of some form of polymers.

Why do cats do that?  Is there any science behind the feline plastic-lickers of the world?  I've not yet found any factual explanation for this behavior-- only a few hypotheses.  These include the thought that there might be a slight odor in the plastic that is simply irresistible to cats, that cats like the texture, or just an oral compulsive behavior....

...the world may never know.