Toward An Understanding of Universal Ethics via Agreement Between Dog and Human Ethics

Just in case you're wondering, this is not satire.

Our dog is fed twice per day but always (unless it runs out and we don't notice) has water available.

Her behavior with regards to these two essential things could not be more different:  

When it comes time to be fed, or really anytime when food is in-play, she becomes very excited and seems to welcome 'tasks' in exchange for food.  Sometimes when she is uninterested in her kibble, I will have her do tricks with a kibble reward.  Or have her chase-down a kibble piece that I toss across the room.  (She really likes it when I toss a piece under the dining table.  She has to do dog-geometry to negotiate all of the chair and table legs. This gets her excited and soon, she wolfs-down her bowl of kibble.

With water, she is never excited--she goes and drinks as she needs to. Every once in a while we let the bowl run dry and we find out because she will just lay down near it and look pathetic.  We feel so sad!  How could we neglect her like this?  When we are in the process of re-filling the water bowl, she is attentive but not excited like she would be with food.

I brought this difference with my wife.  We both agreed that it would feel wrong to make her do tricks for water.  The dog 'feels' the same way.  Logically, both are essential to life, but on an emotional level they are different.  The dog and the Humans agree on this, so maybe, while it's hard to define why, there is something fundamentally different.  We're not sure what it is but we are pretty sure that it is.